:root {
  --lvl-1: #f9df70;
  --lvl-2: #a0c35a;
  --lvl-3: #b0c4ef;
  --lvl-4: #ba81c5;
}
body {
  font-family: sans-serif;
  display: flex;
  flex-direction: column;
  align-items: center;
  background: #fff;
  color: #333;
  padding: 20px;
}
h1 {
  text-transform: uppercase;
  border-bottom: 2px solid #000;
  margin-bottom: 20px;
  letter-spacing: 2px;
}
#grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  width: 100%;
  max-width: 500px;
  margin-bottom: 20px;
}
.card {
  aspect-ratio: 1/1;
  background: #efefe6;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: bold;
  font-size: 14px;
  cursor: pointer;
  text-align: center;
  padding: 5px;
  user-select: none;
  transition: transform 0.1s;
}
.card.selected {
  background: #5a594e;
  color: white;
}
.solved {
  grid-column: span 4;
  aspect-ratio: auto;
  height: 65px;
  display: flex;
  flex-direction: column;
  border-radius: 6px;
  cursor: default;
}
.solved div {
  font-size: 13px;
  opacity: 0.9;
  margin-top: 4px;
  font-weight: normal;
}
.controls {
  display: flex;
  gap: 12px;
}
button {
  padding: 12px 24px;
  border-radius: 25px;
  border: 1px solid #000;
  background: white;
  cursor: pointer;
  font-weight: bold;
  font-size: 14px;
}
button:disabled {
  opacity: 0.3;
  cursor: not-allowed;
}
#message {
  margin-top: 20px;
  font-weight: bold;
  height: 24px;
  color: #d33;
}