.game { height: 100vh; min-height: 100%; }

@supports (height: 100dvh) {
  .game { height: 100dvh; }
}

@supports not (color: color-mix(in srgb, #fff, #000)) {
  .ball {
    background: radial-gradient(circle at 29% 21%, #fff9 0 7%, transparent 8%), var(--ball);
  }
}