*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Outfit", sans-serif;
  background: linear-gradient(145deg, #1a1a2e 0%, #16213e 50%, #0f3460 100%);
  color: #e8e8e8;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}

.wrapper {
  width: 100%;
  max-width: 520px;
}

/* ---------- Level selection ---------- */
.level-screen {
  text-align: center;
  padding: 2rem 1rem;
}

.level-screen h1 {
  font-size: 2.5rem;
  font-weight: 700;
  margin: 0 0 0.25rem;
  letter-spacing: 0.02em;
  background: linear-gradient(135deg, #e94560, #ff6b6b);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.level-screen p {
  margin: 0 0 2rem;
  color: #a0a0b0;
  font-size: 1rem;
}

.level-buttons {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  max-width: 220px;
  margin: 0 auto;
}

.level-btn {
  font-family: inherit;
  font-size: 1.1rem;
  font-weight: 600;
  padding: 0.9rem 1.5rem;
  border: none;
  border-radius: 12px;
  cursor: pointer;
  transition: transform 0.15s, box-shadow 0.15s;
  color: #1a1a2e;
}

.level-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.25);
}

.level-btn[data-level="easy"] {
  background: linear-gradient(135deg, #6bcb77, #4ade80);
}

.level-btn[data-level="medium"] {
  background: linear-gradient(135deg, #ffd93d, #fbbf24);
}

.level-btn[data-level="hard"] {
  background: linear-gradient(135deg, #e94560, #ef4444);
  color: #fff;
}

/* ---------- Game screen ---------- */
.game-screen.hidden,
.win-overlay.hidden,
.level-screen.hidden {
  display: none !important;
}

.game-screen {
  padding: 0.5rem 0 2rem;
}

.header {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 1.25rem;
}

.header h1 {
  font-size: 1.75rem;
  font-weight: 700;
  margin: 0;
  background: linear-gradient(135deg, #e94560, #ff6b6b);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.toolbar {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.timer {
  font-variant-numeric: tabular-nums;
  font-weight: 600;
  color: #a0a0b0;
  min-width: 3.5rem;
}

.level-badge {
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: capitalize;
  padding: 0.25rem 0.6rem;
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.1);
  color: #c0c0d0;
}

.btn {
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  padding: 0.5rem 1rem;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  background: #e94560;
  color: #fff;
  transition: background 0.2s, transform 0.1s;
}

.btn:hover {
  background: #ff6b6b;
}

.btn:active {
  transform: scale(0.98);
}

.btn-ghost {
  background: transparent;
  color: #a0a0b0;
  border: 1px solid rgba(255, 255, 255, 0.15);
}

.btn-ghost:hover {
  background: rgba(255, 255, 255, 0.08);
  color: #e8e8e8;
}

.btn-large {
  padding: 0.75rem 1.5rem;
  font-size: 1rem;
}

/* ---------- Board ---------- */
.game-container {
  position: relative;
}

.board-wrapper {
  background: rgba(255, 255, 255, 0.04);
  border-radius: 16px;
  padding: 12px;
  margin-bottom: 1rem;
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.board {
  display: grid;
  aspect-ratio: 1;
  max-width: 100%;
  margin: 0 auto;
  border: 2px solid #e94560;
  border-radius: 8px;
  overflow: hidden;
  background: #0d0d1a;
}

.board-4 { grid-template-columns: repeat(4, 1fr); grid-template-rows: repeat(4, 1fr); }
.board-6 { grid-template-columns: repeat(6, 1fr); grid-template-rows: repeat(6, 1fr); }
.board-9 { grid-template-columns: repeat(9, 1fr); grid-template-rows: repeat(9, 1fr); }

.cell {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: clamp(0.85rem, 4vw, 1.25rem);
  font-weight: 600;
  border: 1px solid rgba(255, 255, 255, 0.08);
  cursor: pointer;
  transition: background 0.15s;
  min-height: 0;
}

.cell.given {
  background: rgba(233, 69, 96, 0.12);
  color: #ff8a9e;
  cursor: default;
}

.cell.user {
  color: #e8e8e8;
}

.cell.selected {
  background: rgba(233, 69, 96, 0.35);
  outline: 2px solid #e94560;
  outline-offset: -2px;
  z-index: 1;
}

.cell.same-number {
  background: rgba(233, 69, 96, 0.2);
}

.cell.error {
  color: #ef4444;
  background: rgba(239, 68, 68, 0.15);
}

/* Box borders (set by JS: .cell-edge-r, .cell-edge-b) */
.cell.cell-edge-r {
  border-right-width: 2px;
  border-right-color: rgba(255, 255, 255, 0.2);
}

.cell.cell-edge-b {
  border-bottom-width: 2px;
  border-bottom-color: rgba(255, 255, 255, 0.2);
}

/* ---------- Number pad ---------- */
.number-pad {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 0.5rem;
}

.num-btn {
  font-family: inherit;
  font-size: 1.1rem;
  font-weight: 600;
  padding: 0.65rem;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  background: rgba(255, 255, 255, 0.08);
  color: #e8e8e8;
  border: 1px solid rgba(255, 255, 255, 0.1);
  transition: background 0.15s, transform 0.1s;
}

.num-btn:hover {
  background: rgba(255, 255, 255, 0.15);
}

.num-btn:active {
  transform: scale(0.96);
}

.num-btn-clear {
  grid-column: span 2;
  background: rgba(239, 68, 68, 0.2);
  color: #f87171;
  border-color: rgba(239, 68, 68, 0.3);
}

.num-btn-clear:hover {
  background: rgba(239, 68, 68, 0.35);
}

/* ---------- Win overlay ---------- */
.win-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.75);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 100;
  padding: 1rem;
}

.win-box {
  background: linear-gradient(145deg, #1a1a2e, #16213e);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 20px;
  padding: 2rem;
  text-align: center;
  max-width: 320px;
  width: 100%;
  box-shadow: 0 25px 50px rgba(0, 0, 0, 0.4);
}

.win-box h2 {
  margin: 0 0 0.5rem;
  font-size: 1.75rem;
  color: #e8e8e8;
}

.win-time {
  margin: 0 0 1.5rem;
  color: #a0a0b0;
  font-size: 1rem;
}

@media (min-width: 420px) {
  .board .cell {
    font-size: 1.15rem;
  }
}