* { margin: 0; padding: 0; box-sizing: border-box; }
html, body {
    width: 100%; height: 100%;
    background: #000;
    overflow: hidden;
    display: flex; align-items: center; justify-content: center;
}
canvas {
    display: block;
    max-width: 100vw; max-height: 100vh;
    aspect-ratio: 4 / 3;
    background: #000;
}