creeper (porém partindo de (0,0))

<canvas width="600" height="400"></canvas>

<script>

    var tela = document.querySelector("canvas");
    var pincel = tela.getContext("2d");

    pincel.fillStyle = "darkgreen";
    pincel.fillRect(0, 0, 350, 300);

    pincel.fillStyle = "black";
    pincel.fillRect(50, 40, 90, 90);

    pincel.fillStyle = "black";
    pincel.fillRect(210, 40, 90, 90);

    pincel.fillStyle = "black";
    pincel.fillRect(140, 130, 70, 100);

    pincel.fillStyle = "black";
    pincel.fillRect(100, 160, 40, 110);

    pincel.fillStyle = "black";
    pincel.fillRect(210, 160, 40, 110);

</script>