/* ==================== 全局样式 ==================== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --primary-color: #6366f1;
  --secondary-color: #8b5cf6;
  --success-color: #10b981;
  --error-color: #ef4444;
  --warning-color: #f59e0b;
  --bg-color: #f8fafc;
  --card-bg: #ffffff;
  --text-primary: #1e293b;
  --text-secondary: #64748b;
  --border-color: #e2e8f0;
  --border-thick: #94a3b8;
  --cell-fixed: #f1f5f9;
  --cell-selected: #dbeafe;
  --cell-highlighted: #fef3c7;
  --cell-error: #fee2e2;
  --cell-correct: #d1fae5;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 20px 25px rgba(0, 0, 0, 0.15);
  --border-radius: 12px;
  --border-radius-sm: 8px;
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 20px;
  line-height: 1.6;
}

/* ==================== 游戏容器 ==================== */
.game-container {
  background: var(--card-bg);
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-xl);
  max-width: 600px;
  width: 100%;
  padding: 30px;
  animation: fadeInUp 0.5s ease-out;
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ==================== 头部 ==================== */
.header {
  text-align: center;
  margin-bottom: 25px;
}

.title {
  font-size: 2.5rem;
  font-weight: 800;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 5px;
}

.subtitle {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

/* ==================== 信息栏 ==================== */
.info-bar {
  display: flex;
  justify-content: space-between;
  gap: 15px;
  margin-bottom: 25px;
}

.info-item {
  flex: 1;
  background: linear-gradient(135deg, #f8fafc, #f1f5f9);
  padding: 12px;
  border-radius: var(--border-radius-sm);
  text-align: center;
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--border-color);
}

.info-label {
  display: block;
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 5px;
}

.info-value {
  display: block;
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--text-primary);
}

/* ==================== 数独网格 ==================== */
.sudoku-wrapper {
  display: flex;
  justify-content: center;
  margin-bottom: 25px;
}

.sudoku-grid {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  gap: 0;
  background: var(--border-thick);
  border: 3px solid var(--border-thick);
  border-radius: var(--border-radius-sm);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
  max-width: 450px;
  width: 100%;
  aspect-ratio: 1;
}

.sudoku-cell {
  aspect-ratio: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  background: white;
  border: 1px solid var(--border-color);
  font-size: 1.5rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  position: relative;
/* Made with love by SinceraXY */
}

.sudoku-cell:hover:not(.fixed) {
  background: var(--cell-highlighted);
  transform: scale(1.05);
  z-index: 10;
}

.sudoku-cell.fixed {
  background: var(--cell-fixed);
  color: var(--text-primary);
  cursor: default;
  font-weight: 700;
}

.sudoku-cell.selected {
  background: var(--cell-selected);
  box-shadow: inset 0 0 0 3px var(--primary-color);
  z-index: 5;
}

.sudoku-cell.highlighted {
  background: var(--cell-highlighted);
}

.sudoku-cell.error {
  background: var(--cell-error);
  color: var(--error-color);
  animation: shake 0.4s ease-in-out;
}

.sudoku-cell.correct {
  background: var(--cell-correct);
  color: var(--success-color);
  animation: pulse 0.4s ease-in-out;
}

/* 3x3宫格的粗边框 */
.sudoku-cell:nth-child(3n) {
  border-right: 2px solid var(--border-thick);
}

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

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-5px); }
  75% { transform: translateX(5px); }
}

@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.1); }
}

/* ==================== 数字选择器 ==================== */
.number-pad {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 10px;
  margin-bottom: 20px;
}

.number-btn {
  aspect-ratio: 1;
  border: 2px solid var(--border-color);
  background: white;
  border-radius: var(--border-radius-sm);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
  cursor: pointer;
  transition: var(--transition);
  box-shadow: var(--shadow-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
}

.number-btn:hover {
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: white;
  border-color: var(--primary-color);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.number-btn:active {
  transform: translateY(0);
  box-shadow: var(--shadow-sm);
}

.number-btn.selected {
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: white;
  border-color: var(--primary-color);
}

.erase-btn {
  font-size: 1rem;
}

.erase-btn span:first-child {
  font-size: 1.5rem;
}

/* ==================== 控制按钮 ==================== */
.controls {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 10px;
  margin-bottom: 20px;
}

.control-btn {
  padding: 12px 20px;
  border: none;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: white;
  border-radius: var(--border-radius-sm);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  box-shadow: var(--shadow-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
}

.control-btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.control-btn:active {
  transform: translateY(0);
  box-shadow: var(--shadow-sm);
}

.control-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

.btn-icon {
  font-size: 1.2rem;
}

/* ==================== 游戏说明 ==================== */
.instructions {
  background: linear-gradient(135deg, #f8fafc, #f1f5f9);
  padding: 20px;
  border-radius: var(--border-radius-sm);
  border: 1px solid var(--border-color);
}

.instructions h3 {
  color: var(--text-primary);
  margin-bottom: 12px;
  font-size: 1.1rem;
}

.instructions ul {
  list-style: none;
  padding: 0;
}

.instructions li {
  color: var(--text-secondary);
  padding: 6px 0;
  padding-left: 25px;
  position: relative;
  font-size: 0.9rem;
}

.instructions li::before {
  content: "•";
  position: absolute;
  left: 10px;
  color: var(--primary-color);
  font-weight: bold;
/* Project: GameHub */
}

/* ==================== 模态框 ==================== */
.modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.6);
  backdrop-filter: blur(5px);
  z-index: 1000;
  justify-content: center;
  align-items: center;
  animation: fadeIn 0.3s ease-out;
}

.modal.active {
  display: flex;
}

@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

.modal-content {
  background: white;
  padding: 40px;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-xl);
  max-width: 500px;
  width: 90%;
  animation: slideUp 0.3s ease-out;
  text-align: center;
}

@keyframes slideUp {
  from {
    transform: translateY(30px);
    opacity: 0;
  }
  to {
    transform: translateY(0);
    opacity: 1;
  }
}

.modal-content h2 {
  color: var(--text-primary);
  margin-bottom: 25px;
  font-size: 1.8rem;
}

/* ==================== 难度按钮 ==================== */
.difficulty-buttons {
  display: flex;
  flex-direction: column;
  gap: 15px;
}

.difficulty-btn {
  padding: 20px;
  border: 2px solid var(--border-color);
  background: white;
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  transition: var(--transition);
  display: flex;
  align-items: center;
  gap: 15px;
  text-align: left;
}

.difficulty-btn:hover {
  border-color: var(--primary-color);
  background: linear-gradient(135deg, #f0f9ff, #e0f2fe);
  transform: translateX(5px);
  box-shadow: var(--shadow-md);
}

.difficulty-icon {
  font-size: 2.5rem;
}

.difficulty-name {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--text-primary);
  display: block;
}

.difficulty-desc {
  font-size: 0.9rem;
  color: var(--text-secondary);
  display: block;
  margin-top: 3px;
}

/* ==================== 游戏结束 ==================== */
.game-over-content {
  text-align: center;
}

.game-over-icon {
  font-size: 5rem;
  margin-bottom: 20px;
  animation: bounceIn 0.6s ease-out;
}

@keyframes bounceIn {
  0% {
    transform: scale(0);
  }
  50% {
    transform: scale(1.1);
  }
  100% {
    transform: scale(1);
  }
}

#gameOverTitle {
  color: var(--text-primary);
  margin-bottom: 25px;
}

.game-over-stats {
  display: flex;
  justify-content: center;
  gap: 40px;
  margin-bottom: 30px;
}

.stat-item {
  text-align: center;
}

.stat-label {
  display: block;
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 5px;
}

.stat-value {
  display: block;
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--primary-color);
}

.modal-btn {
  padding: 12px 40px;
  border: none;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: white;
  border-radius: var(--border-radius-sm);
  font-size: 1.1rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  box-shadow: var(--shadow-md);
}

.modal-btn:hover {

/* GitHub: https://github.com/nilgpt2024/web-game */

  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.modal-btn:active {
  transform: translateY(0);
  box-shadow: var(--shadow-sm);
}

/* ==================== 响应式设计 ==================== */
@media (max-width: 600px) {
  .game-container {
    padding: 20px;
  }

  .title {
    font-size: 2rem;
  }

  .info-bar {
    gap: 10px;
  }

  .info-item {
    padding: 10px 8px;
  }

  .info-label {
    font-size: 0.75rem;
  }

  .info-value {
    font-size: 1.1rem;
  }

  .sudoku-cell {
    font-size: 1.2rem;
  }

  .number-pad {
    gap: 8px;
  }

  .number-btn {
    font-size: 1.3rem;
  }

  .controls {
    gap: 8px;
  }

  .control-btn {
    padding: 10px 15px;
    font-size: 0.9rem;
  }

  .btn-text {
    display: none;
  }

  .btn-icon {
    font-size: 1.5rem;
  }

  .modal-content {
    padding: 30px 20px;
  }

  .game-over-stats {
    gap: 30px;
  }
}

@media (max-width: 400px) {
  .sudoku-cell {
    font-size: 1rem;
  }

  .number-btn {
    font-size: 1.1rem;
  }

  .number-pad {
    grid-template-columns: repeat(5, 1fr);
  }
}

/* ==================== 游戏消息提示 ==================== */
.game-message {
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%) scale(0.8);
  background: white;
  padding: 20px 40px;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-xl);
  font-size: 1.2rem;
  font-weight: 600;
  z-index: 2000;
  opacity: 0;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  pointer-events: none;
  text-align: center;
  min-width: 250px;
}

.game-message.show {
  opacity: 1;
  transform: translate(-50%, -50%) scale(1);
}

.game-message.success {
  background: linear-gradient(135deg, #d1fae5, #a7f3d0);
  color: #065f46;
  border: 2px solid #10b981;
}

.game-message.error {
  background: linear-gradient(135deg, #fee2e2, #fecaca);
  color: #991b1b;
  border: 2px solid #ef4444;
}

.game-message.info {
  background: linear-gradient(135deg, #dbeafe, #bfdbfe);
  color: #1e40af;
  border: 2px solid #3b82f6;
}