bouncing marks

test.js

var mark = process.env.MARK || "-",
  window = process.env.WINDOW || 100,
  start = process.env.START || 0,
  down = true;

var canvas = "";
for(var m = 0; m < window; m++){
  canvas += " ";
}

setInterval(function(){
  if (down){
    var space = "";
    for(var j = 0; j < start; j++){
      space += " ";
    }
    console.log(space + mark);
    start++;
    if (start == window) down = false;
  } else {
    var space = "";
    for(var j = window; j > start; j--){
      space += " ";
    }
    console.log(canvas.substring(0, window - space.length) + mark);
    start--;
    if (start === 0) down = true;
  }
}, process.env.TIMEOUT || 10);