index.co

{innerWidth:width, innerHeight:height} = @
cols = width  / 10 | 0
rows = height / 10 | 0
canvas <<<< { width, height }
ctx = canvas.getContext \2d
  &translate width, 0
  &scale -1 1
r = Math.random

write = (r! * 2 * rows | 0 for i til cols)
zero  = (r! * 2 * rows | 0 for i til cols)
chars = ('' for i til cols)

step = ->
  ctx.fillStyle = \#000
  zero :=
    for y, x of zero
      ctx.fillRect x * 10, (y - 1) * 10, 10, 10
      if r! * rows | 0
        (y + 1) % (2 * rows)
      else
        r! * 2 * rows | 0

  write :=
    for y, x of write
      # half width katakana
      c = String.fromCharCode 12448 + r! * 96
      ctx
        &fillStyle = \#0f0
        &fillText chars[x], x * 10, (y - 1) * 10
        chars[x] = c
      if r! * rows | 0
        ctx
          &fillStyle = \#000
          &fillRect x * 10, (y - 1) * 10, 10, 10
          &fillStyle = \#afa
          &fillText c, x * 10, y * 10
        (y + 1) % (2 * rows)
      else
        r! * 2 * rows | 0

setInterval step, 33