<canvas width="600" heigth="400"></canvas>
<script type="text/javascript">
    var tela = document.querySelector("canvas");
    var pincel = tela.getContext("2d");
    pincel.fillStyle = "lightblue";
    pincel.fillRect(0, 0, 600, 400);
    pincel.fillStyle = "green";
    pincel.fillRect(0, 0, 200, 400);
    pincel.fillStyle = "red";
    pincel.fillRect(400, 0, 200, 400);
    pincel.fillStyle = "yellow";
    pincel.beginPath();
    pincel.moveTo(300, 200);
    pincel.lineTo(200, 400);
    pincel.lineTo(400, 400);
    pincel.fill();
    pincel.fillStyle = "pink"
    pincel.beginPath();
    pincel.arc(300, 200, 50, 0, 2 * 3.14);
    pincel.fill();
</script>