.connect4-board {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: 0.3rem;
  width: min(100%, 600px);
  margin: 0 auto;
  touch-action: manipulation;
  user-select: none;
}

.cell {
  aspect-ratio: 1;
  min-width: 0;
  background-color: #3182ce;
  border-radius: 50%;
  position: relative;
  cursor: pointer;
  overflow: hidden;
  padding: 0;
  transition: transform 0.1s ease;
  touch-action: manipulation;
}

.cell:hover {
  transform: scale(1.05);
}

.cell.empty::before {
  content: '';
  position: absolute;
  inset: 10%;
  border-radius: 50%;
  background-color: #2b6cb0;
}

.piece {
  position: absolute;
  top: 10%; left: 10%;
  width: 80%; height: 80%;
  border-radius: 50%;
  animation: dropPiece 0.4s cubic-bezier(0.3, 1, 0.8, 1);
}

@keyframes dropPiece {
  from { transform: translateY(-100%); opacity: 0; }
  to { transform: translateY(0); opacity: 1; }
}

.piece.red {
  background-color: #e53e3e;
  box-shadow: inset -4px -4px 8px rgba(0,0,0,0.3);
}

.piece.yellow {
  background-color: #ecc94b;
  box-shadow: inset -4px -4px 8px rgba(0,0,0,0.3);
}

.cell.highlight-column {
  background-color: #63b3ed !important;
  transform: scale(1.05);
}

.winning-pieces .piece {
  animation: pulseWin 0.8s ease-in-out infinite alternate;
}

@keyframes pulseWin {
  from { box-shadow: inset -4px -4px 8px rgba(0,0,0,0.3); }
  to { box-shadow: inset -6px -6px 12px var(--accent), 0 0 15px var(--accent); }
}