* {
  box-sizing: border-box;
}

body {
   margin: 0;
  min-height: 100vh;
  overflow-x: hidden;
  display: flex;
  justify-content: center;
  align-items: center;
  background: radial-gradient(circle at top, #1b2638, #05070b 65%);
}

.app {
  width: 100%;
  max-width: 520px;
  height: 100vh;
  display: flex;
  flex-direction: column;
  padding: 6px;
  gap: 4px;
}

h1 {
  margin: 4px 0;
  font-size: 24px;
  letter-spacing: 2px;
  color: #f0c475;
  text-align: center;
}

.top-bar {
  display: grid;
  grid-template-columns: auto auto 1fr auto;
  align-items: center;
  gap: 6px;
}

#timer {
  font-size: 14px;
  padding: 6px 10px;
  border-radius: 10px;
  border: 1px solid rgba(240,196,117,0.6);
  color: #f0c475;
  background: rgba(240,196,117,0.08);
}

.status {
  font-size: 12px;
  color: #f0c475;
  line-height: 1.2;
  text-align: center;
}

.difficulty {
  display: flex;
  justify-content: center;
  gap: 4px;
}

.difficulty button {
  padding: 6px 8px;
  font-size: 12px;
}

.difficulty button.active {
  background: #d6a857;
  color: #000;
}

.board {
  width: min(92vw, 520px);
  aspect-ratio: 1 / 1;

  display: grid;
  grid-template-columns: repeat(9, 1fr);

  border: 3px solid #d6a857;
  border-radius: 12px;

  overflow: hidden;

  margin: 6px auto;

  flex: unset;
  height: auto;
}
.cell {
  display: flex;
  align-items: center;
  justify-content: center;
  background: #0b111a;
  border: 1px solid rgba(214,168,87,0.25);
  position: relative;
}

.cell:nth-child(3n) {
  border-right: 2px solid #d6a857;
}

.cell:nth-child(9n) {
  border-right: none;
}

.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) {
  border-bottom: 2px solid #d6a857;
}

.cell.fixed {
  background: #1a1207;
}

.cell.selected {
  background: rgba(240,196,117,0.25);
}

.cell.related {
  background: rgba(240,196,117,0.08);
}

.cell.same-piece {
  background: rgba(214,168,87,0.22);
}

.cell.error {
  background: rgba(180,35,35,0.65);
}

.cell svg {
  width: 85%;
  height: 85%;
}

.notes-grid {
  width: 100%;
  height: 100%;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  padding: 2px;
}

.note-mark {
  display: flex;
  align-items: center;
  justify-content: center;
}

.note-mark svg {
  width: 75%;
  height: 75%;
}

.keypad {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  gap: 5px;
  padding: 4px 0;
}

.key {
  aspect-ratio: 1;
  border-radius: 10px;
  border: 1px solid rgba(240,196,117,0.4);
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  cursor: pointer;
}

.key svg {
  width: 80%;
  height: 80%;
}

.key.active {
  background: rgba(240,196,117,0.25);
  box-shadow: 0 0 8px rgba(240,196,117,0.45);
}

.count {
  position: absolute;
  bottom: 2px;
  right: 4px;
  font-size: 10px;
  color: #f0c475;
  opacity: 0.8;
}

.actions {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 6px;
}

button {
  border: 1px solid rgba(240,196,117,0.5);
  background: transparent;
  color: #f0c475;
  padding: 6px 8px;
  border-radius: 10px;
  cursor: pointer;
}

button:active {
  transform: scale(0.96);
}

#message {
  text-align: center;
  font-size: 14px;
  min-height: 18px;
  color: #f0c475;
}

@media (max-width: 480px) {
  h1 {
    font-size: 22px;
  }

  .top-bar {
    gap: 4px;
  }

  .difficulty button {
    padding: 5px 6px;
    font-size: 11px;
  }

  .board {
    max-height: 340px;
  }

  .keypad {
    gap: 4px;
  }

  button {
    font-size: 12px;
    padding: 6px 6px;
  }
}

.nav-links{
  text-align:center;
  margin:10px 0 14px;
}

.nav-links a{
  color:#6fb1ff;
  text-decoration:none;
  margin:0 10px;
  font-size:15px;
  font-weight:500;
}

.footer-links{
  text-align:center;
  margin-top:18px;
}

.footer-links a{
  color:#6fb1ff;
  text-decoration:none;
}