*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --cell-size: 38px;
  --black: #1a1a2e;
  --white: #ffffff;
  --bg: #f0f0f5;
  --primary: #2c3e7b;
  --primary-light: #4a5fa0;
  --accent: #e8c547;
  --highlight: #d4e4ff;
  --highlight-same: #e8edff;
  --correct: #c8e6c9;
  --error: #ffcdd2;
  --revealed: #fff3cd;
  --border: #555;
  --grid-bg: #333;
  --font: 'Segoe UI', system-ui, -apple-system, sans-serif;
}

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--black);
  min-height: 100vh;
  display: flex;
  justify-content: center;
}

#app {
  width: 100%;
  max-width: 620px;
  padding: 16px;
}

header {
  text-align: center;
  margin-bottom: 12px;
}

header h1 {
  font-size: 1.6rem;
  color: var(--primary);
  font-weight: 700;
}

.date {
  color: var(--primary-light);
  font-size: 1rem;
  font-weight: 500;
}

/* Loading */
#loading {
  text-align: center;
  padding: 60px 0;
  font-size: 1.1rem;
  color: #666;
}

.hidden {
  display: none !important;
}

/* Toolbar */
.toolbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 10px;
  flex-wrap: wrap;
  gap: 8px;
}

.timer {
  display: flex;
  align-items: center;
  gap: 6px;
}

#timer-display {
  font-family: 'Courier New', monospace;
  font-size: 1.1rem;
  font-weight: 700;
  min-width: 52px;
}

.toolbar button {
  padding: 5px 12px;
  border: 1px solid #ccc;
  border-radius: 4px;
  background: var(--white);
  cursor: pointer;
  font-size: 0.85rem;
  font-family: var(--font);
  transition: background 0.15s;
}

.toolbar button:hover {
  background: #e8e8e8;
}

.actions {
  display: flex;
  gap: 6px;
}

/* Grid */
#grid-wrapper {
  display: flex;
  justify-content: center;
  margin-bottom: 12px;
  overflow-x: auto;
}

#grid {
  display: inline-grid;
  grid-template-columns: repeat(13, var(--cell-size));
  grid-template-rows: repeat(13, var(--cell-size));
  gap: 1px;
  background: var(--grid-bg);
  border: 2px solid var(--grid-bg);
  user-select: none;
}

.cell {
  position: relative;
  width: var(--cell-size);
  height: var(--cell-size);
  background: var(--white);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 1.1rem;
  font-weight: 700;
  text-transform: uppercase;
}

.cell.black {
  background: var(--black);
  cursor: default;
}

.cell .code-number {
  position: absolute;
  top: 1px;
  left: 2px;
  font-size: 0.55rem;
  font-weight: 600;
  color: #666;
  line-height: 1;
}

.cell .letter {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--black);
  margin-top: 4px;
}

.cell.selected {
  background: var(--highlight);
  outline: 2px solid var(--primary);
  outline-offset: -2px;
  z-index: 1;
}

.cell.same-code {
  background: var(--highlight-same);
}

.cell.revealed .letter {
  color: var(--primary);
}

.cell.revealed {
  background: var(--revealed);
}

.cell.correct-check {
  background: var(--correct);
}

.cell.error-check {
  background: var(--error);
}

/* Letter strip */
#letter-strip {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 3px;
  margin-bottom: 12px;
}

.strip-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  width: 28px;
  cursor: pointer;
  border-radius: 3px;
  transition: background 0.15s;
}

.strip-item:hover {
  background: #e0e0e0;
}

.strip-item.active {
  background: var(--highlight);
}

.strip-item.used {
  opacity: 0.5;
}

.strip-letter {
  font-size: 0.85rem;
  font-weight: 700;
  line-height: 1.4;
}

.strip-number {
  font-size: 0.65rem;
  color: #888;
  line-height: 1.2;
}

/* Message */
#message {
  text-align: center;
  padding: 10px 16px;
  border-radius: 6px;
  margin-bottom: 10px;
  font-weight: 600;
  font-size: 0.95rem;
}

#message.success {
  background: var(--correct);
  color: #2e7d32;
}

#message.error {
  background: var(--error);
  color: #c62828;
}

#message.info {
  background: #e3f2fd;
  color: #1565c0;
}

.entry-input {
  position: fixed;
  top: 0;
  left: 0;
  width: 1px;
  height: 1px;
  opacity: 0;
  border: 0;
  padding: 0;
  margin: 0;
  background: transparent;
  color: transparent;
  outline: none;
  caret-color: transparent;
  font-size: 16px;
  z-index: 20;
}

/* Responsive */
@media (max-width: 520px) {
  :root {
    --cell-size: calc((100vw - 48px) / 13);
  }

  .cell .code-number {
    font-size: 0.45rem;
  }

  .cell .letter {
    font-size: 0.85rem;
  }

  .toolbar {
    flex-direction: column;
    align-items: stretch;
  }

  .actions {
    justify-content: center;
  }

  .strip-item {
    width: 24px;
  }

  .strip-letter {
    font-size: 0.75rem;
  }
}

/* Completion animation */
@keyframes celebrate {
  0% { transform: scale(1); }
  50% { transform: scale(1.02); }
  100% { transform: scale(1); }
}

#grid.complete {
  animation: celebrate 0.5s ease-in-out;
}