Sudoku constraint lab

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entries</button><button type="button" id="conflict" class="secondary">Try r9c1 = 1</button><button type="button" id="partial" class="secondary">Try r9c2 = 1</button></div></section><details><summary>Developer key · separate from entries</summary><p>The forced final row is <b class="mono">912345678</b>. Each column omits exactly one digit. A completed board must also satisfy all nine rows and all nine boxes; matching this text alone is not the completion test.</p></details><details><summary>Entry and reset rules</summary><p>Commit a blank or one digit 1–9 in an E cell. Invalid committed text is rejected as a whole and the previous accepted value is restored. G cells are immutable text. A legal digit can still conflict with a row, column, or box; the evidence appears below the board.</p><p>Reset clears the nine entries. This is a deliberately simple fixture, with no generator, difficulty rating, solver, score, or learner assessment. A fully blank puzzle would have many solutions; one solution would not prove uniqueness.</p></details><footer>Local session only · No network or saved progress. Keep maintained source records authoritative.</footer></main><script>const $=id=>document.getElementById(id);const esc=s=>String(s).replace(/[&<>"']/g,c=>({'&':'&amp;','<':'&lt;','>':'&gt;','"':'&quot;',"'":'&#39;'}[c]));

const givens=Object.freeze(('123456789/456789123/789123456/234567891/567891234/891234567/345678912/678912345').split('/').join('').split('').map(Number));let entries=Array(9).fill(''),composing=Array(9).fill(false),inputMessage='';
function boardValues(){return [...givens,...entries.map(v=>v===''?0:Number(v))]}function validate(b){const conflicts=[],invalid=[];let changed=false;for(let i=0;i<81;i++){if(i<72&&b[i]!==givens[i])changed=true;if(!Number.isInteger(b[i])||b[i]<0||b[i]>9)invalid.push(i)}const groups=[];for(let r=0;r<9;r++)groups.push({name:'Row '+(r+1),cells:Array.from({length:9},(_,c)=>r*9+c)});for(let c=0;c<9;c++)groups.push({name:'Column '+(c+1),cells:Array.from({length:9},(_,r)=>r*9+c)});for(let br=0;br<3;br++)for(let bc=0;bc<3;bc++)groups.push({name:'Box '+(br*3+bc+1),cells:Array.from({length:9},(_,i)=>(br*3+Math.floor(i/3))*9+bc*3+i%3)});for(const g of groups)for(let v=1;v<=9;v++){const cells=g.cells.filter(i=>b[i]===v);if(cells.length>1)conflicts.push({unit:g.name,value:v,cells})}const filled=b.filter(v=>Number.isInteger(v)&&v>=1&&v<=9).length;return {filled,conflicts,invalid,changed,complete:filled===81&&!invalid.length&&!conflicts.length&&!changed}}
const coordinate=i=>'r'+(Math.floor(i/9)+1)+'c'+(i%9+1);
function render(){const v=validate(boardValues());$('status').textContent=v.complete?'Complete · all constraints satisfied':v.conflicts.length?'Conflict · review the rule evidence':'Incomplete · no rule conflicts';$('progress').textContent=v.filled+' / 81 filled · '+entries.filter(Boolean).length+' / 9 editable cells filled';$('feedback').textContent=inputMessage||(v.conflicts.length?v.conflicts.map(c=>c.unit+' repeats '+c.value+' at '+c.cells.map(coordinate).join(' and ')).join('; '):v.complete?'All rows, columns, and boxes contain digits 1–9 once, with every given unchanged.':'Valid partial state. Empty cells still prevent completion.');for(let i=0;i<9;i++){const e=$('e'+i);if(!composing[i])e.value=entries[i];e.setAttribute('aria-invalid',String(v.conflicts.some(c=>c.cells.includes(72+i))))}}
function commit(i,raw){if(!/^(?:[1-9])?$/.test(raw)){inputMessage=coordinate(72+i)+': enter a blank or one digit 1–9. Rejected the full entry; previous value restored.';render();return false}entries[i]=raw;inputMessage='';render();return true}function reset(){entries=Array(9).fill('');composing=Array(9).fill(false);inputMessage='';render()}
$('board').innerHTML=Array.from({length:81},(_,i)=>i<72?'<div class="cell"><span aria-label="'+coordinate(i)+', given '+givens[i]+'"><small>G</small>'+givens[i]+'</span></div>':'<div class="cell"><label class="sr" for="e'+(i-72)+'">'+coordinate(i)+' editable, blank or one digit 1–9</label><input id="e'+(i-72)+'" inputmode="numeric" autocomplete="off" aria-label="'+coordinate(i)+' editable" aria-describedby="feedback"></div>').join('');for(let i=0;i<9;i++){const e=$('e'+i);e.addEventListener('compositionstart',()=>{composing[i]=true});e.addEventListener('compositionend',()=>{composing[i]=false;commit(i,e.value)});e.addEventListener('input',ev=>{if(!composing[i]&&!ev.isComposing)commit(i,e.value)});e.addEventListener('change',()=>{if(!composing[i])commit(i,e.value)})}$('reset').onclick=reset;$('conflict').onclick=()=>{reset();commit(0,'1');$('e0').focus()};$('partial').onclick=()=>{reset();commit(1,'1');$('e1').focus()};render();</script></body></html>