* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang HK", sans-serif;
  background: #fce4ec;
  color: #222;
  padding: 10px;
  max-width: 420px;
  margin: 0 auto;
  text-align: center;
}
header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 15px; }
h1 { font-size: 1.6rem; }
.big-btn {
  background: #e91e63;
  color: white;
  border: none;
  border-radius: 12px;
  padding: 14px 22px;
  font-size: 1.2rem;
  min-height: 50px;
  cursor: pointer;
}
#board, #pieces {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin: 15px auto;
  max-width: 320px;
}
.slot, .piece {
  height: 100px;
  background: #fff;
  border: 3px dashed #ccc;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 3rem;
  cursor: pointer;
}
.piece { border-style: solid; background: #ffebee; }
.correct { background: #c8e6c9 !important; border-color: #4caf50; }