(function() {

  function arr(w,h) { var i, r = new Array(w); for (i=0; i<w; i++) r[i] = new Array(h); return r; }
  function random(l) { return Math.floor(Math.random() * l); }

  var screen = arr(40, 80),
      screen_x = 0,
      screen_y = 0;

  var i, j;

  for (i=0; i<40; i++) {
    for (j=0; j<80; j++) {
      screen[i][j] = ' ';
    }
  }

  function cprintf(str) { var i; for (i=0; i<str.length; i++) {
    screen[screen_y][screen_x] = str.charAt(i);
    if (++screen_x >= 80) { screen_x = 0; ++screen_y; }
    }
    return true; }
  function screen_flush() {
    var i;
    for (i=0; i<20; i++) {
      console.log(screen[i].join(''));
    }
  }
  function gotoxy(x,y) { screen_x=x; screen_y=y; }

const size = 20;
const fullfill = 100; // in %
const wallshort= 50;  // in %

var m = arr(size+1, size+1), r = arr(2,size/2*size/2), h;

function initrandom () {
 var y, x, j = 0;
 for (y = 2; y < size; y += 2)
  for (x = 2; x < size; x += 2) {
      r[0][j] = x;
      r[1][j] = y;
      j++;
     }
 h = j - 1;
}
function getrandom(p) {
 var i = random (h);
 p.x = r[0][i];
 p.y = r[1][i];
 r[0][i] = r[0][h];
 r[1][i] = r[1][h];
 return h--;
}
function view() {
 var x, y;
 for (y=0; y<=size; y++)
  for (x=0; x<=size; x++) {
    gotoxy (x*2+1,y+1);
    if (m[y][x]==0) cprintf (".");
    if (m[y][x]==1) cprintf ("_");
  }

 screen_flush();
}

function main() {


  var c, i;
  for (c = 0; c < size*size; c++) m[c] = 0;

  // Make border

  for (i = 0; i <= size; i++) {
       m[0][i] = 1;
       m[size][i] = 1;
       m[i][0] = 1;
       m[i][size] = 1;
  }

  // view ();
  initrandom();
  var startx, starty, start = {}, sx, sy;

  while (getrandom (start)) {
   startx = start.x, starty = start.y;
   if (m[starty][startx]==1) continue;
   if (random (100) > fullfill) continue;

   sx=0,sy=0;

   do {
     sx=random (3)-1;
     sy=random (3)-1;
   } while (sx==0 && sy==0 || sx!=0 && sy!=0); //sx==0 and sy==0

   while (m[starty][startx]==0) {
    if (random (100) > wallshort) {
      m[starty][startx] = 1;
      break;
    }

    m[starty][startx] = 1;

    startx+=sx;
    starty+=sy;

    m[starty][startx] = 1;

    startx +=sx;
    starty+=sy;
   }

  }

  view();
/* */
  return 0;

}

  main();

})()