JS1k: The JavaScript code golfing competition

b=25;s=b*b;var c=document.body.children[0];c.width=c.height=s+b;x=c.getContext("2d");x.fillRect(0,0,s,s);x.fillStyle='#fff';function L(S){return S.length}a=Math;f=a.floor;function C(A){i=f(a.random()*L(A));r=A[i];A.splice(i,1);return r}function D(c,j,J,k,K){x.strokeStyle='rgb(255,'+c+','+c+')';x.beginPath();x.moveTo(j,J);x.lineTo(k,K);x.stroke();c<s&&window.setTimeout(function(){D(c+b,j,J,k,K)},b)}m={'-1':0};p=[0];while(L(p)){if(!(m[v=C(p)]||v<0||v>=s)){X=v%b;Y=f(v/b);n=X!=0?[v-1]:[v];n[1]=X!=b-1?v+1:v;n[2]=Y!=0?v-b:v;n[3]=Y!=b-1?v+b:v;m[v]=0;x.fillRect(b*X+3,b*Y+3,V=b-6,V);for(t=[0,1,2,3];L(t);){y=C(t);if(m[n[y]]){t=[];U=(y<2)?6:V;x.fillRect(b*X+3+((y==1)?V:(y==0)?-6:0),b*Y+3+((y==3)?V:(y==2)?-6:0),U,b-U)}}m[v]=1;p=p.concat(n)}}x.lineWidth=5;x.lineCap='round';d=u=v=f(b/2);X=a.min;Y=a.abs;Z=a.max;window.setInterval(function(){U=(d%2)?(d-2)*b:0;V=(d%2)?0:(d-1)*b;p=x.getImageData(Z(0,X(u,u+U)),Z(0,X(v,v+V)),Y(U)+1,Y(V)+1).data;for(i=1,m=255;i<L(p);m=X(m,p[i]),i+=4){}d=(d+1+2*!m)%4;m&&D(5,u,v,u+=U,v+=V)},b);

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

// Sizes.
b = 25;
s = b*b;

// Black out and initialize.
var c = document.body.children[0];
c.width=c.height=s+b;
x = c.getContext("2d");
x.fillRect(0,0,s,s);
x.fillStyle='#fff';

// Helpers:
// Get the length of something.
function L(S) {return S.length}
// Math.
a = Math;
// Floor.
f = a.floor;
// Pick a random element of an array, remove, and return.
function C(A) {
  i = f(a.random()*L(A));
  r = A[i];
  A.splice(i,1);
  return r;
}
// Draw a fading line.
function D(c,j,J,k,K) {
  //window.console.log('D('+c+','+sx+','+sy+','+fx+','+fy+')');
  x.strokeStyle='rgb(255,'+c+','+c+')';
  x.beginPath();
  x.moveTo(j,J);
  x.lineTo(k,K);
  x.stroke();
  c<s && window.setTimeout(function(){D(c+b,j,J,k,K);},b);
}

// Make the Maze:
m = {'-1':0};
p = [0];
while(L(p)) {
  if (!(m[v=C(p)] || v < 0 || v >= s)) {
    X = v%b;
    Y=f(v/b);
    n=X!=0?[v-1]:[v];
    n[1]=X!=b-1?v+1:v;
    n[2]=Y!=0?v-b:v;
    n[3]=Y!=b-1?v+b:v;
    m[v]=0;
    x.fillRect(b*X+3,b*Y+3,V=b-6,V);
    // Choose the side to open for the cell.  Randomly choose until we pick one
    // that opens to an explored cell.
    for(t=[0,1,2,3];L(t);){
      y=C(t);
      if(m[n[y]]) {
        t=[];
        U=(y<2)?6:V;
        x.fillRect(b*X+3+((y==1)?V:(y==0)?-6:0),
                   b*Y+3+((y==3)?V:(y==2)?-6:0),
                   U,
                   b-U);
      }
    }
    m[v]=1;
    p=p.concat(n);
  }
}

// Solve it.
x.lineWidth=5;
x.lineCap='round';
// d is direction, values are 0:up,1:right, 2:down, 3:left.
// u,v is the current position.
d=u=v=f(b/2);
X=a.min;Y=a.abs;Z=a.max;
window.setInterval(function() {
  // Get the proposed delta.
  U=(d%2)?(d-2)*b:0;
  V=(d%2)?0:(d-1)*b;
  // Check if the path is clear.
  p = x.getImageData(Z(0,X(u,u+U)),Z(0,X(v,v+V)),Y(U)+1,Y(V)+1).data;
  for(i=1,m=255;i<L(p);m=X(m,p[i]),i+=4) {}
  // Move.
  d=(d+1+2*!m)%4;
  m && D(5,u,v,u+=U,v+=V);
},b);