Falling blocks / inspect each lock

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rows</div><h1>Falling blocks / inspect each lock</h1></header>
<section class="gameArea panel gameArena" id="arena" tabindex="0" aria-label="Falling block game area"><div class="scorebar"><div>Lines cleared<strong id="lines">0</strong></div><div>State<strong id="status">Paused</strong></div><div>Piece<strong id="piece">T</strong></div></div><div class="boardSplit tetrisSplit"><div id="board" class="gameBoard tetrisBoard" role="img" aria-label="20 row by 10 column block board"></div><div class="gameControls"><button id="resume" class="primary">Resume</button><button id="pause">Pause</button><button id="left">← Left</button><button id="right">Right →</button><button id="rotate">Rotate ↻</button><button id="down">Down ↓</button><button id="drop">Hard drop</button><button id="reset">Reset</button></div></div><p id="message" class="state" role="status">Paused; resume to begin.</p><p class="caption">Active ● / fixed ■. Focus game: arrows move/rotate/down; Space drops; P pauses.</p></section>
<section class="panel below"><h2>A small, explicit rule set</h2><p class="muted">Use native buttons or focus the game area for keyboard controls. Moving focus outside the game area or hiding the page pauses play. Resume starts a fresh interval; no catch-up ticks. Source is included in this file.</p><p>Seven four-cell pieces in shuffled bags. Rotation is clockwise around a fixed bounding box and anchor; O does not rotate. Invalid moves leave state intact. No wall kicks, hold, lock delay, levels or points. A blocked down-step or hard drop locks the active piece once, clears all full rows together, then spawns. Gravity is 500 ms per step.</p><div id="trace" class="record"></div><div class="sourceLinks"><a href="https://ccl.northwestern.edu/netlogo/models/Tetris">Four-cell pieces and row-clearing reference</a><a href="https://engineering.purdue.edu/OOSD/F2009/Assignments/GPA/stage2.html">Overlap, rotation and locking reference</a></div></section><details class="panel below"><summary>Manual browser checks / pending parent review</summary><table><thead><tr><th>Action</th><th>Expected observation</th></tr></thead><tbody><tr><td>Resume and press a movement key</td><td>One move per press; held-key repeats ignored.</td></tr><tr><td>Hard drop just before gravity</td><td>One lock; old gravity callback cannot move the next piece.</td></tr><tr><td>Pause / leave controls / hide page</td><td>Gravity stops and returns only on explicit Resume.</td></tr><tr><td>Reset with gravity pending</td><td>Empty fixed grid, zero lines and a fresh paused piece.</td></tr></tbody></table><p class="muted">Also inspect focus, touch controls and overflow at 360, 720 and 1440 px. Local scripted logic checks are retained separately; these browser observations remain pending.</p></details><footer class="below muted">Local working example. Edits last only while this page is open.</footer></main><script data-app>
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const shapes={I:{n:4,cells:[[1,0],[1,1],[1,2],[1,3]]},O:{n:2,cells:[[0,0],[0,1],[1,0],[1,1]]},T:{n:3,cells:[[0,1],[1,0],[1,1],[1,2]]},S:{n:3,cells:[[0,1],[0,2],[1,0],[1,1]]},Z:{n:3,cells:[[0,0],[0,1],[1,1],[1,2]]},J:{n:3,cells:[[0,0],[1,0],[1,1],[1,2]]},L:{n:3,cells:[[0,2],[1,0],[1,1],[1,2]]}};
class Blocks{constructor(queue=[],random=Math.random){this.initialQueue=[...queue];this.random=random;this.session=0;this.serial=0;this.reset()}reset(){this.session++;this.grid=Array.from({length:20},()=>Array(10).fill(0));this.lines=0;this.active=null;this.queue=[...this.initialQueue];this.status='paused';this.spawn()}next(){if(!this.queue.length){this.queue=Object.keys(shapes);for(let i=6;i>0;i--){const j=Math.floor(this.random()*(i+1));[this.queue[i],this.queue[j]]=[this.queue[j],this.queue[i]]}}return this.queue.shift()}spawn(){const type=this.next(),s=shapes[type];if(!s)throw Error('Unknown piece');const p={id:++this.serial,type,orientation:0,r:0,c:type==='O'?4:3,n:s.n,cells:s.cells.map(c=>[...c])};if(!this.valid(p)){this.active=null;this.status='over';return false}this.active=p;return true}valid(p){return p.cells.every(([r,c])=>{r+=p.r;c+=p.c;return r>=0&&r<20&&c>=0&&c<10&&!this.grid[r][c]})}move(dc){if(this.status!=='running'||!this.active)return false;const p={...this.active,c:this.active.c+dc};if(!this.valid(p))return false;this.active=p;return true}rotate(){if(this.status!=='running'||!this.active)return false;if(this.active.type==='O')return true;const p={...this.active,orientation:(this.active.orientation+1)%4,cells:this.active.cells.map(([r,c])=>[c,this.active.n-1-r])};if(!this.valid(p))return false;this.active=p;return true}down(session=this.session,id=this.active?.id){if(this.status!=='running'||session!==this.session||id!==this.active?.id)return false;const p={...this.active,r:this.active.r+1};if(this.valid(p)){this.active=p;return true}return this.lock(session,id)}hardDrop(){if(this.status!=='running'||!this.active)return false;while(this.valid({...this.active,r:this.active.r+1}))this.active.r++;return this.lock(this.session,this.active.id)}lock(session,id){if(this.status!=='running'||session!==this.session||id!==this.active?.id||!this.valid(this.active))return false;const p=this.active;this.active=null;for(const [r,c]of p.cells)this.grid[p.r+r][p.c+c]=p.type;this.compact();this.spawn();return true}compact(){const survivors=this.grid.filter(row=>!row.every(Boolean)),cleared=20-survivors.length;this.grid=[...Array.from({length:cleared},()=>Array(10).fill(0)),...survivors];this.lines+=cleared;return cleared}resume(){if(this.status==='paused')this.status='running'}pause(){if(this.status==='running')this.status='paused'}}
const game=new Blocks();let timer=null,clock=0;for(let i=0;i<200;i++){const cell=document.createElement('span');cell.className='cell';cell.setAttribute('aria-hidden','true');$('board').append(cell)}$('board').style.gridTemplateColumns='repeat(10,1fr)';function render(){const active=new Set(game.active?game.active.cells.map(([r,c])=>(r+game.active.r)+','+(c+game.active.c)):[]);[...$('board').children].forEach((cell,i)=>{const r=Math.floor(i/10),c=i%10,a=active.has(r+','+c),fixed=!!game.grid[r][c];cell.className='cell'+(a?' active':fixed?' fixed':'');cell.textContent=a?'●':fixed?'■':''});text('lines',game.lines);text('status',game.status==='over'?'Game over':game.status==='paused'?'Paused':'Running');text('piece',game.active?.type||'None');text('message',game.status==='over'?'Spawn blocked. Reset to play again.':game.status==='paused'?'Paused; resume to begin.':'Running; each active piece can lock once.');text('trace','Session '+game.session+' / active piece '+(game.active?game.active.id+' '+game.active.type+' at ['+game.active.r+','+game.active.c+'], orientation '+game.active.orientation:'none')+'\nFixed cells: '+game.grid.flat().filter(Boolean).length+'; cleared lines: '+game.lines);$('resume').disabled=game.status!=='paused';$('pause').disabled=game.status!=='running';['left','right','rotate','down','drop'].forEach(id=>$(id).disabled=game.status!=='running')}
function stop(){clock++;if(timer!==null)clearTimeout(timer);timer=null}function schedule(){stop();if(game.status!=='running')return;const token=clock,session=game.session,id=game.active?.id;timer=setTimeout(()=>{if(token!==clock||game.status!=='running')return;timer=null;game.down(session,id);render();schedule()},500)}function pause(){stop();game.pause();render()}function resume(){$('arena').focus({preventScroll:true});game.resume();render();schedule()}function act(action){if(game.status!=='running')return;const id=game.active?.id;({left:()=>game.move(-1),right:()=>game.move(1),rotate:()=>game.rotate(),down:()=>game.down(),drop:()=>game.hardDrop()})[action]();render();if(id!==game.active?.id||game.status!=='running')schedule()}
on('resume','click',resume);on('pause','click',pause);on('reset','click',()=>{stop();game.reset();render()});['left','right','rotate','down','drop'].forEach(id=>on(id,'click',()=>act(id)));on('arena','keydown',e=>{const keys={ArrowLeft:'left',ArrowRight:'right',ArrowUp:'rotate',ArrowDown:'down'};if(keys[e.key]||(e.code==='Space'&&e.target.id==='arena')){e.preventDefault();if(!e.repeat)act(keys[e.key]||'drop')}else if(e.key.toLowerCase()==='p'){e.preventDefault();if(!e.repeat)(game.status==='running'?pause:resume)()}});on('arena','focusout',e=>{if(!$('arena').contains(e.relatedTarget))pause()});document.addEventListener('visibilitychange',()=>{if(document.hidden)pause()});window.app={Blocks,shapes,game,render,resume,pause,schedule,act};render();
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