Trocando bandeiras | JavaScript e HTML: pratique lógica com desenhos, animações e um jogo

Compartilho minha solução:
<!DOCTYPE html>
<html lang="pt_BR">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">

    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            height: 100vh;
        }

        div {
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            border: 3px double brown;
            padding: 25px;
            box-shadow: 0 0 20px rgba(0, 0, 0, 0.6);
        }

        div h1,
        h3 {
            margin-bottom: 5px;
            color: brown;
        }

        canvas {
            background-color: lightgray;
        }
    </style>

    <title>Lógica de Programação II</title>
</head>

<body>
    <div>
        <h1>04 - Movendo elementos: animações simples</h1>
        <h3>09 - Trocando bandeiras</h3>

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

    </div>

    <script>

        var flagDefault = drawBrazilFlag;

        function drawBrazilFlag() {
            var canvas = document.querySelector('canvas');
            var context = canvas.getContext('2d');

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

            context.fillStyle = "yellow";
            context.beginPath();
            context.moveTo(300, 50);
            context.lineTo(50, 200);
            context.lineTo(550, 200);
            context.fill();

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

            context.fillStyle = "darkblue";
            context.beginPath();

            context.arc(300, 200, 100, 0, 2 * 3.14);
            context.fill();
        }

        function drawGermanyFlag() {
            var canvas = document.querySelector('canvas');
            var context = canvas.getContext('2d');

            context.fillStyle = 'black';
            context.fillRect(0, 0, 600, 133);

            context.fillStyle = 'red';
            context.fillRect(0, 133, 600, 133);

            context.fillStyle = 'yellow';
            context.fillRect(0, 266, 600, 133);
        }

        function swapFlag() {

            switch (flagDefault) {
                case drawBrazilFlag:
                    flagDefault = drawGermanyFlag;
                    break;
                case drawGermanyFlag:
                    flagDefault = drawBrazilFlag;
                    break;
            }

            flagDefault();
        }

        flagDefault();
        setInterval(swapFlag, 3000);

    </script>
</body>

</html>