body {
  font-family: system-ui, sans-serif;
  background: #f7f7fa;
  margin: 0;
  padding: 0;
}
main {
  max-width: 1800px;
  margin: 2rem auto;
  padding: 1rem;
  background: #fff;
  border-radius: 12px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
}
#game-board {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: center;
  margin-top: 2rem;
}
.card {
  background: #e3e9ff;
  border-radius: 10px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.06);
  padding: 1.5rem 2.5rem;
  width: 140px;
  height: 90px;
  min-width: 140px;
  min-height: 90px;
  max-width: 140px;
  max-height: 90px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  user-select: none;
  font-size: 1.25rem;
  transition: background 0.2s, box-shadow 0.2s;
  box-sizing: border-box;
}
.card.selected {
  background: #b3c6ff;
  box-shadow: 0 2px 8px rgba(0,0,0,0.12);
}
.card.merged {
  background: #d4ffd4;
}
#status {
  margin-top: 2rem;
  text-align: center;
  font-weight: bold;
  color: #333;
}
#counters {
  display: flex;
  gap: 20px;
}