### PARTIAL OUTPUT (time limit hit; the model was still generating) ###

=== thinking so far ===
I'm building a complete falling-blocks puzzle game in a single self-contained HTML file. Let me think through everything I need:

**Core requirements:**
- 10×20 playfield on canvas
- 7 tetromino shapes (I, O, T, S, Z, L, J), 4 squares each, distinct colors
- Controls: ←/→ move, ↑ rotate, ↓ soft drop, Space hard drop
- Rotation with wall/stack collision (no clipping) — I'll implement proper rotation with simple wall-kick attempts (offset 0, -1, +1, -2, +2)
- Line clears with cascade, scoring for multi-line clears
- Score/lines/level display, speed increases with level
- Next piece preview box
- Game over detection, visible state, restart key (I'll use "R" and also allow clicking)
- Clean dark style

**Architecture decisions:**

I'll use vanilla JS with two canvases (main board + next-piece preview) or one canvas with regions. Actually, let me use one main canvas for the playfield, and a separate small canvas for the next-piece preview embedded in a sidebar. Sidebar will contain: title, next preview, score/lines/level stats, controls legend.

**Visual design thinking:**

Dark, clean, readable. I want this to feel like a genuinely crafted retro-modern puzzle game, not a generic template. Ideas:

- Deep charcoal/near-black background (#0d0f12 range), with a subtle grid on the playfield.
- Block colors: I'll pick a curated palette — not default neon Tetris colors but a tasteful set that still distinguishes the 7 pieces clearly. Something like a refined palette: cyan, amber, violet, green, red, blue, orange... Actually the classic colors are fine but I'll tune them to look good on dark: slightly desaturated but vivid.
- Blocks rendered with a subtle inner highlight/bevel — I can do a nice flat-but-dimensional look: fill color, darker border stroke, a lighter top-left edge, and a slightly darker bottom-right. That gives tactile quality without gradients as decoration (bevels on game blocks are functional shading, which is legitimate game rendering).
- Ghost piece: show where the piece will land (subtle outline). This is a nice touch for craft.
- Locked blocks could flash briefly on clear; cleared rows flash white then collapse. I'll implement a short clear animation (rows flash, then remove). To keep code simpler I can do a quick flash over ~200ms using a game phase system. Let me implement a small state machine: 'playing', 'clearing' (with timer), 'gameover'. During 'clearing', animate flash on the cleared rows, then shift.

Actually to keep things reliable, I'll implement the clear animation: when lines detected, set state to clearing with a 250ms timer, store the row indices, draw those rows with white/bright flashing (alternating), then after the timer, remove rows and continue. Input during clearing: allow left/right/rotate? Simplest to pause piece control during clearing (there's no active piece during clearing anyway — I can clear lines after lock and before spawning next piece).

Flow:
1. spawn piece → update bag
2. during play: gravity ticks based on level speed, movement, rotation, soft/hard drop
3. lock: merge into grid, check lines
4. if lines: flash animation → remove, score, maybe level up → spawn next
5. if no lines: spawn next immediately
6. game over check: if spawn position collides → gameover

**Gravity / speed:**
Speed via level: classic formula. Level increases every 10 lines. Drop interval: I'll use something like `interval = Math.max(60, (20 - level) * 50)`? Let me use a smoother curve: base 800ms at level 1, decreasing: `interval = Math.max(70, 800 * Math.pow(0.85, level - 1))` — or the guideline formula: `interval = Math.max(1000 * Math.pow(0.8, level-1), 60)`. That gets slow to fall at high levels. I'll use: `Math.max(800 * Math.pow(0.82, level-1), 60)`. At level 10: 800*0.82^9 ≈ 800*0.167 ≈ 133ms. Fine.

Soft drop: move down one row per keydown repeat or per interval while held — I'll implement soft drop as reducing the interval drastically while ArrowDown is held (like 40ms) plus awarding +1 per soft-dropped row. Simpler: on ArrowDown keydown, immediately move down if possible, and while held, apply faster gravity. DAS (delay auto-shift) for left/right: implement auto-repeat with initial delay ~170ms then repeat every ~50ms — that makes movement feel responsive and professional. I'll implement this with a small input handler: keydown sets held state + immediate action + timestamps; in the game loop, process held moves after DAS delay.

Actually, keep it manageable but good: implement DAS. It's not too much code and dramatically improves feel.

Hard drop: space — drop to landing position, lock immediately, +2 per cell dropped.

**Rotation with kicks:**
Define shapes as arrays of 4 rotation states? Better: define base shapes with coordinates, and compute rotations mathematically. For O piece rotation does nothing. For S/Z/L/J/T/I pieces, I'll precompute 4 rotation states as coordinate sets to avoid floating errors — or use matrix rotation on a bounding grid. Precomputing states via rotate function on cell coordinates around a pivot is standard.

I'll define each piece as list of [x,y] cells plus pivot for rotation:
- Simplest robust approach: store shapes as coordinate lists, generate rotations by rotating 90° around a pivot point per shape. For I and O use special pivots (I rotates around grid points so it stays in its cells).

Standard technique: represent each tetromino as a 2D matrix and rotate the matrix. For odd-sized matrices (3x3 for J/L/S/T/Z), rotate the matrix; for I (4x4) rotate matrix; O (2x2) rotation = same. This is clean and avoids pivot math. I'll store pieces as matrices and have a rotateMatrix function (transpose + reverse rows). Precompute rotations once at startup into `SHAPES[piece].rotations[0..3]`.

Wall kicks: on rotate, try candidate offsets: [0, 0], [-1, 0], [1, 0], [-2, 0], [2, 0], and maybe [0,-1] (move up) as last resort. For I piece also try y shifts. Simple kick set: [[0,0],[-1,0],[1,0],[-2,0],[2,0],[0,-1],[0,-2]]. This isn't full SRS but satisfies "rotation must respect walls and stacked blocks (no clipping)". It works well enough. Also T piece can just use these.

**Piece definitions (matrices):**

I: 4x4:
```
[[0,0,0,0],
 [1,1,1,1],
 [0,0,0,0],
 [0,0,0,0]]
```
O: 2x2 [[1,1],[1,1]]
T: 3x3 [[0,1,0],[1,1,1],[0,0,0]]
S: [[0,1,1],[1,1,0],[0,0,0]]
Z: [[1,1,0],[0,1,1],[0,0,0]]
J: [[1,0,0],[1,1,1],[0,0,0]]
L: [[0,0,1],[1,1,1],[0,0,0]]

Spawn x: (10 - width)/2 floor → for 3x3: 3 (or 4?). Standard: spawn at columns 3 for 3-wide (cells occupy cols 3-5), I at cols 3-6 with matrix width 4 → spawn x = 3. (10-4)/2 = 3. For 3x3: Math.floor((10-3)/2)=3 → occupies 3,4,5 — slightly left of center, acceptable, or x=4? (10-3)/2 = 3.5 floor 3. Use Math.floor((10-w)/2)? For w=3 → 3; hmm center would be 4 with offset... 10 columns, 3-wide piece centered at cols 4,5,6? Actually center of 10 cols is between 4 and 5 (0-indexed 0..9), so a 3-wide piece should occupy 4,5,6? (10-3)/2 = 3.5, so 3 or 4 both fine. I'll use Math.floor((10 - w) / 2) which gives 3 for 3-wide and 3 for 4-wide — actually for w=4: (10-4)/2 = 3, occupies 3..6. Center-ish. OK.

Spawn y: -1 or 0? I'll spawn at y=0 with matrices that have their content in row 1 (I) or rows 0-1 (others). If spawn position collides immediately → game over. Also spawn slightly above (y=-1) so blocks appear to enter from top — with matrix rows, I'll allow y = -1 and handle negative rows in collision checks (cells above the board are always free unless x out of bounds). Collision function: cell y < 0 → only check x bounds; y >= 0 → check grid. Lock: if any cell y < 0 at lock → that's fine, just clip? No — lock above top means game over. Standard: game over when stack reaches top. I'll do: on spawn, if collision at spawn → game over. Additionally, on lock, if any cell is above row 0 (y<0), game over. Let me keep spawn y = 0 and check: if new piece collides at spawn → game over. That's simple and meets "stack reaches top".

Hmm, but with spawn y=0 and matrices where top row may be filled (e.g., T has content in row 0), pieces appear right at top — fine.

Actually, let me spawn at y=0 but give the visual board 20 rows exactly. Also allow y=-1 spawn: piece appears to slide in. I'll spawn y = 0 for simplicity; with spawn collision check → game over. That satisfies the requirement.

Wait — one subtlety: with spawn y=0, the I piece's filled row is matrix row 1, so it appears at board row 1. Fine.

**Grid storage:** 2D array rows × cols, storing 0 or color index (1..7). Use piece index for coloring.

**Scoring:** classic: single 100 × level, double 300 × level, triple 500 × level, tetris 800 × level. Soft drop +1/cell, hard drop +2/cell. Level: level = Math.floor(lines / 10) + 1. Speed from level.

**Next piece:** 7-bag randomizer (nicer than pure random, standard modern Tetris). Bag of 7 shuffled, refill when exhausted. Show next piece in preview canvas, centered.

Also I could show "hold" but not required — skip to keep scope tight. Maybe not; requirements are explicit. Keep focused.

**Ghost piece:** draw outline at landing position — great usability. Implement: compute drop position, draw semi-transparent cells / outlines.

**Rendering details:**

Canvas board: 10×20 cells. Cell size: 28px → 280×560. Plus I'll add subtle board background and grid lines. Page layout: centered flex, dark background, board with border/glow? No glow — keep it clean: a thin border, maybe a slight outer frame. Sidebar to the right: title "BLOX" or something, NEXT box, stats (score/lines/level), controls list, restart hint.

Fonts: I can't load Google Fonts? "no internet resources" — so no external fonts. Must use system fonts. I dislike defaulting to plain sans, but with no external resources I have to pick from web-safe stacks. I'll use a monospace stack (`ui-monospace, "SF Mono", "Cascadia Mono", Consolas, monospace`) — monospace gives a techy retro-terminal vibe appropriate for a puzzle game and looks intentional, especially for numbers/score. Title in monospace with letter-spacing looks sharp. That's a deliberate choice, not lazy default.

Color palette for pieces (distinct, tuned for dark bg):
- I: teal/cyan #56c8d8 → I'll pick: 
- Let me choose a cohesive palette with slightly muted-saturation vivid colors:
  - I: #5fd3c6 (teal)
  - O: #f2c94c (amber)
  - T: #b184e6 (violet)... purple pieces fine (it's a game piece color, not UI decoration)
  - S: #8ddb4f? Let me refine: S green #77d97b, Z red #ef6b6b, L orange #f09a4e, J blue #6ea3f2.
  
Let me finalize:
- I → #63d6d0 (teal)
- O → #f5c65a (amber)
- T → #c08bf2? make it #b586f0 violet
- S → #7ee08a green
- Z → #f26d6d red/coral
- L → #f2a35c orange
- J → #71a4f0 blue

These read well on dark. Blocks: fill with color, 1px darker inner border, top edge lighter strip, bottom darker — a subtle bevel. Plus rounded? Slight radius (2px) could look modern but adjacent blocks with gaps look nicer with tiny 1px gap or a dark gap grid. Classic Tetris style: blocks fill cell fully with bevel. I'll render cell at size-2 with 2px inset so grid lines show subtly? That creates a nice tiled look. Let me do: cell draw with 1px inset (drawn at x+1, y+1, size-2, size-2) with a 2px rounded corner? Keep it: inset 1, small radius 3, fill color, then a highlight: semi-transparent white overlay rectangle on top portion (alpha 0.18) — that's shading, functional. And stroke with rgba(0,0,0,0.35) inner. This gives crisp candy blocks.

Background of board: #101318 slightly different from page bg #0b0d10. Grid lines rgba(255,255,255,0.04).

Game over: overlay on canvas — dim board, show "GAME OVER" text and "press R to restart". I'll draw on canvas or a positioned HTML overlay. Canvas overlay drawn in the render loop is fine.

Also add pause? Not required — skip. Maybe "P" pause would be nice but scope; I'll skip to keep the file focused. Actually a small pause could be nice... I'll skip — requirements only ask restart key.

**Line clear animation:** when lines found: state = 'clearing', store rows, timer 300ms; render those rows flashing: alternate fill white with alpha based on time; then after timer, splice rows, add empty row at top, apply score/lines/level, spawn next piece. During clearing, active piece is null so no updates. Also sound? No audio requirement; could add WebAudio beeps... optional. Small tasteful addition: tiny WebAudio blips for lock/clear — but "no internet resources" fine since WebAudio is local. It adds life. But it might add complexity; I'll add a minimal synth: function beep(freq, dur, type). Keep volume low, and wrap in try/catch, plus only start AudioContext after first input (autoplay policy). I think it's worth it — adds juice. Keep it tiny (~15 lines).

Hmm, should I? The requirement list doesn't mention audio. Adding subtle audio enhances "alive" feel. I'll include it but keep it minimal and non-intrusive. Also a "M" mute key? Extra scope... I'll skip mute toggle, keep sounds subtle. Actually, let me add mute with "M" — trivial (one boolean). Fine, list it in controls.

**Input handling with DAS:**

- keydown: track keys held (Set or object with timestamps).
- Left/Right: on keydown → move + record time; in update loop: if held longer than DAS (160ms) then move every 45ms (repeat timer).
- Up: rotate on keydown only (prevent repeat via key event repeat check — ignore e.repeat for rotation, or track keyup). I'll ignore e.repeat for rotate and hard drop.
- Down: keydown sets softDropHeld=true; update loop: soft drop interval = 45ms; also immediate move on keydown. On keyup, clear flag. Score +1 per soft drop row moved.
- Space: hard drop (ignore repeat).
- R: restart anytime. M: mute.
- preventDefault on arrows/space to avoid page scroll.

Movement handling inside fixed update: I'll structure the loop with requestAnimationFrame and accumulate time. Piece gravity: accumulate dt; while acc >= interval → step down. Movement (DAS repeats) processed per frame using timestamps.

Implementation plan for loop:

```
let last = performance.now();
function frame(now){
  const dt = Math.min(now - last, 100); last = now;
  update(dt, now);
  render(now);
  requestAnimationFrame(frame);
}
```

update(dt, now):
- if state==='clearing': timer -= dt; if <=0 → finishClear();
- if state==='playing' and piece exists:
  - handle DAS: if dir held: if now - dasTime >= DAS: while now - dasTime >= DAS + repeatCount*REPEAT... simpler: maintain `lastRepeat` timestamp; if held && now-dasStart>DAS && now-lastRepeat>=REPEAT → move, lastRepeat=now. Cleaner: on keydown: move once; dasStart=now; repeatAt = now+DAS. In update: if held and now>=repeatAt: move; repeatAt = now + REPEAT. If both left/right held, use last pressed direction (track lastDir by most recent keydown).
  - soft drop: if downHeld: acc with softInterval; effectively use interval = softInterval while held; award points for rows descended via soft drop — track how: when gravity step occurs while downHeld, score+=1 per row. But gravity steps also happen naturally... To distinguish: use separate accumulators? Simpler: piece gravity accumulator; effective interval = downHeld ? SOFT : gravityInterval. When a down-step occurs (interval elapsed) and downHeld → +1 score per row. Also the immediate move on keydown → +1 if moved. Hmm slight ambiguity fine: award +1 for each row gained while soft dropping. I'll count: when downHeld and piece moves down via soft mechanism → score += rows moved. For the keydown immediate move: +1 per row moved.
  - gravity accumulator: gravAcc += dt; while gravAcc >= interval: try move down; if can't → start lock. Lock delay? Implement lock delay ~ 500ms when piece can't move down (grounded), resets on move/rotate — this is modern Tetris craft. Or lock immediately on gravity step when grounded? Classic behavior: lock on next gravity tick when blocked. Lock delay makes it feel better. I'll implement: if piece grounded (can't move down), start lockTimer (500ms); if any successful move/rotate/soft-drop resets... full "move reset" limit to prevent infinite stall: cap resets at like 8? Simpler: reset lock timer on successful lateral/rotate movement but max 7 times per piece... That's extra complexity. Compromise: lock delay 500ms, reset on move/rotate without cap — risk of infinite stall is user-driven (they'd have to keep moving deliberately); acceptable. Actually infinite stall only while they keep pressing; once they stop, 500ms later it locks. Fine, no cap needed.

Let me simplify: when gravity step attempts move down and fails → if lockTimer not started, lockTimer = LOCK_DELAY(500ms as ms accumulator). Then each update: if grounded, lockTimer -= dt; if <=0 → lockPiece(). Successful lateral move or rotate or soft-drop step down → lockTimer = LOCK_DELAY if grounded (reset). When piece moves down (gravity or soft), clear lockTimer (grounded false) and reset gravAcc.

Hard drop: while canMove(0,1) move down; score += 2*rows; lock immediately.

lockPiece(): merge cells into grid (with color index). If any cell y<0 → gameOver. Check lines → if lines: state='clearing', flash rows, store; else spawnPiece(). Play sound.

finishClear(): remove rows (filter + unshift empty), update lines/score/level, spawnPiece(). Note: level could change speed — recompute interval.

spawnPiece(): take from queue (refill bag when needed; keep queue of next 1 + current? I'll maintain `bag` array; next piece = bag[0]; when spawning, shift and refill bag if length < 2? To show next, keep at least 2. Implementation: function refill(){ if bag.length < 7 ... } Standard: keep bag as queue, refill by pushing shuffled 7 when bag length <= 1? Let me do: `function nextFromBag(){ while(bag.length < 2) bag.push(...shuffle(PIECES_KEYS)); const k = bag.shift(); ... }` Actually ensure bag has at least 2 entries always: refill to 7 when below 2. Fine.

piece = {key, matrix rotations index, x, y}. I'll store piece as {type, rot, x, y} and lookup cells via SHAPES[type][rot] precomputed.

Rotate: rot = (rot+1)%4; candidate cells = SHAPES[type][newRot]; try kicks offsets; if any works, apply. Reset lock timer if grounded. Sound blip.

collides(cells, x, y): for each [cx,cy]: bx = x+cx, by = y+cy; if bx<0||bx>=COLS||by>=ROWS → true; if by>=0 && grid[by][bx] → true. (by<0 allowed.)

Ghost: dropY = y; while !collides(cells, x, dropY+1) dropY++.

**Render:**

- Clear canvas, draw bg, grid lines.
- Draw locked cells.
- Draw clearing flash rows (if clearing: overlay on those rows with white flashing alpha).
- Draw ghost (outline stroke per cell, alpha low).
- Draw active piece.
- If gameover: dim overlay + text. Also set a flag so board shows final stack.

Preview canvas: 80x80? Piece 4x4 max → cell 20px → 80x80 plus padding. Draw next piece centered: compute bounding box of cells and center it. Use same block renderer.

**Sidebar HTML:** 

- Header: game title — I'll name it "TETRA·GRID"? Something like "BLOCKFALL". Keep monospace, letter-spaced. Maybe a small accent square motif next to title (a tiny 4-block tetromino glyph rendered via CSS spans — could be nice signature). I'll render a small "T" tetromino made of 4 divs next to the title — nice authored touch.
- NEXT label + canvas.
- Stats rows: SCORE / LINES / LEVEL with values in tabular numerals (monospace handles it).
- Controls list with key caps styled as `<kbd>` elements.
- Speed indicator? Level implies speed. Maybe a subtle "speed" bar? Skip.
- Footer hint: R restart · M sound.

Layout: flex row, board left, panel right (width ~180px). On narrow screens, stack. Page bg #0b0d10 with maybe a very subtle texture? Keep flat dark. Panel separated by border-left or just spacing; panel bg slightly lighter (#12151a) with rounded corners and border. Title monospace uppercase letterspaced, small accent color? Accent: use teal (#63d6d0) sparingly for the title or values. Keep restrained.

**Line clear animation:** flash: during clearing, cleared rows drawn as bright white with alpha oscillating (sin of elapsed) → then a quick collapse. 300ms flash. I'll pass elapsed to render via clearingStart timestamp + remaining timer. Simpler: store clearing = {rows, timer, total}. Alpha = timer/total (fades) or flashing: alpha = 0.5 + 0.5*sin(...). I'll do: rows filled with white, alpha = 0.4 + 0.6 * (timer/total) fading plus a slight strobe? Keep simple: fill white with alpha = timer/total → fades out, then rows collapse. Good enough and clean.

Also on clear, small screen "pop": draw the rows white fading. Fine.

**Sounds (WebAudio):**
```
let audioCtx=null, muted=false;
function blip(freq, dur=0.06, type='square', vol=0.04){
  if(muted) return;
  try{ audioCtx = audioCtx || new (window.AudioContext||window.webkitAudioContext)();
    const o=audioCtx.createOscillator(), g=audioCtx.createGain();
    o.type=type; o.frequency.value=freq; g.gain.value=vol;
    o.connect(g); g.connect(audioCtx.destination);
    o.start();
    g.gain.exponentialRampToValueAtTime(0.0001, audioCtx.currentTime+dur);
    o.stop(audioCtx.currentTime+dur);
  }catch(e){}
}
```
Calls: move: blip(220, .03, 'square', .02)? Movement sounds every DAS repeat could get noisy — make move silent or very quiet; rotate blip 330; soft drop step? silent; lock: blip(180, .08, 'triangle'); line clear: sequence blip(520), blip(660) via setTimeout or quick arpeggio; hard drop: blip(140). Game over: descending notes. Keep subtle. Initialize AudioContext on first keydown (user gesture). I'll create ctx lazily inside blip (called from input handlers → user gesture satisfied).

**Restart:** R key resets all state: grid empty, bag refilled, score/lines/level reset, spawn piece, state='playing'. Also allow clicking a "restart" text button? Requirement says restart key — R is enough, but I'll also make the game-over overlay say "PRESS R TO RESTART". Maybe also allow Enter. R suffices; I'll accept R and Enter.

**Game over condition nuance:** Also game over if a newly spawned piece collides immediately (stack reached top). Also on lock with cells above top (by<0 at lock) — actually if piece locks with any cell above the board, that means stack reached top. With spawn y=0, cells at by>=0 always at spawn; but pieces can be pushed up by kicks ([0,-1],[0,-2] offsets) — then a piece might lock with by<0. In lockPiece: if any cell by<0 → gameOver. But also those cells with by<0 shouldn't be written to grid (skip them). Let me handle: write cells only for by>=0; if any by<0 → gameOver state (draw stack as is). Also the alternative: standard — game over when spawn collides. Both.

Wait: kicks [0,-1] could push a piece above top where it can't be seen... edge case; only allow upward kicks when they keep cells visible? Simpler: include [0,-1] kick only... Actually upward kicks are needed for T-spin-ish situations near stack tops; but to avoid pieces locking off-screen, I could disallow by<0 cells in collide (treat by<0 as out of bounds → collide true). That means rotation near the very top is restricted — fine and safer. But then a piece spawning at y=0 with matrix top row filled (T at rot0 has row0 filled? T matrix [[0,1,0],[1,1,1],[0,0,0]] row 0 filled) — y=0 fine, by>=0. With by<0 treated as collision, spawn y=0 always valid if x fits. Good — treat by<0 as collision. But then I piece spawn: matrix row1 filled → by = 0+1 = 1. fine.

Hmm, but that makes the game-over check purely spawn-collision based. Good: "game over when the stack reaches the top" = new piece can't spawn. Also when locking, if piece cells are at row 0 and stack builds above? by<0 can't happen. OK: collide() returns true if by < 0. Game over only at spawn. That's clean.

Edge: hard drop can push pieces to lock with top row filled; next spawn collides → game over. Good.

**Board dimensions:** COLS=10, ROWS=20, CELL=28 → 280×560 canvas. Add devicePixelRatio scaling for crisp rendering — nice craft: set canvas width = w*dpr, style width w, ctx.scale(dpr,dpr). Do it for both canvases.

**Now, line clear detection:** rows where all cells nonzero → indices. 

**Scoring table:** [0, 100, 300, 500, 800] * level for 1..4 lines.

**Level speed:** gravityInterval(level) = Math.max(60, 800 * Math.pow(0.82, level-1))? Let me compute a table: L1 800, L2 656, L3 538, L4 441, L5 362, L6 297, L7 244, L8 200, L9 164, L10 134, L11 110, L12 90, L13 74, L14 60 (floor). Good progression.

Alternatively I might display a small speed bar in panel? Skip.

**Next piece preview:** canvas 96×96 (dpr-aware). Draw piece centered: compute min/max of cells, offset to center: cellSize 20? If I piece width 4 → 80px, fits in 96 with padding. cell = 20, offset = (96 - w*20)/2 etc. Compute from bounding box: minX,maxX of cells → w=(maxX-minX+1). Center: x0 = (96 - w*cell)/2 - minX*cell. Draw blocks with same style but maybe smaller bevel. Reuse drawBlock(ctx, x, y, size, colorIndex).

Also maybe show a queue of next 2-3 pieces? Requirement says "next-piece preview box" — one is enough; showing 2 could be nice but keep to spec: one box. Fine — I'll show just next (clean).

**HTML structure:**

```html
<!DOCTYPE html>
<html><head><meta charset viewport><title>Blockfall</title>
<style>...</style></head>
<body>
<main>
  <div class="board-wrap"><canvas id="board"></canvas></div>
  <aside class="panel">
    <div class="title-row"><div class="tetro"><i></i>...4 squares...</div><h1>BLOCKFALL</h1></div>
    <section class="box next"><span class="label">NEXT</span><canvas id="next"></canvas></section>
    <section class="box stats">SCORE/LINES/LEVEL rows</section>
    <section class="box keys">controls</section>
  </aside>
</main>
</body>
```

Title: "BLOCKFALL". Small tetromino glyph: 3x2 arrangement (T shape) via CSS grid with 4 cells colored accent. 

Stats values update via DOM (textContent) — cheaper than canvas text and crisper. Yes, update in JS.

Also a message line for game over? Overlay on canvas. Maybe also flash the panel? Keep canvas overlay.

CSS details:
- body: background #0b0d11; color #c7ccd4; font monospace stack; display flex center; min-height 100vh.
- main: display flex; gap 20px; align-items stretch.
- board-wrap: border 1px solid #2a3038; background #0f1318; padding 10px? Actually canvas itself has its own bg; wrap adds frame: border + slight padding 12px with bg slightly different, rounded 4px. Hmm — I'll give the canvas a 2px border (#262c34) and leave wrap padding minimal. Let me design: .board-frame { background:#11151b; border:1px solid #262d36; border-radius:6px; padding:14px; } canvas inside with border:1px solid #232a33.

- panel: width 190px; display flex column gap 14px. Sections .box { background:#11151b; border:1px solid #262d36; border-radius:6px; padding:12px 14px; }
- labels: 10-11px, letter-spacing 2px, color #7b8593, uppercase.
- values: 18-20px monospace, color #e8ecf1; score maybe teal accent #63d6d0? Keep values near-white; accent teal for NEXT label or title. Restraint: mostly neutral grays + one teal accent on active elements.
- kbd: display inline-block; background #1a2027; border:1px solid #333b45; border-bottom-width 2px; border-radius 4px; padding 1px 6px; font-size 11px; color #d7dce4.
- controls list: rows with kbd + description, small font 12px.

Title: font-size 15px letter-spacing 4px, color #e8ecf1, with the small tetromino in teal.

Responsive: @media (max-width 520px) → column layout, panel width auto, board scales? Canvas fixed 280px wide is fine on mobile-ish. Keep simple.

**Canvas board bg:** #0d1117-ish (#0e1218). Grid lines every cell rgba white 0.035. Also slightly stronger every 5 rows? Subtle. Maybe draw a faint vertical center? Keep uniform grid.

Block drawing:
```
function drawBlock(ctx, px, py, s, ci){
  const c = COLORS[ci];
  // base
  ctx.fillStyle = c;
  ctx.beginPath(); roundRect(px+1, py+1, s-2, s-2, 3); fill; // inset 1 → grid gap effect
  // bevel: lighter top
  ctx.fillStyle = 'rgba(255,255,255,0.22)';
  ctx.fillRect(px+2, py+2, s-4, 3); // hmm rounded corners overlap; simpler: fill a rect within
  // darker bottom edge:
  ctx.fillStyle='rgba(0,0,0,0.28)'; ctx.fillRect(px+2, py+s-6, s-4, 3);
  // inner stroke
  ctx.strokeStyle='rgba(0,0,0,0.4)'; stroke rounded rect? 
}
```
Rounded rect helper: use ctx.roundRect if available (Chrome/Safari/Firefox support roundRect now) with fallback path function. I'll write a helper `rr(ctx,x,y,w,h,r)` building path manually to be safe.

Bevel design: after base fill, draw a thin lighter strip along top and left (like a highlight) using 'rgba(255,255,255,0.25)' clipped inside; and dark strip bottom/right rgba(0,0,0,0.25). Implementation: use ctx.clip on the rounded path then draw highlight rect top (height s*0.28) and shadow rect bottom. Then stroke path with rgba(0,0,0,0.35), lineWidth 1.5? Actually simpler and still nice: fill base, then stroke inner rounded rect (inset 2) with rgba(0,0,0,0.3), then top highlight strip. Let me write:

```
function drawBlock(ctx,x,y,s,ci, alpha=1){
 const c=COLORS[ci];
 ctx.globalAlpha=alpha;
 ctx.fillStyle=c;
 rr(ctx,x+1,y+1,s-2,s-2,3); ctx.fill();
 // top highlight
 ctx.fillStyle='rgba(255,255,255,0.28)';
 rr(ctx,x+2,y+2,s-4, (s-4)*0.35, 2); ctx.fill();  // hmm this looks like a bar; maybe fine
 // bottom shade
 ctx.fillStyle='rgba(0,0,0,0.25)';
 rr(ctx,x+2, y+s-2-(s-4)*0.28, s-4, (s-4)*0.28-1, 2); ctx.fill();
 // border
 ctx.strokeStyle='rgba(8,10,14,0.6)'; ctx.lineWidth=1;
 rr(ctx,x+1.5,y+1.5,s-3,s-3,3); ctx.stroke();
 ctx.globalAlpha=1;
}
```
Hmm, the top highlight bar might look like a stripe — many Tetris implementations do exactly this "candy" look and it reads well. Let me refine: highlight strip height ~ s*0.3 at top with slight rounding; it's the classic beveled candy look. I think it will look good. Alternatively a subtle inner glow via radial? No — keep the stripe.

Actually, let me reconsider for a cleaner look: flat color with a 2px darker bottom+right edge (drop-shade) and 1px outline. Hmm. The candy bevel is iconic for Tetris and looks lively on dark. Keep bevel but subtle: highlight alpha 0.22, shade alpha 0.3.

Ghost rendering: stroke rounded rect outline with the piece color at alpha 0.35 + no fill? Or fill with alpha 0.08 + stroke alpha 0.4. I'll do: stroke color with globalAlpha .5, dashed? Keep simple stroke: `ctx.strokeStyle=c; alpha .35; rr(...); stroke;` per cell.

Active piece: drawBlock per cell.

**Flash overlay for clearing rows:** white fill alpha per timer.

Also subtle: when a piece locks, maybe leave slight flash? Skip.

**Pulse on level up?** Could flash the LEVEL value via CSS class — small DOM touch: add class 'bump' briefly. Nice micro-interaction: when score increases significantly or lines cleared, bump the stat. Simple: CSS animation transform scale. Add helper bump(el). Do it for lines/score on clear. Cheap and adds life.

**DAS constants:** DAS=150ms, REPEAT=40ms, SOFT interval=40ms, LOCK=500ms.

**Update pieces of logic — code structure:**

```js
const COLS=10, ROWS=20, CELL=28;
const COLORS = { I:'#63d6d0', O:'#f2c14e', T:'#b586f0', S:'#7ee08a', Z:'#f2696b', L:'#f2a05b', J:'#71a3f0' };
// matrices
const BASE = { I:..., O:..., ... };
const SHAPES = {}; // SHAPES[type] = [r0,r1,r2,r3] cell lists? Or matrices.
```

I'll precompute rotations as matrices then convert to cell lists with top-left normalized? If I keep matrices and origin at matrix's top-left, the I piece matrix width 4 and its row 1 filled — spawn x=3 gives cells at cols 3..6. For rotation as matrix: rotating a 3x3 matrix keeps bounding box; I 4x4 rotates within 4x4 box. When I rotates from vertical (state 1: column) to horizontal, the box stays 4x4, cells shift within. Standard. Rotation of matrix: rotate clockwise: `rotated[c][rows-1-r] = m[r][c]`? Let me define rotateCW(m): newM[c][m.length-1-r] = m[r][c]. Check with I: m row1 all 1 (r=1, c=0..3). newM[c][4-1-1=2] = 1 → column 2 filled at row 2 → vertical bar at col 2, rows 0..3. Good. Next rotation: from vertical (col 2 filled rows 0..3) rotate CW: newM[c][3-r]: for r=0..3 c=2 → newM[2][3-r] → row 3-r filled for r 0..3 → all row indices 0..3 at col 2 → hmm that gives row? Wait: newM[c][3-r]=m[r][c] → newM[2][3-r] = 1 for each r → rows 3,2,1,0 at col 2 → still vertical. That's wrong. Let me redo the formula.

rotateCW: result[r][c] = m[len-1-c][r]. Check: I horizontal row1: m[1][c]=1 ∀c. result[r][c] = m[3-c][r] → =1 iff 3-c==1 → c==2 → col 2 filled all rows → vertical at col 2. ✓. Rotate again: m now vertical col2: m[r][2]=1 ∀r. result[r][c] = m[3-c][r] → =1 iff 3-c is any row with col2=1 → 3-c==r? Wait m[3-c][r] = 1 iff m at row (3-c), col r =1; vertical piece has 1 at (row any, col 2) → so need r==2 and row 3-c ∈ 0..3 → always true → result[r][2]=1 ∀r → still vertical. Wrong again!

Hmm, I messed up indices. Let me carefully define. For CW rotation of matrix N×N: rotated[r][c] = m[N-1-c][r]. Verify with a simple case: m = [[1,0],[0,0]]. CW rotation should give [[0,1],[0,0]] (top-left moves to top-right). rotated[0][0] = m[1][0] = 0. rotated[0][1] = m[N-1-1][0] = m[1][0] = 1. So rotated[0] = [0,1]. rotated[1][0] = m[1][1] = 0; rotated[1][1] = m[0][0]=1 → rotated=[[0,1],[0,1]]. That's wrong — CW of [[1,0],[0,0]] is [[0,1],[0,0]].

Let me re-derive. Rotating 90° CW: the top row of m becomes the right column of result. Element m[r][c] goes to result[c][N-1-r]. Check: m[0][0] (top-left) → result[0][N-1-0] = result[0][1] for N=2 → top-right. ✓ CW.

So rotateCW(m): result[c][N-1-r] = m[r][c], i.e., result[r2][c2] = m[N-1-c2][r2]... let me just implement: 
```
function rotCW(m){ const N=m.length, r=[]; for(let i=0;i<N;i++){ r.push(new Array(N).fill(0)); }
 for(let y=0;y<N;y++) for(let x=0;x<N;x++) if(m[y][x]) r[x][N-1-y]=1; return r; }
```
Check I: horizontal row1: y=1, x=0..3 → r[x][N-1-1=2] → col? r[x][2] where x is col index → r[c][2] → row 2, columns 0..3 filled → horizontal row 2?? Wait r[x][N-1-y]: r's row index is x (source column), r's column index is N-1-y. So source cells (y=1, x=0..3) map to r[0..3][2] → that's row? r[row][col]: r[0][2], r[1][2], r[2][2], r[3][2] → column 2 filled at rows 0..3 → vertical bar at col 2. ✓ Good.

Rotate again (vertical col2: cells (y,2) ∀y): map → r[2][N-1-y] = r[2][3-y] → rows? r[row=2][col=3-y] for y=0..3 → cols 3,2,1,0 at row 2 → horizontal row 2. ✓ (I piece horizontal states are rows 1 and 2 — correct per SRS.)

Great. T: [[0,1,0],[1,1,1],[0,0,0]] (pointing up). rotCW: cells: (0,1),(1,0),(1,1),(1,2). Map (y,x)→(x, N-1-y): (0,1)→(1,2); (1,0)→(0,2); (1,1)→(1,2)?? wait (y=1,x=0) → r[x][N-1-y] = r[0][2]. (y=1,x=1) → r[1][2]. (y=1,x=2) → r[2][2]. (y=0,x=1) → r[1][2]. So r: row0 col2, row1 col2 (twice), row2 col2 → vertical bar col2 rows0-2 with... plus (0,1)→r[1][2]. Combined: cells {(0,2),(1,2),(2,2)} from stem? Let me list: m cells: (y=0,x=1), (y=1,x=0),(y=1,x=1),(y=1,x=2). Mapped: → (x=1, col=N-1-0=2) → r[1][2]. (1,0) → r[0][2]. (1,1) → r[1][2]. (1,2) → r[2][2]. So result cells: (0,2),(1,2),(2,2) — that's a vertical bar with... wait that's only 3 cells: (0,2),(1,2),(2,2), and (1,2) duplicated → we lost one cell! Duplicates collapse — this is the classic issue: naive coordinate mapping without accumulating properly. My loop writes r[x][N-1-y]=1 for each — duplicates fine, but 4 cells must map to 4 distinct cells. (0,1)→r[1][2]; (1,0)→r[0][2]; (1,1)→r[1][2]; (1,2)→r[2][2]. Indeed (0,1) and (1,1) both map to r[1][2] — collision! That means my mapping is wrong for rotations around matrix center with offset pieces... No wait — the mapping (y,x)→(x,N-1-y) is a valid bijection on all N² cells. (0,1) maps to (row x=1, col N-1-y=2) = (1,2). (1,1) maps to (row 1, col 2) = (1,2). Hmm both map to (1,2)? Then it's not a bijection... Let me recheck: mapping should be result[x][N-1-y] = m[y][x]. For (y=0,x=1): result[1][N-1-0 = 2] = 1 → (1,2). For (y=1,x=1): result[1][N-1-1 = 1] = 1 → (1,1) not (1,2)! I made an arithmetic slip: N-1-y for y=1 is 3-1=2... N=3: N-1=2. y=0 → col 2; y=1 → col 1. Redo: (0,1) → r[1][2]. (1,0) → r[0][2-1=1]? N-1-y = 2-1 = 1 → r[0][1]. Hmm wait (y=1,x=0) → r[x=0][N-1-y=1] → r[0][1]. (1,1) → r[1][1]. (1,2) → r[2][1]. Result cells: (1,2),(0,1),(1,1),(2,1) → that's column 1 rows 0..2 plus (1,2) → T pointing right (cells: vertical bar col1 + nub at right of middle). ✓ Correct CW rotation of T pointing up → pointing right. 

So rotCW works: `r[x][N-1-y] = m[y][x]` where I must be careful writing the loop:
```
for(let y=0;y<N;y++)for(let x=0;x<N;x++) if(m[y][x]) r[x][N-1-y]=1;
```
Here r's first index is the row = x (source column), second = N-1-y. ✓.

Precompute: SHAPES[type] = [m0, m1, m2, m3] where m0 = BASE, each next = rotCW(prev). For O (2x2), rotations identical — fine, rotation is a no-op visually; kick attempts will succeed with [0,0].

Convert matrices to cells on the fly when needed: `cellsOf(type, rot)` → iterate matrix, collect [x,y]. Cache per (type,rot) — precompute at init: `SHAPES[t][r] = cells list`.

Kick offsets: for I maybe also include up shifts; I'll use general list: [[0,0],[-1,0],[1,0],[-2,0],[2,0],[0,-1]] — with by<0 treated as collision, [0,-1] near top will fail → falls back to others. Good.

Wait — earlier I decided collide treats by<0 as collision (out of bounds) so pieces never exist above the board. Then [0,-1] kick only works if resulting cells all by>=0. Fine.

But hold on: should collide treat by<0 as blocked? If spawn y=0, some matrices have empty top rows (I: rows 0 empty... I matrix row0 empty, row1 filled; T/S/Z/L/J: row 0 has one or two cells (S: [0,1,1,...] row0 has cells; T row0 has 1 cell; J row0 1 cell; L row0 1 cell; Z row0 2 cells)). All fine at y=0.

But there's an issue: pieces at y=0 partially hidden? No, fully visible. OK.

One more consideration: rotating an S/Z/L/J/T near floor with [0,-1]... fine.

**Movement code:**

```
function tryMove(dx, dy){
  if(!piece) return false;
  if(!collides(cells(piece), piece.x+dx, piece.y+dy)){ piece.x+=dx; piece.y+=dy; return true; }
  return false;
}
```

**Locking:**
```
function lockPiece(){
  const cells = cellsOf(piece.type, piece.rot);
  for(const [cx,cy] of cells){ grid[piece.y+cy][piece.x+cx] = piece.type; }
  playLock sound;
  piece=null;
  const full=[];
  for(let r=0;r<ROWS;r++) if(grid[r].every(v=>v)) full.push(r);
  if(full.length){ clearing={rows:full, timer:CLEAR_MS, total:CLEAR_MS}; state='clearing'; sound clear; }
  else spawn();
}
```

finishClear:
```
function finishClear(){
  const n = clearing.rows.length;
  // remove rows
  const kept = grid.filter(row => !clearing.rows.includes? ... ) 
```
Careful: grid rows are arrays; use index set. `grid = grid.filter((row,i)=>!clearing.rows.includes(i)); while(grid.length<ROWS) grid.unshift(new Array(COLS).fill(0));`

Then lines += n; score += [0,100,300,500,800][n] * level; level = Math.floor(lines/10)+1; bump stats; state='playing'; spawn();

**spawn():**
```
function spawn(){
  refillBag();
  const type = bag.shift();
  piece = { type, rot:0, x: SPAWN_X[type], y:0 };
  nextType = bag[0];
  drawNext();
  gravAcc=0; lockTimer=LOCK; grounded? 
  if(collides(cells, piece.x, piece.y)){ gameOver(); }
}
```
SPAWN_X: compute per type from matrix width: Math.floor((COLS - w)/2). I: 3, O: 4, others 3 (w=3 → 3.5→3). Hmm O width 2 → (10-2)/2=4. I width 4 → 3. Fine. Compute dynamically from cells bounding box? Use BASE matrix width: BASE[type][0].length.

Also set lockTimer = 0 initially (piece in air), grounded=false; lock logic: each update: if piece exists && state playing:
```
gravAcc += dt;
const interval = downHeld ? SOFT : intervalFor(level);
while(gravAcc >= interval){
  gravAcc -= interval;
  if(tryMove(0,1)){ if(downHeld) score+=1... } 
  else { grounded handling }
}
```
Hmm: mixing gravity and soft-drop both through the same accumulator works: interval changes when downHeld. But if downHeld and interval smaller, gravity accumulator consumes multiple steps → multiple rows. Score +1 per row while soft-dropping: only when downHeld caused it. If not downHeld and gravity steps happen → no score. OK.

Grounded/lock: after each failed down move: lockActive. Implementation:

```
if(piece){
  const iv = downHeld ? SOFT_IV : gravInterval;
  gravAcc += dt;
  while(gravAcc >= iv && piece){
    gravAcc -= iv;
    if(tryMove(0,1)){
      if(downHeld){ score += 1; }  // soft drop points
      lockAcc = 0; // reset lock delay when moving down
    } else {
      lockAcc += iv;   // hmm, accumulate time grounded
      if(lockAcc >= LOCK_DELAY) lockPiece();
    }
  }
}
```
But lockAcc += iv only when step fails; while grounded, each interval tick adds iv → reaches 500ms after enough ticks. With iv=800ms at level 1, first fail adds 800 ≥ 500 → locks immediately on first grounded tick. Hmm, that makes lock delay effectively instant at slow speeds (one gravity period). Classic behavior actually locks immediately on the gravity tick when blocked. But I wanted a lock delay so players can slide. Better: track lockAcc via real dt whenever piece grounded:

```
if(piece && !canDown) { lockAcc += dt; if(lockAcc>=LOCK) lock; }
else lockAcc = 0;
```
And in the while loop: if tryMove(0,1) fails → don't add more (just stop stepping; gravity accumulator should reset to avoid burst on unground). If piece can't move down, break out of loop and clear gravAcc (set gravAcc=0) to avoid rapid catch-up after sliding. Also when grounded and player moves/rotates successfully → lockAcc = 0 (reset delay). And when grounded and downHeld → soft drop while grounded shouldn't add score. tryMove(0,1) fails when grounded so no score. Good.

Edge: after successful lateral move while grounded, lockAcc=0 → but piece may still be grounded → next frame lockAcc grows again from 0 → gets 500ms more. Nice — allows sliding. Infinite stall risk as discussed: acceptable (deliberate spam to stall is player's choice; classic games allow limited resets, but fine).

Actually wait — there's an interaction: if grounded and player keeps rotating, lockAcc resets each time — that's the classic "extendable lock". OK.

DAS lateral:
```
if(state==='playing' && piece){
  const dir = (lastDirIsLeft? -1 : 1) based on held keys;
  if(dirHeld){
    if(now >= dasRepeatAt){ tryMove(dirHeld==='L'?-1:1, 0); dasRepeatAt = now + REPEAT; }
  }
}
```
On keydown Left (not repeat): tryMove(-1,0); dasDir='L'; dasStart=now; dasRepeatAt=now+DAS. On keydown Right similar overriding. If both held, most recent wins. On keyup of the dasDir key: if other direction still held, switch: dasDir = other, dasStart/dasRepeatAt updated, immediate move. Track heldL/heldR booleans. Simplify: on keyup Left: heldL=false; if heldR { dasDir='R'; dasRepeatAt=now+DAS; tryMove(1,0);} etc.

Also vertical: down keyup → downHeld=false.

Rotation keyup not needed (act on keydown non-repeat).

Hard drop on space keydown non-repeat.

Also small extra: pressing up when state gameover shouldn't do anything; R restarts anytime.

**Prevent default:** for ArrowLeft/Right/Up/Down/Space → e.preventDefault() to stop scrolling (page likely no scroll anyway, but good practice). Also handle e.repeat for left/right: browser auto-repeat would fight DAS; I'll ignore e.repeat entirely for all keys (DAS handles repeats).

**Score display update:** function updateStats(): set textContent for score/lines/level. Call after changes. Add bump animation on clear.

**Game over:**
```
state='over'; piece=null; sound descend; 
```
Render: draw stack normally, then overlay: fillRect rgba(6,8,10,0.72) over board, then text "GAME OVER" centered (bold monospace, letter-spaced — canvas letterspacing manual? just font size 28, fillText). Below: "PRESS R TO RESTART" smaller (#8)

Also maybe show final score in overlay. Panel already shows it.

Also draw a subtle scanline? Keep clean.

**Canvas letters:** ctx.textAlign='center', font `bold 30px` monospace stack → need same font string as CSS: `'700 30px Consolas, "Cascadia Mono", "SFMono-Regular", Menlo, monospace'` — build from a JS constant matching CSS. Fine, just use `'bold 30px monospace'`? Browser picks default monospace — consistent enough. I'll define FONT stack string in JS and reuse.

**Init & restart:**

```
function reset(){
  grid = Array.from({length:ROWS},()=>Array(COLS).fill(0));
  score=0; lines=0; level=1; bag=[]; piece=null; state='playing'; clearing=null; gravAcc=0; lockAcc=0; downHeld=false; heldL=heldR=false; dasDir=null;
  spawn();
  updateStats();
}
```

**Next preview drawing:** on spawn. Canvas 100px? Let's set next canvas 96×96 CSS, dpr-scaled. Draw: clear; maybe faint border grid? Just bg transparent, panel provides bg. Compute bounding box of next cells, cell size 22, center. Draw with drawBlock(ctx2, ..., 22, ci).

Wait drawBlock uses size param s — good, parameterized.

**Bag:** 

```
function refillBag(){
  while(bag.length < 2){
    const keys = Object.keys(BASE);
    // shuffle
    for(let i=keys.length-1;i>0;i--){ const j=(Math.random()*(i+1))|0; [keys[i],keys[j]]=[keys[j],keys[i]]; }
    bag.push(...keys);
  }
}
```
Hmm this ensures bag always has ≥2 → but pushing 7 each time it dips below 2 → bag can grow beyond 7 if we only consume 1 at a time? refill when length<2 → after shift, length goes from 2 to 1 → refill pushes 7 → length 8 → next spawn length 7 → ... eventually when it dips below 2 again it adds 7. Bag length fluctuates but stays ≥2. Actually after initial: length 7 (refill pushes 7 when 0<2). spawn → 6. spawn → 5... spawn when length 2 → shift → 1 → refill → 8. Slight irregularity in distribution (bag boundary shifting) but still fine — each 7-block is shuffled. Alternative cleaner: keep `bag` and when length < 7, append a new shuffled set? That changes bag randomization semantics slightly but ensures next-piece distribution nice. Simpler standard: maintain queue; when queue length < 7 after shifting... I'll do: refill() { if(bag.length < 7) bag.push(...shuffled 7) } — then bag length always ≥ 7? After spawn: if it was 7 → 6 → refill → 7. So always 7 before spawn. Distribution: consistent 7-bag (with possible early repeats? With refill-to-7 always, it's exactly 7-bag sequence: take 1, append 7 → but appending 7 each time means the bag isn't a fixed set per 7 pieces; it's like infinite random with memory-limited... Hmm. Classic 7-bag: consume until empty then deal 7. With refill when <7: you always have ≥7 → the first 7 pieces after reset come from one shuffled set; then 8th = first of a new set interleaved... Let me trace: bag=[A..G] (7). spawn A → 6 → refill +7 → 13. spawn → 12... after 7 spawns bag=7 (from second set) then +7 → 14? No wait: refill triggers when length<7: after 7th spawn length=6 → refill +7 → 13. So the second set got merged early; you'd get pieces from two sets mixed. That's not pure 7-bag but still a valid randomizer (roughly). Honestly pure 7-bag with minimal refill threshold: `while(bag.length<7) push(shuffle7)` — same thing.

Pure approach: refill when bag empty: `if(bag.length===0) bag.push(...shuffle(7))` — then next-preview needs bag[1] which may not exist. But we only preview 1 piece (bag[0] after shifting current). After shift, bag has 6 → bag[0] exists. Only at start bag empty → refill before spawn → 7 → shift → 6, preview = bag[0] ✓. Then consume 5 more → bag length 1 → shift → 0 → refill → 7. So preview always valid. 

Let me do that: `function refill(){ if(bag.length===0) bag.push(...shuffle(KEYS)); }` called at spawn before shift. Clean pure 7-bag.

**Rendering the board each frame:**

```
function render(now){
  ctx.clearRect / fill bg;
  draw grid lines;
  draw locked cells;
  if(clearing) flash overlay rows;
  if(piece && state==='playing'){ ghost; active; }
  if(state==='over') overlay;
}
```

Ghost should also render during... only when playing. Ghost computed: gy = piece.y; while(!collides(cells, x, gy+1)) gy++. Draw cells at (x, gy) with stroke.

Grid lines: for cols 0..10 vertical lines; rows 0..20 horizontal. Use one path stroke rgba(255,255,255,0.04). Also maybe slightly stronger outer border already via CSS border.

**Crisp dpr:** 

```
function setupCanvas(cv, w, h){ const dpr = Math.min(window.devicePixelRatio||1, 2); cv.width=w*dpr; cv.height=h*dpr; cv.style.width=w+'px'; cv.style.height=h+'px'; const c=cv.getContext('2d'); c.scale(dpr,dpr); return c; }
```
Store both contexts. Note: I set style width via CSS too; inline style fine.

**Panel HTML details:**

Controls list:
- ← → — Move
- ↑ — Rotate
- ↓ — Soft drop
- Space — Hard drop
- R — Restart
- M — Sound on/off

Maybe show only gameplay-relevant plus restart/mute.

Title area: small tetromino glyph: I'll build with a 2-column grid of 4 squares arranged like an "L" or "T" using spans. E.g., T-shape: 
```
<div class="glyph"><span></span><span></span><span></span><span></span></div>
```
CSS: .glyph{display:grid; grid-template-columns:repeat(3,8px); grid-auto-rows:8px; } spans: span1 col2 row1; span2 col1 row2... simpler: give each span a grid-area via nth-child. 4 spans → T: (2,1),(1,2),(2,2),(3,2). Use inline styles or nth-child CSS. I'll do nth-child CSS.

Colors of glyph: teal accent fill.

Stat bump animation:
```
@keyframes bump { 0%{transform:scale(1)} 30%{transform:scale(1.25)} 100%{transform:scale(1)} }
.bump{ animation: bump .25s ease; }
```
JS: el.classList.remove('bump'); void el.offsetWidth; el.classList.add('bump');

Also maybe show a small "SPEED" readout? skip.

**Fonts constant:**
CSS: `font-family: "Cascadia Mono", "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;` JS mirrors: `const MONO = '"Cascadia Mono","SF Mono",Menlo,Consolas,"Liberation Mono",monospace';` used in canvas text.

**Level speed function:** `const gravInterval = () => Math.max(60, Math.round(800*Math.pow(0.82, level-1)));`

**Soft drop points:** +1 per row while soft dropping (only rows via gravity while downHeld and immediate on keydown? On keydown ArrowDown: do one immediate tryMove(0,1) if possible → score+1; and set downHeld. The loop handles subsequent steps. But careful: keydown immediate move + loop both could double-move within first frame — fine, it's just one extra row at 40ms interval; but the immediate move plus loop tick in same frame: loop's while uses accumulated time — first tick occurs after SOFT_IV ms; minor. OK.

Actually to avoid double-move weirdness, I'll skip immediate move on keydown and instead set gravAcc = SOFT_IV? Hmm: when down pressed, we want instant response. Setting downHeld=true and forcing gravAcc += SOFT_IV... Simplest: on keydown: downHeld=true; and force a step: if(tryMove(0,1)) score+=1; gravAcc=0. Slight interplay acceptable. I'll keep the immediate step.

Similarly on Left/Right keydown immediate move + set das timers.

**Also handle visibility change / tab blur**: if dt clamped to 100ms, long pauses won't cause burst (dt clamped). Good. Maybe auto-pause on blur? Not required. dt clamp handles it. But if game running and user tabs away, RAF stops anyway (browser pauses RAF) — on return, dt clamp prevents explosion. Good.

**Now write the actual code carefully.**

Let me define everything:

```js
const COLS=10, ROWS=20, CELL=28;
const CLEAR_MS=300, DAS=150, REPEAT=45, SOFT_IV=45, LOCK=500;

const BASE={
 I:[[0,0,0,0],[1,1,1,1],[0,0,0,0],[0,0,0,0]],
 O:[[1,1],[1,1]],
 T:[[0,1,0],[1,1,1],[0,0,0]],
 S:[[0,1,1],[1,1,0],[0,0,0]],
 Z:[[1,1,0],[0,1,1],[0,0,0]],
 J:[[1,0,0],[1,1,1],[0,0,0]],
 L:[[0,0,1],[1,1,1],[0,0,0]],
};
const COLORS={I:'#5fd6cf',O:'#f2c04e',T:'#b486f2',S:'#7ce08b',Z:'#f2696b',L:'#f2a15c',J:'#6fa8f2'};
```

Wait — J blue #6fa8f2 and I teal #5fd6cf distinct enough? Teal vs blue — J is more blue-violet-ish blue; I is cyan-teal. Should be distinguishable. Maybe push I more cyan: #4fd6d6? and J #5b8df0? Let me finalize:
- I: #4fd6cf teal
- O: #f2c34f amber  
- T: #b385f2 violet
- S: #7de38c green
- Z: #f2606d coral red
- L: #f2a25a orange
- J: #5f8ef0 blue

L orange #f2a25a vs O amber #f2c34f — distinguishable (orange vs yellow-amber). OK.

Precompute rotations & cells:

```js
function rotCW(m){ const N=m.length; const r=[]; for(let i=0;i<N;i++) r.push(Array(N).fill(0));
 for(let y=0;y<N;y++) for(let x=0;x<N;x++) if(m[y][x]) r[x][N-1-y]=1; return r; }

const SHAPES={};
for(const t in BASE){ let m=BASE[t]; const arr=[m]; for(let i=0;i<3;i++){ m=rotCW(m); arr.push(m);} SHAPES[t]=arr.map(matToCells); }
function matToCells(m){ const c=[]; for(let y=0;y<m.length;y++) for(let x=0;x<m.length;x++) if(m[y][x]) c.push([x,y]); return c; }
```

Note for O, all rotations same → fine.

SPAWN_X: `const SPAWN_X={}; for(t) SPAWN_X[t]=Math.floor((COLS - BASE[t][0].length)/2);` For I: (10-4)/2=3. O: 4. Others: 3. 

Hmm T spawn at x=3 occupies cols 3-5 (bar) — slightly left-of-center; visually ok. Could use Math.ceil for odd widths → 4 for 3-wide. Center columns for a 3-wide piece in 10 cols: cols 4,5,6 is more centered (10-3=7 → offsets 3 or 4). I'll use Math.ceil((COLS-w)/2) → I: 3, O: 4, T/S/Z/J/L: 4. Nice.

State variables:
```js
let grid, bag, piece, nextType, score, lines, level, state, clearing;
let gravAcc, lockAcc, downHeld, heldL, heldR, dasDir, dasAt, repAt;
```

collides:
```js
function collides(type, rot, px, py){
  const cells = SHAPES[type][rot];
  for(let i=0;i<4;i++){
    const bx=px+cells[i][0], by=py+cells[i][1];
    if(bx<0||bx>=COLS||by<0||by>=ROWS) return true;
    if(grid[by][bx]) return true;
  }
  return false;
}
```
(by<0 blocked as decided.)

tryMove(dx,dy): if piece && !collides(type,rot,x+dx,y+dy){ x+=dx; y+=dy; return true } return false.

tryRotate():
```js
function tryRotate(){
  if(!piece) return;
  const nr=(piece.rot+1)%4;
  for(const [kx,ky] of KICKS){
    if(!collides(piece.type,nr,piece.x+kx,piece.y+ky)){
      piece.rot=nr; piece.x+=kx; piece.y+=ky;
      if(grounded()) lockAcc=0;
      blip(420,.05,'square',.03);
      return;
    }
  }
}
const KICKS=[[0,0],[-1,0],[1,0],[-2,0],[2,0],[0,-1]];
```
grounded(): piece && collides(type,rot,x,y+1).

Note: [0,-1] kick with by<0-blocked: fine.

Also for O rotation: rot changes 0→1 (matrix identical) → cells same → no visual change; fine. But rot index changes, harmless.

hardDrop():
```js
function hardDrop(){
  if(!piece||state!=='playing')return;
  let d=0; while(tryMove(0,1)) d++;
  score+=2*d; updateStats();
  lockPiece(); blip(150,.09,'triangle',.05);
}
```

lockPiece():
```js
function lockPiece(){
  const cells=SHAPES[piece.type][piece.rot];
  for(const[cx,cy]of cells) grid[piece.y+cy][piece.x+cx]=piece.type;
  piece=null; lockAcc=0; gravAcc=0;
  const full=[];
  for(let r=0;r<ROWS;r++){ let c2=true; for(let c=0;c<COLS;c++) if(!grid[r][c]){c2=false;break;} if(c2) full.push(r); }
  if(full.length){
    clearing={rows:full,total:CLEAR_MS,timer:CLEAR_MS};
    state='clearing';
    // score applied at finishClear
    blip(520,.08,'square',.05); setTimeout(()=>blip(700,.10,'square',.05),90); // arpeggio
  } else { spawn(); }
}
```
Hmm setTimeout with audio after 90ms — fine.

Actually maybe apply score immediately on clear start (feels responsive in the panel) — yes! Apply score/lines/level immediately at clear detection, then animate, then finishClear only removes rows and spawns. That way panel updates instantly. Let me restructure: in lockPiece when full detected: apply clearing stats immediately:

```
const n=full.length;
lines+=n; score+=SCORES[n]*level; 
const nl=Math.floor(lines/10)+1; 
if(nl!==level){ level=nl; bump(levelEl); blip(...levelup); }
updateStats(); bump(scoreEl); bump(linesEl);
```
Then clearing anim; finishClear: remove rows, spawn, state='playing'.

Also cap: SCORES=[0,100,300,500,800].

finishClear:
```js
function finishClear(){
  const rows=new Set(clearing.rows);
  grid=grid.filter((_,i)=>!rows.has(i));
  while(grid.length<ROWS) grid.unshift(Array(COLS).fill(0));
  clearing=null; state='playing'; spawn();
}
```

spawn():
```js
function spawn(){
  if(bag.length===0){ const ks=Object.keys(BASE); ...shuffle; bag=ks; }
  const type=bag.shift();
  piece={type,rot:0,x:SPAWN_X[type],y:0};
  nextType=bag[0]; drawNext();
  gravAcc=0; lockAcc=0;
  if(collides(type,0,piece.x,0)){ piece=null; gameOver(); }
}
```

gameOver(): state='over'; blip descending: blip(400...), setTimeout blip(300), blip(200)... simple.

update(dt, now):
```js
function update(dt,now){
  if(state==='clearing'){ clearing.timer-=dt; if(clearing.timer<=0) finishClear(); return; }
  if(state!=='playing'||!piece) return;
  // DAS
  if(dasDir && now>=repAt){ if(tryMove(dasDir==='L'?-1:1,0)){} repAt=now+REPEAT; }
```
Hmm — should DAS repeat even if blocked at wall? tryMove fails; keep attempting each repeat (cheap). Also should das repeat also reset lockAcc on success while grounded → yes: if(tryMove(...)){ if(grounded()) lockAcc=0; }.

```js
  // gravity / soft drop
  const iv = downHeld ? SOFT_IV : gravIv();
  gravAcc += dt;
  let guard=0;
  while(gravAcc>=iv && guard++<20){
    gravAcc-=iv;
    if(tryMove(0,1)){
      if(downHeld){ score+=1; updateStats(); } // updateStats each row — cheap DOM write; maybe throttle: fine, it's tiny. Actually updateStats writes 3 text nodes; ok.
      lockAcc=0;
    } else {
      gravAcc=0;
      break;
    }
  }
  if(piece && grounded()){ lockAcc+=dt; if(lockAcc>=LOCK) lockPiece(); }
}
```
Wait — subtle: gravAcc=0 on grounded break: prevents accumulation burst. But then when piece slides off a ledge, gravity resumes from 0 — fine.

Also when downHeld while grounded: iv=SOFT_IV; loop tries move down, fails immediately → gravAcc=0, break. Each frame gravAcc grows by dt then reset — fine, no score while grounded. Good.

Hmm, one more: the guard<20 prevents infinite loops.

Keydown handler:
```js
document.addEventListener('keydown',e=>{
  const k=e.key;
  if(['ArrowLeft','ArrowRight','ArrowUp','ArrowDown',' '].includes(k)) e.preventDefault();
  if(e.repeat) return;
  ensureAudio();
  if(k==='m'||k==='M'){ muted=!muted; updateMuteLabel?; return; }
  if(k==='r'||k==='R'||k==='Enter'){ reset(); return; }
  if(state==='over') return;   // other keys ignored
  if(k==='ArrowLeft'){ heldL=true; dasDir='L'; dasAt=now...; if(tryMove(-1,0)&&grounded())lockAcc=0; repAt=performance.now()+DAS; }
  ...
```
Need `performance.now()` — capture `const now=performance.now()` at handler start.

ArrowRight: heldR=true; dasDir='R'; tryMove(1,0); repAt=now+DAS.
ArrowUp: tryRotate().
ArrowDown: downHeld=true; if(tryMove(0,1)){score+=1;updateStats();} gravAcc=0; lockAcc=0; — also reset lockAcc so soft drop can push into grounded? If grounded, tryMove fails; lockAcc=0 gives extra 500ms — hmm, holding down on ground shouldn't reset lock delay repeatedly... but keydown fires once (repeat ignored), so only one reset per press. Fine. Also should down while grounded force lock faster (classic: soft drop into ground locks quickly)? Not necessary; keep 500ms.

' ' (space): hardDrop().

Note: if state==='clearing', piece is null; tryMove returns false etc. Movement during clearing: keys set held flags; DAS dir set; but update() returns early during clearing... after clearing finishes, spawn happens; held flags may cause immediate das movement — das repAt already set from keydown; in update, if now>=repAt → moves. Acceptable.

But careful: during 'clearing', keydown ArrowDown sets downHeld & gravAcc stuff — harmless since piece null. On keyup reset flags regardless.

Keyup:
```js
document.addEventListener('keyup',e=>{
  const now=performance.now();
  if(e.key==='ArrowLeft'){ heldL=false; if(dasDir==='L'){ if(heldR){dasDir='R'; repAt=now+DAS; if(tryMove(1,0)&&grounded())lockAcc=0;} else dasDir=null; } }
  if(e.key==='ArrowRight'){ symmetric }
  if(e.key==='ArrowDown') downHeld=false;
});
```
Hmm — when switching dasDir to other held direction, should we also immediate-move? On keyup of L while R held: immediate move right feels natural. Included above.

Edge: keydown Right while Left held: dasDir='R', immediate move right. Standard "last pressed wins". Fine.

**updateStats / DOM:**

```js
const scoreEl=..., linesEl=..., levelEl=...;
function updateStats(){ scoreEl.textContent=score; linesEl.textContent=lines; levelEl.textContent=level; }
```
Score could be padded? e.g., String(score).padStart(6,'0') — retro nice. Score display "000000" style. Lines & level plain. I'll pad score to 6 digits.

**Render next piece:**

```js
function drawNext(){
  nctx.clearRect(0,0,NEXT_W,NEXT_H);
  if(!nextType) return;
  const cells=SHAPES[nextType][0];
  let minX=9,maxX=-1,minY=9,maxY=-1;
  for(const[cx,cy]of cells){...}
  const s=22, w=(maxX-minX+1)*s, h=(maxY-minY+1)*s;
  const ox=(NEXT_W-w)/2 - minX*s, oy=(NEXT_H-h)/2 - minY*s;
  for(const[cx,cy]of cells) drawBlock(nctx, ox+cx*s, oy+cy*s, s, nextType);
}
```
Note drawBlock's inset uses +1..s-2 relative to given size — works with s=22.

NEXT canvas size: 4*22+? I piece w=4*s=88 → canvas 104? Let me make NEXT_W=104,NEXT_H=64? Max piece height 2 cells (most) but I vertical = 4 tall → h=88. Use square 104x104? Hmm aesthetics: box width ~ panel width (panel 200 → box padding → canvas ~104). Use NEXT_W=104, NEXT_H=104? Box would be tall. Pieces are ≤2 tall except I vertical (4 tall). I could force I's rotation 0 for preview (always horizontal) → max h=2 cells → canvas 104x48ish. Preview shows next piece as it will spawn: rot 0 — that's standard (spawn orientation). So height max 2 rows → h=44-48. NEXT canvas: 104×56? Let me do 104×60 with s=24 → w max 96, h max 48 → nice. Set NEXT_W=104, NEXT_H=60. Wait: O piece 2×2=48px. Fine.

Actually simpler: make preview canvas width match panel content (~176px inner) and height 64. Cell size 24. Center horizontally. Looks good.

**drawBlock implementation (careful):**

```js
function rr(c,x,y,w,h,r){
  c.beginPath();
  c.moveTo(x+r,y);
  c.lineTo(x+w-r,y); c.quadraticCurveTo(x+w,y,x+w,y+r);
  c.lineTo(x+w,y+h-r); c.quadraticCurveTo(x+w,y+h,x+w-r,y+h);
  c.lineTo(x+r,y+h); c.quadraticCurveTo(x,y+h,x,y+h-r);
  c.lineTo(x,y+r); c.quadraticCurveTo(x,y,x+r,y);
  c.closePath();
}
function drawBlock(c,px,py,s,type){
  const col=COLORS[type];
  c.fillStyle=col; rr(c,px+1,py+1,s-2,s-2,3); c.fill();
  // bevel
  c.fillStyle='rgba(255,255,255,0.25)';
  rr(c,px+2,py+2,s-4,(s-4)*0.32,2.5); c.fill();
  c.fillStyle='rgba(0,0,0,0.28)';
  rr(c,px+2,py+2+(s-4)*0.62,s-4,(s-4)*0.32,2.5); c.fill();
  // hmm top highlight + bottom shade might leave middle band of pure color — good candy look.
  // outline
  c.strokeStyle='rgba(10,12,16,0.55)'; c.lineWidth=1;
  rr(c,px+1.5,py+1.5,s-3,s-3,2.5); c.stroke();
}
```
Hmm the bottom shade at y offset 0.62 of inner height with height 0.32 → ends at 0.94 → ok within bounds. The middle band 0.32–0.62 keeps base color. Looks like proper bevel. I think this will render nicely. Also with 28px cells: inset 1 → 26px blocks with 2px gap between (grid lines visible through 2px gaps — wait, gaps: adjacent blocks at px and px+28: first spans px+1..px+27 (s-2=26 → ends px+27), next starts px+29 → 2px gap → grid line visible in gap. Nice tiling.

But careful: bevel rects drawn with rounded corners r=2.5 on small heights — quadraticCurveTo with r bigger than h/2? h = 0.32*(s-4) = 0.32*24 = 7.68 for s=28 → r=2.5 < h/2=3.84 ✓. For s=24 (preview): inner h=20*0.32=6.4, r=2.5<3.2 ✓. OK. Actually my rr with quadratic curves handles r up to min(w,h)/2 roughly; fine.

Ghost: 
```js
function drawGhost(){
  const cells=SHAPES[piece.type][piece.rot];
  let gy=piece.y; while(!collides(piece.type,piece.rot,piece.x,gy+1)) gy++;
  if(gy===piece.y) maybe still draw (overlaps piece? ghost under piece hidden anyway).
  c.strokeStyle=COLORS[piece.type]; c.globalAlpha=0.35; c.lineWidth=1.5;
  for(const[cx,cy]of cells){ rr(c,piece.x+cx)*CELL+2.5,... size CELL-5? } draw rounded stroke inset ~3 for clear differentiation: rr(c, X+3.5, Y+3.5, CELL-7, CELL-7, 3); c.stroke();
  c.globalAlpha=1;
}
```
Hmm ghost drawn where active piece also is → double draw. Standard: skip ghost cells covered by piece? Ghost typically hidden where piece overlaps. Simpler: draw ghost only if gy>piece.y? If equal, ghost identical to piece position → drawing outline under the filled block is fine (covered). I'll just draw it; the fill covers the stroke. But stroke at inset 3.5 under block inset 1..27: stroke visible? Block spans +1..+27; ghost stroke at +3.5..+24.5 → inside block → hidden under fill? Fill drawn after ghost → covers stroke. Order: draw ghost first, then active piece. ✓.

Render locked cells:
```js
for(let r=0;r<ROWS;r++) for(let c2=0;c2<COLS;c2++){ const t=grid[r][c2]; if(t) drawBlock(ctx,c2*CELL,r*CELL,CELL,t); }
```

Clearing flash overlay:
```js
if(clearing){
  const a = clearing.timer/clearing.total; // 1→0
  ctx.fillStyle=`rgba(255,255,255,${(0.25+0.75*a).toFixed(3)})`;
  for(const r of clearing.rows) ctx.fillRect(0,r*CELL,W,CELL);
}
```
Also maybe strobe: alpha = a * (0.7+0.3*Math.sin(now*0.04))? Keep fade simple. Actually a nicer effect: two-phase — bright flash then fade. Just fade white 1→0 plus rows initially white: alpha from 0.9→0. Ok as written (0.25+0.75a: starts ~1.0, ends 0.25) then rows vanish. Good.

Also I want small particle/flash? Keep simple.

Game over overlay:
```js
if(state==='over'){
  ctx.fillStyle='rgba(8,10,14,0.78)'; ctx.fillRect(0,0,W,H);
  ctx.fillStyle='#f2606d'... title "GAME OVER" color maybe #eef; 
  ctx.textAlign='center';
  ctx.fillStyle='#f2606d'? Use red accent: draw "GAME OVER" 28px bold; then "SCORE "+score; "PRESS R TO RESTART" 12px gray.
}
```
Fonts: `ctx.font='700 30px '+MONO;`

Also small pulse: overlay alpha steady fine.

**Board canvas bg:** draw fill '#0d1117'? Let me pick: page bg #0a0c10; board bg #0f1319; panel box bg #11151c; borders #262d36. Grid lines rgba(255,255,255,0.045).

Draw grid lines:
```js
ctx.strokeStyle='rgba(255,255,255,0.05)';
ctx.beginPath();
for(let i=1;i<COLS;i++){ ctx.moveTo(i*CELL,0); ctx.lineTo(i*CELL,H); }
for(let i=1;i<ROWS;i++){ ctx.moveTo(0,i*CELL); ctx.lineTo(W,i*CELL); }
ctx.stroke();
```
With dpr scaling, 1px lines crisp-ish. lineWidth default 1. Fine. Maybe use 0.5 offsets? With dpr scale, i*CELL integer → line at exact pixel boundary → might blur across 2 px. Use lineWidth=1 and lines at .5? After ctx.scale(dpr), drawing at integer coords maps to dpr pixels; with dpr=2, a 1px line at x=28 spans pixels 56-57 → crisp. With dpr=1 (no fractional), x=28 line width 1 covers 27.5-28.5 → antialiased 2px? Canvas lineWidth 1 at x=28: covers [27.5,28.5] → two half-pixels → gray blur. To avoid, offset by 0.5: moveTo(i*CELL+0.5,...) with dpr=1 crisp. With dpr=2, +0.5 → x=56.5 canvas px → covers 56.0-57.0? hmm half-pixel again at dpr2. Perfectionism not critical: grid lines faint (alpha .05) so slight blur invisible. Keep simple: draw at i*CELL+0.5? At dpr=2 that maps to 57 → covers 56.5–57.5 → antialiased faintly. Whatever, alpha low. I'll include +0.5 in unscaled coordinates — net effect fine. Actually simpler: fillRect thin lines? Nah. Keep stroke with 0.5 offset.

Alternatively use dashed? No.

**Panel: HTML + CSS.**

Let me write full HTML now.

```html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>Blockfall</title>
<style>
  :root{
    --bg:#0a0c10; --panel:#11151c; --line:#262d36; --ink:#dfe4ea; --dim:#798391; --accent:#5fd6cf; --red:#f2606d;
    --mono:"Cascadia Mono","SF Mono",Menlo,Consolas,"Liberation Mono",monospace;
  }
  *{box-sizing:border-box;margin:0;padding:0}
  body{
    background:var(--bg); color:var(--ink); font-family:var(--mono);
    min-height:100vh; display:flex; align-items:center; justify-content:center; padding:24px;
  }
  main{ display:flex; gap:20px; align-items:flex-start; }
  .frame{ background:var(--panel); border:1px solid var(--line); border-radius:8px; padding:12px; }
  #board{ display:block; background:#0d1016; border:1px solid var(--line); border-radius:4px; }
  aside{ width:200px; display:flex; flex-direction:column; gap:12px; }
  .box{ background:var(--panel); border:1px solid var(--line); border-radius:8px; padding:12px 14px; }
  .label{ font-size:10px; letter-spacing:3px; color:var(--dim); }
  ...
</style>
```

Wait, careful about "clean, readable dark visual style" — my design: near-black bg, panel boxes with thin borders, monospace, single teal accent. Good.

Title:
```html
<div class="box head">
  <div class="brand">
    <span class="glyph" aria-hidden="true"><i></i><i></i><i></i><i></i></span>
    <h1>BLOCKFALL</h1>
  </div>
</div>
```
CSS:
```css
.head{ padding:12px 14px; }
.brand{ display:flex; align-items:center; gap:10px; }
h1{ font-size:15px; letter-spacing:4px; font-weight:700; color:var(--ink); }
.glyph{ display:grid; grid-template-columns:repeat(3,7px); grid-auto-rows:7px; gap:2px; }
.glyph i{ background:var(--accent); border-radius:1px; }
.glyph i:nth-child(1){ grid-column:2; }
.glyph i:nth-child(2){ grid-column:1; grid-row:2; }
.glyph i:nth-child(3){ grid-column:2; grid-row:2; }
.glyph i:nth-child(4){ grid-column:3; grid-row:2; }
```
That's a teal T-tetromino. Nice signature.

Next box:
```html
<section class="box">
  <span class="label">NEXT</span>
  <canvas id="next" width..></canvas>
</section>
```
Canvas centered: display block; margin:8px auto 0.

Stats box:
```html
<section class="box stats">
  <div class="stat"><span class="label">SCORE</span><span class="value" id="score">000000</span></div>
  <div class="stat"><span class="label">LINES</span><span id="lines">0</span></div>
  <div class="stat"><span class="label">LEVEL</span><span id="level">1</span></div>
</section>
```
CSS: .stat{ display:flex; justify-content:space-between; align-items:baseline; padding:4px 0; } .stat + .stat{ border-top:1px dashed #1d232c? subtle separators} maybe not needed; keep simple: margin-top 8px for subsequent. .value{ font-size:16px; font-weight:700; color:var(--ink); font-variant-numeric:tabular-nums; } score value maybe accent color? Keep neutral white, accent reserved.

Actually give SCORE value color var(--accent) to draw eye — it's the key number. Hmm, restraint: values all same white; ok.

Controls box:
```html
<section class="box keys">
  <span class="label">CONTROLS</span>
  <ul>
    <li><span><kbd>←</kbd><kbd>→</kbd></span> move</li>
    <li><span><kbd>↑</kbd></span> rotate</li>
    <li><span><kbd>↓</kbd></span> soft drop</li>
    <li><span><kbd>SPACE</kbd></span> hard drop</li>
    <li><span><kbd>R</kbd></span> restart</li>
    <li><span><kbd>M</kbd></span> sound</li>
  </ul>
</section>
```
CSS: ul{ list-style:none; margin-top:8px; } li{ display:flex; justify-content:space-between; align-items:center; font-size:11px; color:var(--dim); padding:3px 0; } kbd{ ... } gap between kbds: kbd+kbd{margin-left:4px}

kbd style:
```css
kbd{
  font-family:var(--mono); font-size:10px; color:var(--ink);
  background:#161b23; border:1px solid #333b46; border-bottom-width:2px; border-radius:4px;
  padding:2px 5px; min-width:16px; text-align:center; display:inline-block;
}
```

Footer hint box? A small status line: maybe a "SOUND: ON" indicator that M toggles — display current mute state. Add small line in controls or its own tiny box: `<section class="box status"><span class="label">SOUND</span><span id="snd">ON</span></section>`? Could combine into stats. I'll add a tiny line at bottom of keys box or separate mini box showing sound state + hint "R restarts anytime". Simpler: in the keys list, the M row label becomes "sound: on/off" dynamic? Just add small text element. I'll put a `.hint` paragraph at bottom: "M toggles sound — currently ON". Hmm overkill. I'll add a mini status box:

```html
<section class="box status">
  <div class="stat"><span class="label">SOUND</span><span class="value sm" id="sndState">ON</span></div>
  <p class="hint">Press R to restart anytime.</p>
</section>
```
hint font-size 10px color dim margin-top 8px. OK — small but useful.

Also game-over could add a red border pulse to board frame? Nice touch: on game over, add class to board canvas → border-color red-ish. `.over #board{ border-color:#f2606d }`? We can toggle class on body/main. Let me: main element gets id, add 'over' class → board border red. Also panel? Keep board only. Small detail, do it: `document.body.classList.toggle('over', state==='over')` in gameOver/reset. CSS: `body.over #board{ border-color: rgba(242,96,109,0.6); }`.

Bump animation CSS:
```css
@keyframes bump{ 0%{transform:scale(1)} 35%{transform:scale(1.28)} 100%{transform:scale(1)} }
.bump{ animation:bump .22s ease; display:inline-block; }
```
transform on inline span needs display inline-block → .value spans are inline; add display:inline-block to .value.

bump(el): el.classList.remove('bump'); void el.offsetWidth; el.classList.add('bump');

Responsive: 
```css
@media (max-width:560px){
  body{ padding:12px; }
  main{ flex-direction:column; align-items:center; }
  aside{ width:300px; }
}
```
Board 280+frame ~ 310 wide. Panel 300 matches. Fine.

Also maybe scale board down on very small screens? Canvas fixed; okay.

**Sound details:**

```js
let ac=null, muted=false;
function ensureAudio(){ if(!ac){ try{ ac=new (window.AudioContext||window.webkitAudioContext)(); }catch(e){} } if(ac&&ac.state==='suspended') ac.resume(); }
function blip(f,d,type,v){
  if(muted||!ac) return;
  try{
    const o=ac.createOscillator(), g=ac.createGain();
    o.type=type||'square'; o.frequency.value=f;
    g.gain.setValueAtTime(v||0.04, ac.currentTime);
    g.gain.exponentialRampToValueAtTime(0.0001, ac.currentTime+(d||0.08));
    o.connect(g).connect(ac.destination);
    o.start(); o.stop(ac.currentTime+(d||0.08)+0.02);
  }catch(e){}
}
```
Note: ensureAudio called on keydown; if user never presses key... game starts on load though — first gravity/lock might call blip before ac exists → muted silently (ac null → return). Actually blip checks !ac → skip. First keydown creates it. Fine. Also clicking page? Add pointerdown listener → ensureAudio. Minor. I'll also call ensureAudio on 'keydown' with any key (already) and on 'pointerdown'.

Move sound: too chatty; I'll give rotate blip(430), lock blip(160 triangle), clear arpeggio, hard drop thud blip(120,'triangle'), game over descending, level up blip(880). Soft-drop silent. DAS repeats silent. OK.

Game over sequence:
```js
function gameOverSound(){ [420,330,250,170].forEach((f,i)=>setTimeout(()=>blip(f,.14,'triangle',.05), i*130)); }
```
Level up: blip(660,.09), setTimeout blip(880,.12) 100ms.

Clear sound: n lines → pitch by count? blip(520 + 120*n)... keep arpeggio as before, maybe pitch rises with n: base 480+n*80. Fine: 
```js
const seq=[520,620,720,820].slice(0,n+? ) 
```
Simple: for tetris bigger fanfare: `[520,660,780].forEach` regardless. Keep the two-note; good.

**Now the render loop and full update. Let me also double-check the DAS repAt logic:**

On keydown Left: dasDir='L'; repAt=now+DAS; immediate tryMove(-1). In update: if(dasDir && now>=repAt){ tryMove(±1); repAt=now+REPEAT; } — note after moving once on keydown, first repeat after DAS — correct.

But dasDir also set during 'over'/'clearing'? keydown handler: after processing R/M, `if(state==='over') return;` before movement keys. But keys like ArrowLeft during 'over' would still set heldL etc. — put the over-check before. But ArrowDown keyup must always clear flag. Fine.

Also: keydown handler processes 'r'/'R'/'Enter' → reset() regardless of state (even during clearing — reset during clearing: clearing=null; state='playing'; spawn... ensure no leftover timers: finishClear never runs since clearing null; update() checks state==='clearing' false → good. But careful: reset() sets state='playing' and spawns; if old clearing timer was pending it's just an object field — reset overwrites clearing=null. OK).

Enter as restart might be surprising; keep R only? Requirement: "restart key" — R. I'll support R (and also Enter, harmless). Keep both but list R.

**Score padding:** scoreEl.textContent = String(score).padStart(6,'0'). If score > 999999 just grows naturally.

**updateStats throttling:** called on soft-drop each row — DOM writes 3 short strings per row at 45ms → negligible.

Wait, actually I realize there might be an issue with update() DAS + grounded lock reset: on successful DAS move, if grounded → lockAcc=0. Need grounded() check after move. Include.

Also on keydown immediate moves: same reset. I wrote `if(tryMove(-1,0)&&grounded())lockAcc=0;` — careful: tryMove returns true then grounded() evaluated with new position. OK. But note `grounded()` requires piece — inside tryMove success implies piece exists. Fine.

Hmm, another subtlety: `grounded()` uses collides with y+1 → piece at bottom row can't move down → true. ✓

**Ghost & hard drop loop:** hardDrop: while(tryMove(0,1)) d++; — tryMove fails when grounded → stop. ✓ Score +2d. Then lockPiece.

**One more mechanic check — spawn at y=0:**
T spawn: cells from BASE T: (1,0),(0,1),(1,1),(2,1) → at x=4 (ceil((10-3)/2)=4? (10-3)/2=3.5 ceil → 4) → cells at cols 5,4,5,6 rows 0,1. Fine, centered-ish.

I spawn x = ceil((10-4)/2) = 3 → cols 3..6 row1. ✓

O: x=4 → cols 4,5 rows 0,1. ✓

**Now clearing rows detection in lockPiece — full-width check:** `grid[r].every(v=>v!==0)` — grid values are type strings or 0 → truthy check `v` works (strings truthy, 0 falsy). Use every(v=>v). But note: type strings like 'O' truthy. ✓

**Grid init:** values 0.

**Let me also think: does downHeld soft-drop awarding points per row inflate score? Standard guideline: soft drop 1/cell. ✓**

**Level speed & display:** level from lines; speed derived. ✓ "Speed increases with level" ✓.

**Next piece on restart:** reset() clears bag → spawn draws next. Also nextType undefined initially before first spawn → drawNext guard. reset calls spawn which sets nextType.

**Preview draw colors:** drawBlock signature (c,px,py,s,type) where type used for COLORS[type] — but grid stores type strings too. Ghost uses COLORS[piece.type]. ✓ All consistent.

**Canvas sizes:** W=280,H=560. NEXT: width 168? Panel inner width: panel 200 - padding 28 = 172 → canvas 172? Hmm drawNext centers piece horizontally: NEXT_W=172, NEXT_H=64, s=24. I width 96 → centered with margins. O width 48 centered. Looks tidy.

Set canvas style via attribute width/height then dpr-scaling in JS: setupCanvas handles width/height/style and scale. For next canvas: setupCanvas(nextCv, 172, 64).

Careful: drawNext uses nctx coordinates in CSS px after scale — yes since scale applied.

**Draw order in render:**
1. bg fill (#0d1016) — canvas element already has bg via CSS, but still fillRect for cleanliness? fillRect fine.
2. grid lines.
3. locked cells.
4. clearing flash (over locked cells) — draws white over rows containing the locked cleared cells. ✓ order after cells.
5. ghost + piece (state playing).
6. game over overlay.

Also during 'clearing', no piece. ✓

**Small extra juice — landing "thud" micro-flash:** skip.

**Trailing thought on layout width:** main flex: board frame ~ 280+2 borders +24 padding = ~308 wide; panel 200; gap 20 → total ~528. Centered. Good on desktop.

**Write the final code.** Let me be careful with every function, then assemble.

Also: `const MONO='"Cascadia Mono","SF Mono",Menlo,Consolas,"Liberation Mono",monospace';` used in canvas fonts: ctx.font = '700 30px ' + MONO? Font shorthand requires valid family list; quotes inside string OK in canvas font parsing? Canvas font parsing follows CSS font shorthand; family list with quoted names should work. Safer: `ctx.font = '700 30px Consolas, Menlo, monospace';` — I'll define MONO='Consolas,Menlo,"Courier New",monospace'? Canvas parsing of quoted families works (it's CSS). I'll keep `"Cascadia Mono",Menlo,Consolas,"Courier New",monospace` unquoted where possible to reduce risk. Unquoted multi-word family names are risky ("Courier New" quoted). Use: `Menlo,Consolas,monospace` in canvas (single words, safe) — fine, canvas text is just "GAME OVER"/"PRESS R" — any monospace renders fine.

Game over overlay text:
```js
ctx.fillStyle='rgba(9,11,15,0.8)'; ctx.fillRect(0,0,W,H);
ctx.textAlign='center'; ctx.textBaseline='middle';
ctx.fillStyle='#f2606d'; ctx.font='700 34px Menlo,Consolas,monospace';
ctx.fillText('GAME OVER', W/2, H/2-38);
ctx.fillStyle='#e8edf2'; ctx.font='14px ...'; ctx.fillText('SCORE  '+score, W/2, H/2+4);
ctx.fillStyle='#798391'; ctx.font='12px ...'; ctx новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых новых

=== answer so far ===