* { margin: 0; padding: 0; box-sizing: border-box; }
body { overflow: hidden; background: #000; }
canvas { display: block; width: 100vw; height: 100vh; }
.buttons {
    position: fixed;
    bottom: 20px;
    left: 20px;
    display: flex;
    gap: 15px;
    z-index: 10;
}
.btn {
    color: #fff;
    text-decoration: underline;
    font-style: italic;
}