Bandeira do Brasil

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

<script>

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

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

//triângulo da bandeira
    pincel.fillStyle='yellow';
    pincel.beginPath();
    pincel.moveTo(300, 50);
    pincel.lineTo(50, 200);
    pincel.lineTo(550, 200);
    pincel.fill();

    pincel.beginPath();
    pincel.moveTo(300, 350);
    pincel.lineTo(50, 200);
    pincel.lineTo(550, 200);
    pincel.fill();

//círculo azul da bandeira
    pincel.fillStyle = "darkblue";
    pincel.beginPath();

pincel.arc(300, 200, 100, 0, 2*3.14);
pincel.fill();
</script>