Bandeira

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

<script>

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

    //green rectanglo
    pincel.fillStyle = 'green';
    pincel.fillRect(0, 0, 600, 400);

    //yelow diamond
    pincel.fillStyle = 'yellow';
    pincel.beginPath();
    pincel.moveTo(300, 50);
    pincel.lineTo(50, 200);
    pincel.lineTo(300, 350);
    pincel.lineTo(550, 200);
    pincel.fill();

    //blue circle
    pincel.fillStyle = 'darkblue';
    pincel.beginPath();
    pincel.arc(300, 200, 100, 0, 2 * 3.14);
    pincel.fill();

</script>