Minha bandeira do Brasil

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

<script>

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


    /*
    pincel.fillStyle = "lightgrey";
    pincel.fillRect(0, 0, 600, 400);
    */

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



    pincel.fillStyle = "yellow";//triangulo superior
    pincel.beginPath();
    pincel.moveTo(300, 50);
    pincel.lineTo(50, 200);
    pincel.lineTo(550, 200);
    pincel.fill();


    pincel.fillStyle = "yellow";//triangulo inferior
    pincel.beginPath();
    pincel.moveTo(300, 350);
    pincel.lineTo(50, 200);
    pincel.lineTo(550, 200);
    pincel.fill();

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


</script>