/* Sudoku Game Styles - Optimized Version 2.0 */
:root {
  /* 主色调 */
  --color-primary: #6A3E9C;
  --color-primary-gradient: linear-gradient(45deg, #6A3E9C, #8A5FB5);
  --color-accent-cyan: #00FFFF;
  --color-accent-red: #FF5252;

  /* 背景色 */
  --color-background: #121212;
  --color-bg-cell-selected: rgba(106, 62, 156, 0.4);
  --color-bg-cell-highlighted: rgba(0, 255, 255, 0.15);
  --color-bg-cell-related: rgba(255, 255, 255, 0.08);

  /* 文本颜色 */
  --color-text-primary: #EAEAEA;
  --color-text-secondary: #A0A0A0;
  --color-text-puzzle-given: #EAEAEA;
  --color-text-puzzle-input: #64B5F6;
  --color-text-puzzle-note: #BDBDBD;
  --color-text-error: #EF5350;
  --color-text-highlighted: #00FFFF;

  /* 边框与线条 */
  --color-border-grid-major: rgba(255, 255, 255, 0.4);
  --color-border-grid-minor: rgba(255, 255, 255, 0.15);

  /* 间距 */
  --spacing-xs: 4px;
  --spacing-s: 8px;
  --spacing-m: 16px;
  --spacing-l: 24px;
  --spacing-xl: 32px;

  /* 字体 */
  --font-weight-regular: 400;
  --font-weight-medium: 500;
  --font-weight-bold: 700;
}

/* 基础布局 */
body {
  background-color: var(--color-background);
  color: var(--color-text-primary);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  margin: 0;
  padding: var(--spacing-m);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--spacing-l);
  padding: var(--spacing-m) 0;
}

.header__brand {
  font-size: 1.5em;
  font-weight: var(--font-weight-bold);
}

.header__brand h1 {
  font-size: 1em;
  margin: 0;
  color: var(--color-text-primary);
  font-weight: var(--font-weight-bold);
}

/* Brand logo-like typography */
.header__brand h1,
.header__brand .site-title {
  font-weight: 800;
  letter-spacing: 0.8px;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: clamp(1.2rem, 2.4vw, 1.6rem);
  color: var(--color-text-primary); /* fallback for browsers without text clip */
  background: none;
  text-shadow: 0 1px 8px rgba(106, 62, 156, 0.25);
}

@supports ((-webkit-background-clip: text) or (background-clip: text)) {
  .header__brand h1,
  .header__brand .site-title {
    background: linear-gradient(45deg, #ffffff 0%, #ceb7ff 50%, #a886ff 100%);
    background-clip: text;
    -webkit-background-clip: text;
    color: transparent;
    -webkit-text-fill-color: transparent;
  }
}

/* Legacy nav brand support */
.nav__brand .brand__text,
.brand__text {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-weight: 800;
  letter-spacing: 0.8px;
  font-size: clamp(1.1rem, 2.3vw, 1.4rem);
  color: var(--color-text-primary);
}

.nav__brand .brand__text::before,
.brand__text::before {
  content: '🧩';
  display: inline-block;
  filter: drop-shadow(0 2px 6px rgba(106, 62, 156, 0.35));
  transform: translateY(1px);
}

@supports ((-webkit-background-clip: text) or (background-clip: text)) {
  .nav__brand .brand__text,
  .brand__text {
    background: linear-gradient(45deg, #ffffff 0%, #ceb7ff 50%, #a886ff 100%);
    background-clip: text;
    -webkit-background-clip: text;
    color: transparent;
    -webkit-text-fill-color: transparent;
  }
}

.header__brand h1::before,
.header__brand .site-title::before {
  content: '🧩';
  display: inline-block;
  filter: drop-shadow(0 2px 6px rgba(106, 62, 156, 0.35));
  transform: translateY(1px);
}

/* Decorative gradient underline for logo */
.header__brand h1::after,
.header__brand .site-title::after {
  content: '';
  display: block;
  margin-top: 4px;
  width: 44px;
  height: 3px;
  border-radius: 2px;
  background: linear-gradient(90deg, #a886ff, #6a3e9c, #00ffff);
  opacity: 0.85;
}

/* Subtle CTA tagline under the brand */
.header__tagline {
  margin: 4px 0 0 0;
  font-size: 0.9rem;
  line-height: 1.4;
  font-weight: 400;
  color: var(--color-text-secondary);
  opacity: 0.75;
}

.header__actions {
  display: flex;
  gap: var(--spacing-s);
}

.main {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  max-width: 1200px;
  margin: 0 auto;
  width: 100%;
  padding: 0 var(--spacing-m);
}

.main__content {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xl);
  width: 100%;
  max-width: 500px;
  align-items: center;
}

.game-board {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-m);
  width: 100%;
  max-width: 450px;
}

.game-status {
  display: flex;
  justify-content: space-between;
  align-items: center;
  width: 100%;
  margin-bottom: var(--spacing-m);
  padding: var(--spacing-s) var(--spacing-m);
  background: var(--color-primary-gradient);
  border-radius: 8px;
  font-size: 1.2em;
  color: var(--color-text-primary);
}

/* 网格样式 - 使用传统边框的清晰线条系统 */
.sudoku-grid {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  gap: 0;
  background-color: var(--color-background);
  border: 2px solid var(--color-border-grid-major);
  width: 100%;
  max-width: 400px;
  aspect-ratio: 1;
  margin: 0 auto var(--spacing-l) auto;
  padding: 0;
}

.sudoku-grid__cell {
  background-color: var(--color-background);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.3em;
  font-weight: var(--font-weight-medium);
  position: relative;
  transition: all 0.2s ease;
  cursor: pointer;
  aspect-ratio: 1;
  border-right: 1px solid var(--color-border-grid-minor);
  border-bottom: 1px solid var(--color-border-grid-minor);
}

/* 最右列的粗右边框 */
.sudoku-grid__cell:nth-child(9n) {
  border-right: 2px solid var(--color-border-grid-major);
}

/* 最底行的粗下边框 */
.sudoku-grid__cell:nth-child(n+73) {
  border-bottom: 2px solid var(--color-border-grid-major);
}

/* 3x3宫格粗线条 - 第3、6列的右边框 */
.sudoku-grid__cell:nth-child(3n):not(:nth-child(9n)) {
  border-right: 2px solid var(--color-border-grid-major);
}

/* 3x3宫格粗线条 - 第3、6行的下边框 */
.sudoku-grid__cell:nth-child(n+19):nth-child(-n+27),
.sudoku-grid__cell:nth-child(n+46):nth-child(-n+54) {
  border-bottom: 2px solid var(--color-border-grid-major);
}

/* 高亮样式 */
.sudoku-grid__cell--selected {
  background-color: var(--color-bg-cell-selected);
  position: relative;
  z-index: 3;
}

.sudoku-grid__cell--highlighted {
  background-color: var(--color-bg-cell-highlighted);
  color: var(--color-text-highlighted) !important;
  font-weight: var(--font-weight-bold);
  position: relative;
  z-index: 2;
}

.sudoku-grid__cell--related {
  background-color: var(--color-bg-cell-related);
  position: relative;
  z-index: 2;
}

/* 在高亮状态下保持边框清晰可见 */
.sudoku-grid__cell--selected,
.sudoku-grid__cell--highlighted,
.sudoku-grid__cell--related {
  border-color: var(--color-border-grid-minor);
}

/* 保持3x3宫格粗线条在高亮状态下的可见性 */
.sudoku-grid__cell--selected:nth-child(3n):not(:nth-child(9n)),
.sudoku-grid__cell--highlighted:nth-child(3n):not(:nth-child(9n)),
.sudoku-grid__cell--related:nth-child(3n):not(:nth-child(9n)) {
  border-right: 2px solid var(--color-border-grid-major);
}

/* 最右列在高亮状态下保持粗边框 */
.sudoku-grid__cell--selected:nth-child(9n),
.sudoku-grid__cell--highlighted:nth-child(9n),
.sudoku-grid__cell--related:nth-child(9n) {
  border-right: 2px solid var(--color-border-grid-major);
}

.sudoku-grid__cell--selected:nth-child(n+19):nth-child(-n+27),
.sudoku-grid__cell--selected:nth-child(n+46):nth-child(-n+54),
.sudoku-grid__cell--highlighted:nth-child(n+19):nth-child(-n+27),
.sudoku-grid__cell--highlighted:nth-child(n+46):nth-child(-n+54),
.sudoku-grid__cell--related:nth-child(n+19):nth-child(-n+27),
.sudoku-grid__cell--related:nth-child(n+46):nth-child(-n+54) {
  border-bottom: 2px solid var(--color-border-grid-major);
}

/* 最底行在高亮状态下保持粗边框 */
.sudoku-grid__cell--selected:nth-child(n+73),
.sudoku-grid__cell--highlighted:nth-child(n+73),
.sudoku-grid__cell--related:nth-child(n+73) {
  border-bottom: 2px solid var(--color-border-grid-major);
}

/* 单元格状态 */
.sudoku-grid__cell--given {
  color: var(--color-text-puzzle-given);
  font-weight: var(--font-weight-bold);
}

.sudoku-grid__cell:not(.sudoku-grid__cell--given) {
  color: var(--color-text-puzzle-input);
}

.sudoku-grid__cell--error {
  color: var(--color-text-error) !important;
  background-color: rgba(239, 83, 80, 0.1) !important;
  font-weight: 700 !important;
}

/* 笔记模式 */
.notes-grid {
  position: absolute;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1px;
  font-size: 0.35em;
  color: var(--color-text-puzzle-note);
  padding: var(--spacing-xs);
  width: 100%;
  height: 100%;
}

.notes-grid__note {
  display: flex;
  align-items: center;
  justify-content: center;
}

.controls {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-l);
  padding: var(--spacing-l);
  background: rgba(255, 255, 255, 0.04);
  border-radius: 16px;
  border: 1px solid rgba(255, 255, 255, 0.1);
  width: 100%;
  max-width: 450px;
  backdrop-filter: blur(10px);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
}

.controls__numbers {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--spacing-m);
}

@media (min-width: 480px) {
  .controls__numbers {
    grid-template-columns: repeat(5, 1fr);
    gap: var(--spacing-s);
  }
}

@media (min-width: 600px) {
  .controls__numbers {
    grid-template-columns: repeat(9, 1fr);
    gap: var(--spacing-s);
  }
}

.controls__actions {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--spacing-m);
}

@media (min-width: 480px) {
  .controls__actions {
    grid-template-columns: repeat(4, 1fr);
    gap: var(--spacing-s);
  }
}

/* 按钮样式 */
.button {
  background: rgba(255, 255, 255, 0.08);
  color: var(--color-text-primary);
  font-weight: var(--font-weight-medium);
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: 12px;
  padding: var(--spacing-s) var(--spacing-m);
  cursor: pointer;
  transition: all 0.3s ease;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-s);
  min-height: 44px;
  white-space: nowrap;
  position: relative;
  overflow: hidden;
}

.button::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--color-primary-gradient);
  opacity: 0;
  transition: opacity 0.3s ease;
  border-radius: 11px;
  z-index: 0;
}

.button > *,
.button span,
.button svg {
  position: relative;
  z-index: 2;
}

.button:hover {
  background: rgba(255, 255, 255, 0.12);
  box-shadow: 0 4px 20px rgba(106, 62, 156, 0.3);
  border-color: rgba(255, 255, 255, 0.3);
  transform: translateY(-1px);
}

.button:active {
  transform: translateY(0);
}

.button--active {
  background: transparent;
  border-color: var(--color-primary);
  color: #FFFFFF !important;
  box-shadow: 0 4px 25px rgba(106, 62, 156, 0.4);
}

.button--active::before {
  opacity: 0.3;
  background: linear-gradient(45deg, rgba(106, 62, 156, 0.8), rgba(138, 95, 181, 0.8));
}

.button--active,
.button--active > *,
.button--active span,
.button--active svg {
  position: relative;
  z-index: 10 !important;
  color: #FFFFFF !important;
  text-shadow: 0 2px 8px rgba(0, 0, 0, 1), 0 0 4px rgba(0, 0, 0, 0.8) !important;
  font-weight: var(--font-weight-bold) !important;
  background-color: transparent !important;
}

/* 添加额外的文本可见性保证 */
.button--active:after {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 90%;
  height: 70%;
  background: rgba(0, 0, 0, 0.3);
  border-radius: 8px;
  z-index: 1;
}

.button--active span,
.button--active svg {
  z-index: 11 !important;
}

/* 数字按钮特殊样式 */
.num-button {
  font-size: 1.2em;
  padding: 0;
  aspect-ratio: 1;
  background: rgba(255, 255, 255, 0.08);
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: 12px;
  color: var(--color-text-primary);
  cursor: pointer;
  transition: all 0.3s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 45px;
  font-weight: var(--font-weight-medium);
  position: relative;
  overflow: hidden;
}

.num-button::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--color-primary-gradient);
  opacity: 0;
  transition: opacity 0.3s ease;
  border-radius: 11px;
  z-index: 0;
}

.num-button,
.num-button span {
  position: relative;
  z-index: 2;
}

@media (min-width: 600px) {
  .num-button {
    min-height: 50px;
    font-size: 1.3em;
    border-radius: 14px;
  }
  
  .num-button::before {
    border-radius: 13px;
  }
}

.num-button:hover {
  background: rgba(0, 255, 255, 0.1);
  border-color: var(--color-accent-cyan);
  box-shadow: 0 4px 20px rgba(0, 255, 255, 0.15);
  transform: translateY(-2px);
}

.num-button:active {
  transform: translateY(0);
}

.num-button.button--active {
  background: transparent;
  border-color: var(--color-primary);
  color: #FFFFFF !important;
  box-shadow: 0 4px 25px rgba(106, 62, 156, 0.4);
  transform: translateY(-1px);
}

.num-button.button--active::before {
  opacity: 0.3;
  background: linear-gradient(45deg, rgba(106, 62, 156, 0.8), rgba(138, 95, 181, 0.8));
}

/* 确保激活状态下的文本可见性 */
.num-button.button--active,
.num-button.button--active > *,
.num-button.button--active span {
  position: relative;
  z-index: 10 !important;
  color: #FFFFFF !important;
  text-shadow: 0 2px 8px rgba(0, 0, 0, 1), 0 0 4px rgba(0, 0, 0, 0.8) !important;
  font-weight: var(--font-weight-bold) !important;
}

/* 移动端按钮按下反馈 */
@media (max-width: 600px) {
  .num-button.button--active {
    border-color: var(--color-primary) !important;
    background: rgba(106, 62, 156, 0.4) !important;
    box-shadow: 0 0 0 2px rgba(106, 62, 156, 0.5), 
                0 4px 12px rgba(106, 62, 156, 0.3) !important;
  }
}

/* 图标按钮 */
.icon-button svg {
  width: 20px;
  height: 20px;
}

/* 模态框样式 */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(0, 0, 0, 0.8);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 1000;
}

.modal-overlay.is-active {
  display: flex;
}

.modal {
  background-color: var(--color-background);
  border-radius: 12px;
  padding: var(--spacing-l);
  max-width: 90%;
  width: 400px;
  position: relative;
  border: 1px solid var(--color-border-grid-major);
}

.modal__title {
  font-size: 1.5em;
  font-weight: var(--font-weight-bold);
  margin-bottom: var(--spacing-m);
}

.modal__message {
  margin-bottom: var(--spacing-l);
  color: var(--color-text-secondary);
}

.modal__buttons {
  display: flex;
  justify-content: flex-end;
  gap: var(--spacing-m);
}

/* 胜利弹窗样式 */
.victory-modal {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(0, 0, 0, 0.9);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
}

.victory-modal.is-hidden {
  display: none;
}

.victory-modal__content {
  background: var(--color-background);
  padding: var(--spacing-xl);
  border-radius: 16px;
  text-align: center;
  max-width: 90%;
  width: 400px;
  border: 1px solid var(--color-border-grid-major);
}

.victory-modal__title {
  font-size: 2em;
  margin-bottom: var(--spacing-l);
  background: var(--color-primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  font-weight: var(--font-weight-bold);
}

.victory-modal__stats {
  margin-bottom: var(--spacing-xl);
}

.victory-modal__share {
  background-color: rgba(255, 255, 255, 0.05);
  padding: var(--spacing-m);
  border-radius: 8px;
  margin: var(--spacing-m) 0;
  font-family: monospace;
  white-space: pre;
}

/* 响应式调整 */
@media (max-width: 500px) {
  body {
    padding: var(--spacing-s);
  }

  .header {
    flex-direction: column;
    gap: var(--spacing-s);
    margin-bottom: var(--spacing-m);
    padding: var(--spacing-s) 0;
  }

  .sudoku-grid {
    max-width: 380px;
  }

  .sudoku-grid__cell {
    font-size: 1.2em;
  }

  .main__content {
    max-width: 100%;
    padding: 0;
    gap: var(--spacing-m);
  }

  .game-board {
    max-width: 100%;
  }

  .controls {
    max-width: 100%;
    margin: 0;
    padding: var(--spacing-m);
    gap: var(--spacing-m);
  }

  .controls__numbers {
    grid-template-columns: repeat(5, 1fr);
    gap: 8px;
    max-width: 100%;
  }

  .controls__actions {
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-m);
  }

  .num-button {
    min-height: 38px;
    font-size: 1.0em;
    border-radius: 10px;
    padding: 0;
    font-weight: 600;
    border: 2px solid rgba(255, 255, 255, 0.25);
    background: rgba(255, 255, 255, 0.1);
    transition: all 0.2s ease;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
  }

  .num-button:hover,
  .num-button:focus {
    transform: translateY(-1px);
    border-color: rgba(106, 62, 156, 0.6);
    background: rgba(106, 62, 156, 0.15);
    box-shadow: 0 4px 12px rgba(106, 62, 156, 0.2);
  }

  .num-button:active {
    transform: translateY(0);
    background: rgba(106, 62, 156, 0.25);
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.2);
  }

  .button {
    min-height: 40px;
    padding: 8px 16px;
    font-size: 0.9em;
    border-radius: 10px;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.1);
  }
}

/* 超小屏幕优化 (小于400px) */
@media (max-width: 400px) {
  .controls__numbers {
    grid-template-columns: repeat(5, 1fr);
    gap: 6px;
  }

  .num-button {
    min-height: 34px;
    font-size: 0.9em;
    border-radius: 8px;
    font-weight: 600;
  }

  .button {
    min-height: 36px;
    padding: 6px 12px;
    font-size: 0.85em;
  }

  .controls {
    padding: var(--spacing-s);
    gap: 8px;
  }

  .controls__actions {
    gap: 8px;
  }

  .sudoku-grid {
    max-width: 340px;
  }
}

/* 极小屏幕优化 (小于360px) */
@media (max-width: 360px) {
  .controls__numbers {
    grid-template-columns: repeat(5, 1fr);
    gap: 4px;
  }

  .num-button {
    min-height: 30px;
    font-size: 0.85em;
    border-radius: 6px;
    font-weight: 600;
  }

  .button {
    min-height: 32px;
    padding: 4px 10px;
    font-size: 0.8em;
  }

  .controls {
    padding: 6px;
    gap: 6px;
  }

  .controls__actions {
    gap: 6px;
  }

  .sudoku-grid {
    max-width: 320px;
  }
}

/* 触摸设备优化 */
@media (hover: none) and (pointer: coarse) {
  .num-button {
    min-height: 40px;
    font-size: 1.0em;
    border-radius: 10px;
    transition: all 0.15s ease;
    -webkit-tap-highlight-color: transparent;
  }

  .num-button:active {
    transform: scale(0.96);
    background: rgba(106, 62, 156, 0.3);
    border-color: rgba(106, 62, 156, 0.7);
  }

  .controls__numbers {
    gap: 8px;
  }

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

/* 宽屏手机/横屏优化 */
@media (max-width: 850px) and (min-width: 600px) and (max-height: 500px) {
  .controls__numbers {
    grid-template-columns: repeat(9, 1fr);
    gap: 6px;
  }
  
  .num-button {
    min-height: 36px;
    font-size: 0.9em;
  }
}

/* 中等屏幕优化 */
@media (min-width: 501px) and (max-width: 768px) {
  .sudoku-grid {
    max-width: 350px;
  }
  
  .sudoku-grid__cell {
    font-size: 1.2em;
  }
  
  .main__content {
    max-width: 400px;
  }
  
  .game-board {
    max-width: 400px;
  }
  
  .controls {
    max-width: 400px;
  }
}

/* 大屏幕优化 */
@media (min-width: 769px) {
  .sudoku-grid {
    max-width: 400px;
  }
  
  .sudoku-grid__cell {
    font-size: 1.4em;
  }
}

/* Footer内容样式 - 优化行长 */
.footer {
  margin-top: var(--spacing-xl);
  padding: var(--spacing-xl) var(--spacing-m);
  text-align: center;
}

.footer h2 {
  font-size: 2em;
  margin-bottom: var(--spacing-l);
  background: var(--color-primary-gradient);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  font-weight: var(--font-weight-bold);
}

.footer h3 {
  font-size: 1.5em;
  margin: var(--spacing-l) 0 var(--spacing-m);
  color: var(--color-text-primary);
}

/* 关键：限制文本容器的最大宽度以提升可读性 */
.footer > *:not(.footer-nav):not(.copyright) {
  max-width: 80ch; /* 使用ch单位，约等于80个字符宽度 */
  margin-left: auto;
  margin-right: auto;
  padding: 0 var(--spacing-m);
}

.footer p {
  line-height: 1.6;
  margin-bottom: var(--spacing-l);
  color: var(--color-text-secondary);
  text-align: left; /* 左对齐提高长文本可读性 */
}

.footer p.copyright {
  text-align: center !important;
}

.features ul {
  padding-left: var(--spacing-l);
  margin-bottom: var(--spacing-l);
  text-align: left;
}

.features li {
  margin-bottom: var(--spacing-m);
  line-height: 1.6;
  color: var(--color-text-secondary);
}

.features li strong {
  color: var(--color-text-primary);
}

.faq {
  text-align: left;
}

.faq dt {
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
  margin-bottom: var(--spacing-xs);
  margin-top: var(--spacing-l);
}

.faq dt:first-child {
  margin-top: 0;
}

.faq dd {
  margin-bottom: var(--spacing-m);
  margin-left: 0;
  line-height: 1.6;
  color: var(--color-text-secondary);
}

.footer-nav {
  text-align: center;
  margin: var(--spacing-xl) 0 var(--spacing-m);
}

.footer-nav a {
  color: var(--color-text-primary);
  text-decoration: none;
  padding: 0 var(--spacing-s);
}

.footer-nav a:hover {
  color: var(--color-accent-cyan);
}

.copyright {
  text-align: center !important;
  color: var(--color-text-secondary);
  font-size: 0.9em;
  margin: var(--spacing-m) auto 0 auto !important;
  width: 100% !important;
  max-width: none !important;
  clear: both;
  display: block !important;
}

/* 响应式调整footer */
@media (max-width: 768px) {
  .footer > *:not(.footer-nav):not(.copyright) {
    max-width: 90vw;
    padding: 0 var(--spacing-s);
  }
  
  .footer h2 {
    font-size: 1.5em;
  }

  .footer h3 {
    font-size: 1.3em;
  }
  
  .copyright {
    text-align: center !important;
    margin: var(--spacing-m) auto 0 auto !important;
    padding: 0 !important;
    width: 100% !important;
  }
}

/* ==========================================================================
   Evil 17 Challenge Styles
   ========================================================================== */

.button--special {
    background: linear-gradient(135deg, #8B0000, #FF4500);
    color: white;
    border: 1px solid #FFD700;
    box-shadow: 0 0 15px rgba(255, 215, 0, 0.3);
}

.button--special:hover {
    box-shadow: 0 0 25px rgba(255, 215, 0, 0.6);
    transform: translateY(-2px);
}

/* Evil 17 Container Variables */
#evil-17-container {
  --color-evil-primary: #8B0000;
  --color-evil-secondary: #FF4500;
  --color-evil-accent: #FFD700;
  --color-legendary: linear-gradient(135deg, #FFD700, #FF6B35, #8B0000);
  --color-hero-bg: linear-gradient(135deg, #0C0C0C 0%, #1A1A1A 50%, #2D1B1B 100%);
  --shadow-legendary: 0 0 30px rgba(255, 215, 0, 0.3);
  --glow-evil: 0 0 20px rgba(139, 0, 0, 0.5);
  background: var(--color-hero-bg);
  color: var(--color-text-primary);
}

/* Hero Section */
#evil-17-container .hero {
  padding: var(--spacing-xl) 0;
  min-height: 80vh;
  display: flex;
  align-items: center;
}

#evil-17-container .hero__container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-m);
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-xl);
  align-items: center;
}

#evil-17-container .hero__title {
  font-size: 3.5rem;
  font-weight: 700;
  margin-bottom: var(--spacing-m);
  background: var(--color-legendary);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  line-height: 1.2;
}

#evil-17-container .hero__subtitle {
  font-size: 1.5rem;
  color: var(--color-evil-accent);
  margin-bottom: var(--spacing-m);
  font-weight: 600;
}

#evil-17-container .hero__description {
  font-size: 1.1rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
  margin-bottom: var(--spacing-xl);
}

#evil-17-container .hero__stats {
  display: flex;
  gap: var(--spacing-xl);
}

#evil-17-container .stat {
  text-align: center;
}

#evil-17-container .stat__number {
  display: block;
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--color-evil-accent);
  margin-bottom: var(--spacing-xs);
}

#evil-17-container .stat__label {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  text-transform: uppercase;
  letter-spacing: 1px;
}

/* Legendary Grid Visual */
#evil-17-container .legendary-grid {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
}

#evil-17-container .grid-preview {
  width: 300px;
  height: 300px;
  background: rgba(0, 0, 0, 0.8);
  border: 2px solid var(--color-evil-primary);
  border-radius: 12px;
  position: relative;
  overflow: hidden;
}

#evil-17-container .grid-glow {
  position: absolute;
  top: -20px;
  left: -20px;
  right: -20px;
  bottom: -20px;
  background: var(--color-legendary);
  border-radius: 20px;
  opacity: 0.3;
  filter: blur(20px);
  animation: pulse 3s ease-in-out infinite;
  z-index: -1;
}

@keyframes pulse {
  0%, 100% { opacity: 0.3; }
  50% { opacity: 0.6; }
}

/* Arena Section */
#evil-17-container .arena {
  padding: var(--spacing-xl) 0;
  background: rgba(0, 0, 0, 0.3);
}

#evil-17-container .arena__container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-m);
}

#evil-17-container .arena__title {
  font-size: 2.5rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: var(--spacing-m);
  color: var(--color-text-primary);
}

#evil-17-container .arena__subtitle {
  text-align: center;
  font-size: 1.2rem;
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-xl);
}

#evil-17-container .puzzle-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: var(--spacing-l);
}

/* Puzzle Cards */
#evil-17-container .puzzle-card {
  background: rgba(0, 0, 0, 0.6);
  border: 1px solid var(--color-evil-primary);
  border-radius: 16px;
  padding: var(--spacing-l);
  cursor: pointer;
  transition: all 0.3s ease;
  position: relative;
  overflow: hidden;
}

#evil-17-container .puzzle-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--color-legendary);
  opacity: 0;
  transition: opacity 0.3s ease;
  z-index: -1;
}

#evil-17-container .puzzle-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-legendary);
}

#evil-17-container .puzzle-card:hover::before {
  opacity: 0.1;
}

#evil-17-container .puzzle-card__header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: var(--spacing-m);
}

#evil-17-container .puzzle-card__name {
  font-size: 1.4rem;
  font-weight: 600;
  color: var(--color-evil-accent);
  margin: 0;
}

#evil-17-container .puzzle-card__difficulty {
  background: var(--color-evil-primary);
  color: white;
  padding: var(--spacing-xs) var(--spacing-s);
  border-radius: 20px;
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
}

#evil-17-container .puzzle-card__description {
  color: var(--color-text-secondary);
  line-height: 1.6;
  margin-bottom: var(--spacing-m);
}

#evil-17-container .puzzle-card__stats {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: var(--spacing-m);
  border-top: 1px solid rgba(139, 0, 0, 0.3);
}

#evil-17-container .puzzle-card__record {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
}

#evil-17-container .puzzle-card__clues {
  font-weight: 600;
  color: var(--color-evil-accent);
}

/* Mentor Panel */
#evil-17-container .mentor-panel {
  background: rgba(0, 0, 0, 0.6);
  border: 1px solid var(--color-evil-primary);
  border-radius: 12px;
  padding: var(--spacing-l);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-m);
}

#evil-17-container .mentor-header h4 {
  margin: 0;
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--color-evil-accent);
  text-align: center;
  border-bottom: 1px solid rgba(139, 0, 0, 0.3);
  padding-bottom: var(--spacing-m);
}

#evil-17-container .mentor-content {
  color: var(--color-text-secondary);
  line-height: 1.6;
  flex-grow: 1;
}

#evil-17-container .mentor-actions {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-s);
}

/* Lore Section */
#evil-17-container .lore {
  padding: var(--spacing-xl) 0;
}

#evil-17-container .lore__container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-m);
}

#evil-17-container .lore__title {
  font-size: 2.5rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: var(--spacing-xl);
  color: var(--color-text-primary);
}

#evil-17-container .lore-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-l);
}

#evil-17-container .lore-card {
  background: rgba(0, 0, 0, 0.3);
  padding: var(--spacing-l);
  border-radius: 12px;
  border: 1px solid rgba(139, 0, 0, 0.2);
}

#evil-17-container .lore-card__icon {
  font-size: 2rem;
  margin-bottom: var(--spacing-m);
}

#evil-17-container .lore-card h3 {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--color-evil-accent);
  margin-bottom: var(--spacing-s);
}

#evil-17-container .lore-card p {
  color: var(--color-text-secondary);
  line-height: 1.6;
  font-size: 0.9rem;
}

/* Technique Library */
#evil-17-container .technique-library {
  padding: var(--spacing-xl) 0;
  background: rgba(0, 0, 0, 0.3);
}

#evil-17-container .library__container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-m);
}

#evil-17-container .library__title {
  font-size: 2.5rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: var(--spacing-m);
  color: var(--color-text-primary);
}

#evil-17-container .library__subtitle {
  text-align: center;
  font-size: 1.2rem;
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-xl);
}

#evil-17-container .technique-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-l);
}

#evil-17-container .technique-card {
  background: rgba(0, 0, 0, 0.6);
  border: 1px solid var(--color-evil-primary);
  border-radius: 12px;
  padding: var(--spacing-l);
  text-decoration: none;
  color: inherit;
  transition: all 0.3s ease;
}

#evil-17-container .technique-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-legendary);
  background: rgba(139, 0, 0, 0.2);
}

#evil-17-container .technique-icon {
  font-size: 2rem;
  margin-bottom: var(--spacing-m);
}

#evil-17-container .technique-card h3 {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--color-evil-accent);
  margin-bottom: var(--spacing-s);
}

#evil-17-container .technique-card p {
  color: var(--color-text-secondary);
  line-height: 1.6;
  font-size: 0.9rem;
}

/* Community Section */
#evil-17-container .community {
  padding: var(--spacing-xl) 0;
}

#evil-17-container .community__container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-m);
}

#evil-17-container .community__title {
  font-size: 2.5rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: var(--spacing-xl);
  color: var(--color-text-primary);
}

#evil-17-container .community-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-xl);
  align-items: flex-start;
}

#evil-17-container .leaderboard {
  background: rgba(0, 0, 0, 0.3);
  padding: var(--spacing-l);
  border-radius: 12px;
}

#evil-17-container .leaderboard h3 {
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--color-evil-accent);
  margin-bottom: var(--spacing-m);
  border-bottom: 1px solid rgba(139, 0, 0, 0.3);
  padding-bottom: var(--spacing-m);
}

#evil-17-container .community-actions {
  padding: var(--spacing-l);
}

#evil-17-container .community-actions h3 {
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--color-evil-accent);
  margin-bottom: var(--spacing-m);
}

#evil-17-container .community-actions p {
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-l);
}

#evil-17-container .community-actions .button {
  margin-right: var(--spacing-m);
  margin-bottom: var(--spacing-m);
}

/* Controls adjustments for Evil 17 */
#evil-17-container .controls {
    background-color: transparent;
    border: none;
    padding: 0;
}

#evil-17-container .controls__numbers .num-button {
    background-color: rgba(255, 255, 255, 0.1);
    border: 1px solid var(--color-evil-primary);
    color: var(--color-text-primary);
}

#evil-17-container .controls__numbers .num-button:hover {
    background-color: var(--color-evil-primary);
    color: white;
}

#evil-17-container .button--hint {
    background: var(--color-evil-accent);
    color: black;
}

#evil-17-container .button--hint:hover {
    background: #FFEC8B;
}

#evil-17-container .sudoku-grid {
    box-shadow: var(--glow-evil);
}

/* Evil 17 Navigation Button */
.button--evil {
    background: linear-gradient(135deg, #ff6b6b 0%, #ee5a24 50%, #d63031 100%);
    border: 2px solid transparent;
    color: white;
    font-weight: 600;
    text-decoration: none;
    position: relative;
    overflow: hidden;
}

.button--evil::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s;
}

.button--evil:hover {
    background: linear-gradient(135deg, #ff5252 0%, #d32f2f 50%, #b71c1c 100%);
    box-shadow: 0 6px 25px rgba(255, 107, 107, 0.4);
    transform: translateY(-2px);
    border-color: rgba(255, 255, 255, 0.3);
}

.button--evil:hover::before {
    left: 100%;
}

.button--evil:active {
    transform: translateY(0);
    box-shadow: 0 3px 15px rgba(255, 107, 107, 0.3);
}

/* Mobile responsive for header buttons */
@media (max-width: 768px) {
    .header__actions {
        flex-wrap: wrap;
        gap: 8px;
    }
    
    .button--evil {
        flex: 1;
        min-width: 120px;
    }
}