Snippet from https://play.nim-lang.org

playground.nim

import drawille, strutils, random, terminal
let
  width = terminalWidth() * 2
  height = terminalHeight() * 4
var
  c1 = newCanvas(width div 2, height div 4)
  c2 = newCanvas(width div 2, height div 4)
for x in 0 .. <(width*height div 10):
  c1.set(random(width-1), random(height-1))
while true:
  stdout.write(c1); stdout.flushFile()
  for x in 1 ..< width-1:
    for y in 1 ..< height-1:
      var alive = if c1.get(x, y): -1 else: 0
      for nx in (x - 1) .. (x + 1):
        for ny in (y - 1) .. (y + 1):
          if c1.get(nx + width, ny + height):
            inc alive
      if alive == 3 or (alive == 2 and c1.get(x, y)): c2.set(x, y)
      else: c2.unset(x, y)
  swap(c1, c2)