.c4-board {
  background: var(--primary);
  background: linear-gradient(135deg, #3b82f6, #1e40af);
  padding: 8px;
  border-radius: var(--radius);
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: 4px;
  width: min(96vw, calc((60vh - 40px) * 7 / 6), 480px);
  box-shadow: var(--shadow);
}

@media (max-width: 480px) {
  .c4-board { padding: 6px; gap: 3px; }
}

.c4-slot {
  position: relative;
  aspect-ratio: 1;
  background: var(--bg);
  border-radius: 50%;
  cursor: pointer;
  border: none;
  padding: 0;
  transition: background 0.15s ease-out;
  overflow: hidden;
}

.c4-slot:hover:not(:disabled) {
  background: #e0f2fe;
}

.c4-slot:disabled {
  cursor: default;
}

.c4-disc {
  position: absolute;
  inset: 0;
  border-radius: 50%;
  animation: drop 0.35s cubic-bezier(0.5, 0, 0.7, 1) forwards;
  box-shadow: inset 0 -4px 0 rgba(0, 0, 0, 0.15), inset 0 4px 0 rgba(255, 255, 255, 0.3);
}

.c4-disc.no-anim {
  animation: none;
  transform: translateY(0);
}

.c4-disc.red { background: #ef4444; }
.c4-disc.yellow { background: #f59e0b; }

.c4-disc.win { outline: 3px solid #fff; outline-offset: -3px; }

@keyframes drop {
  from { transform: translateY(calc(-1 * var(--drop-distance, 100%))); }
  to { transform: translateY(0); }
}