.board {
  margin: 12px 0 10px; background: rgba(255,255,255,0.04);
  border: 1px solid rgba(255,255,255,0.08); border-radius: 12px; padding: 16px;
}
#equation { font-size: clamp(22px, 4vw, 30px); margin-bottom: 12px; font-weight: 800; }
.grid { display: grid; grid-template-columns: repeat(3, minmax(80px, 1fr)); gap: 10px; }
.tile { display: grid; place-items: center; height: 64px; border-radius: 10px; background: linear-gradient(180deg, rgba(147,197,253,.35), rgba(110,231,183,.25)); font-weight: 800; font-size: 20px; cursor: pointer; border: 1px solid rgba(255,255,255,0.1); }
.tile:focus { outline: 3px solid #93c5fd; }
.tile.correct { background: linear-gradient(180deg, #6ee7b7, #93c5fd); color: #0b1227; }
.tile.wrong { background: #ef4444; }
.hud { display: flex; gap: 14px; align-items: center; }
.howto { color: var(--muted); }


.howto {
  margin: 1.5rem 0;
  padding: 1rem 1.5rem;
  background-color: #f9f9f9;
  border-radius: 8px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.1);
}

.howto h2 {
  margin-top: 0;
  font-size: 1.5rem;
  color: #333;
}

.game-placeholder {
  text-align: center;
  padding: 2rem 1rem;
  color: var(--text-1);
}

.game-placeholder h3 {
  font-size: 1.5rem;
  margin: 0 0 1rem;
  color: var(--text-1);
}

.game-placeholder p {
  margin: 0.5rem 0;
  color: var(--text-2);
}

.game-placeholder .emoji {
  font-size: 3rem;
  margin: 1rem 0;
  animation: bounce 1s ease infinite;
}

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

.howto p, .howto ul {
  margin: 0.5rem 0;
  font-size: 1rem;
  color: #555;
}

.howto ul {
  list-style-type: disc;
  padding-left: 1.5rem;
}

.kbd {
  background: #eee;
  border: 1px solid #ccc;
  border-radius: 3px;
  padding: 0 4px;
  font-family: monospace;
  font-size: 0.9rem;
}