/* ═══════════════════════════════════════════════════
   基础变量
   ═══════════════════════════════════════════════════ */
:root {
  --bg: #f0f2f5;
  --bg-card: #ffffff;
  --text: #1a1a2e;
  --text-secondary: #6b7280;
  --border: #e5e7eb;
  --primary: #6366f1;
  --primary-light: #eef2ff;
  --success: #10b981;
  --warning: #f59e0b;
  --danger: #ef4444;
  --info: #3b82f6;
  --radius: 16px;
  --radius-sm: 10px;
  --shadow: 0 1px 3px rgba(0,0,0,.06), 0 4px 12px rgba(0,0,0,.04);
  --shadow-lg: 0 4px 24px rgba(0,0,0,.1);
  --transition: .25s cubic-bezier(.4, 0, .2, 1);
  --font: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', system-ui, sans-serif;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; -webkit-font-smoothing: antialiased; }
body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  overflow-x: hidden;
}
.hidden { display: none !important; }

/* ═══════════════════════════════════════════════════
   认证页面
   ═══════════════════════════════════════════════════ */
#auth-view {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  padding: 24px;
}
.auth-container {
  width: 100%;
  max-width: 400px;
}
.auth-brand {
  text-align: center;
  color: #fff;
  margin-bottom: 32px;
}
.auth-logo {
  font-size: 3.5rem;
  margin-bottom: 8px;
  filter: drop-shadow(0 4px 12px rgba(0,0,0,.2));
}
.auth-brand h1 {
  font-size: 2rem;
  font-weight: 800;
  letter-spacing: 2px;
}
.auth-brand p {
  font-size: .85rem;
  opacity: .85;
  margin-top: 4px;
}

.auth-panel {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 28px 24px;
  box-shadow: var(--shadow-lg);
}
.form-group {
  margin-bottom: 16px;
}
.form-group label {
  display: block;
  font-size: .8rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 6px;
}
.form-group input {
  width: 100%;
  padding: 11px 14px;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: .95rem;
  font-family: var(--font);
  transition: border-color var(--transition);
  outline: none;
}
.form-group input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(99,102,241,.15);
}
.form-error {
  background: #fef2f2;
  color: var(--danger);
  font-size: .82rem;
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  margin-bottom: 12px;
}
.btn-auth {
  width: 100%;
  padding: 13px;
  border: none;
  border-radius: var(--radius-sm);
  background: var(--primary);
  color: #fff;
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: 4px;
  cursor: pointer;
  transition: opacity var(--transition), transform var(--transition);
}
.btn-auth:hover { opacity: .9; }
.btn-auth:active { transform: scale(.98); }
.btn-auth:disabled { opacity: .5; cursor: wait; }
.auth-switch {
  text-align: center;
  font-size: .82rem;
  color: var(--text-secondary);
  margin-top: 16px;
}
.auth-switch a {
  color: var(--primary);
  text-decoration: none;
  font-weight: 600;
}

body.no-nav .bottom-nav { display: none; }

/* ═══════════════════════════════════════════════════
   布局
   ═══════════════════════════════════════════════════ */
#main-app {
  max-width: 520px;
  margin: 0 auto;
  padding: 0 16px 100px;
}

/* ═══════════════════════════════════════════════════
   顶部
   ═══════════════════════════════════════════════════ */
.app-header {
  text-align: center;
  padding: 24px 0 16px;
}
.app-header h1 {
  font-size: 1.45rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--primary), #ec4899);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.app-header p {
  font-size: .82rem;
  color: var(--text-secondary);
  margin-top: 2px;
}

.section-title {
  font-size: .8rem;
  font-weight: 600;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 12px;
  margin-top: 16px;
}

/* ═══════════════════════════════════════════════════
   闪卡库选择器
   ═══════════════════════════════════════════════════ */
.library-selector {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 14px 18px;
  margin-bottom: 16px;
  box-shadow: var(--shadow);
  border-left: 4px solid var(--primary);
}

.library-label {
  display: flex;
  align-items: center;
  gap: 10px;
}

.library-icon {
  font-size: 1.8rem;
  flex-shrink: 0;
}

.library-name {
  flex: 1;
  font-size: 1.05rem;
  font-weight: 600;
}

.btn-change-library {
  padding: 6px 16px;
  border: 1.5px solid var(--primary);
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--primary);
  font-size: .85rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
}

.btn-change-library:hover {
  background: var(--primary);
  color: #fff;
}

/* ═══════════════════════════════════════════════════
   弹窗
   ═══════════════════════════════════════════════════ */
.modal {
  position: fixed;
  inset: 0;
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
}

.modal-overlay {
  position: absolute;
  inset: 0;
  background: rgba(0,0,0,.5);
  backdrop-filter: blur(4px);
}

.modal-content {
  position: relative;
  background: var(--bg-card);
  border-radius: var(--radius);
  max-width: 480px;
  width: 100%;
  max-height: 70vh;
  box-shadow: 0 20px 60px rgba(0,0,0,.3);
  display: flex;
  flex-direction: column;
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px;
  border-bottom: 1px solid var(--border);
}

.modal-header h2 {
  font-size: 1.2rem;
  font-weight: 700;
}

.modal-close {
  width: 32px;
  height: 32px;
  border: none;
  border-radius: 50%;
  background: var(--bg);
  color: var(--text-secondary);
  font-size: 1.5rem;
  line-height: 1;
  cursor: pointer;
  transition: background var(--transition);
}

.modal-close:hover {
  background: var(--border);
}

.modal-body {
  padding: 20px;
  overflow-y: auto;
}

/* 闪卡库网格布局 */
#library-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 16px;
}

.library-grid-item {
  background: var(--bg);
  border: 2px solid var(--border);
  border-radius: var(--radius-md);
  padding: 20px 12px;
  cursor: pointer;
  transition: all .2s ease;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
}

.library-grid-item:hover {
  background: var(--primary-light);
  border-color: var(--primary);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0,0,0,.1);
}

.library-grid-item.active {
  background: var(--primary-light);
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(88, 86, 214, 0.15);
}

.library-grid-icon {
  font-size: 2.5rem;
  line-height: 1;
}

.library-grid-name {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text);
  line-height: 1.3;
  word-break: break-word;
}

.library-grid-item.active .library-grid-name {
  color: var(--primary);
}

/* 响应式调整 */
@media (max-width: 768px) {
  #library-list {
    grid-template-columns: repeat(auto-fill, minmax(110px, 1fr));
    gap: 12px;
  }
  .library-grid-item {
    padding: 16px 8px;
  }
  .library-grid-icon {
    font-size: 2rem;
  }
  .library-grid-name {
    font-size: 0.85rem;
  }
}

.loading, .empty-hint, .error-hint {
  text-align: center;
  padding: 40px 0;
  color: var(--text-secondary);
  font-size: .9rem;
}
.error-hint { color: var(--danger); }

/* ═══════════════════════════════════════════════════
   牌组网格布局
   ═══════════════════════════════════════════════════ */
#deck-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
  margin-bottom: 20px;
}

/* ═══════════════════════════════════════════════════
   牌组卡片
   ═══════════════════════════════════════════════════ */
.deck-card {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
  border-top: 5px solid var(--deck-color, var(--primary));
  transition: transform var(--transition), box-shadow var(--transition), border-top-width var(--transition);
  display: flex;
  flex-direction: column;
  position: relative;
  overflow: hidden;
}

/* 添加柔和的渐变背景 */
.deck-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 80px;
  background: linear-gradient(180deg, 
    color-mix(in srgb, var(--deck-color) 8%, transparent) 0%, 
    transparent 100%);
  pointer-events: none;
  z-index: 0;
}

.deck-card > * {
  position: relative;
  z-index: 1;
}

.deck-card:hover { 
  transform: translateY(-6px); 
  box-shadow: 0 8px 32px rgba(0,0,0,.12);
  border-top-width: 6px;
}

.deck-card-header { display: flex; align-items: center; gap: 12px; margin-bottom: 14px; }
.deck-icon { 
  font-size: 2.4rem; 
  flex-shrink: 0;
  filter: drop-shadow(0 2px 4px rgba(0,0,0,0.1));
}
.deck-info { flex: 1; min-width: 0; }
.deck-name { 
  font-size: 1.1rem; 
  font-weight: 800; 
  white-space: nowrap; 
  overflow: hidden; 
  text-overflow: ellipsis;
  color: color-mix(in srgb, var(--deck-color) 80%, var(--text));
  text-shadow: 0 1px 2px rgba(0,0,0,0.03);
}
.deck-desc { 
  font-size: .75rem; 
  color: var(--text-secondary); 
  margin-top: 3px; 
  line-height: 1.4;
  font-weight: 500;
}

.deck-progress { margin-bottom: 12px; }
.progress-bar {
  height: 7px;
  background: color-mix(in srgb, var(--deck-color) 12%, var(--bg));
  border-radius: 4px;
  overflow: hidden;
  box-shadow: inset 0 1px 3px rgba(0,0,0,0.08);
}
.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, 
    var(--deck-color) 0%, 
    color-mix(in srgb, var(--deck-color) 120%, white) 100%);
  border-radius: 4px;
  transition: width .6s ease;
  box-shadow: 0 1px 3px color-mix(in srgb, var(--deck-color) 40%, transparent);
}
.progress-text {
  font-size: .72rem;
  color: var(--text-secondary);
  margin-top: 5px;
  text-align: right;
  font-weight: 500;
}

.deck-stats-row {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 8px;
  margin-bottom: 12px;
}
.deck-stat {
  background: linear-gradient(135deg, var(--bg) 0%, color-mix(in srgb, var(--bg) 95%, var(--deck-color)) 100%);
  padding: 10px 8px;
  border-radius: var(--radius-sm);
  text-align: center;
  border: 1.5px solid color-mix(in srgb, var(--deck-color) 15%, transparent);
  transition: transform 0.2s, border-color 0.2s;
}
.deck-stat:hover {
  transform: scale(1.03);
  border-color: color-mix(in srgb, var(--deck-color) 30%, transparent);
}
.deck-stat .stat-num { 
  display: block; 
  font-size: 1.2rem; 
  font-weight: 800;
  text-shadow: 0 1px 2px rgba(0,0,0,0.05);
}
.deck-stat .stat-num.new { color: #3b82f6; }
.deck-stat .stat-num.due { color: #ef4444; }
.deck-stat .stat-num.learning { color: #f59e0b; }
.deck-stat .stat-num.mastered { color: #10b981; }
.deck-stat .stat-label { 
  font-size: .68rem; 
  color: var(--text-secondary); 
  margin-top: 3px; 
  display: block;
  font-weight: 500;
}

.deck-btn-row {
  display: flex; gap: 8px;
}
.btn-study {
  flex: 1;
  padding: 12px;
  border: none;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, var(--deck-color) 0%, color-mix(in srgb, var(--deck-color) 85%, black) 100%);
  color: #fff;
  font-size: .95rem;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--transition);
  margin-top: auto;
  box-shadow: 0 2px 8px color-mix(in srgb, var(--deck-color) 30%, transparent);
  text-shadow: 0 1px 2px rgba(0,0,0,0.2);
}
.btn-study:hover { 
  transform: translateY(-2px); 
  box-shadow: 0 4px 16px color-mix(in srgb, var(--deck-color) 40%, transparent);
}
.btn-study:active { transform: translateY(0); }
.btn-browse {
  width: 44px; flex-shrink: 0;
  border: none; border-radius: var(--radius-sm);
  background: var(--bg-card); box-shadow: var(--shadow);
  font-size: 1.1rem; cursor: pointer;
  transition: all var(--transition);
  display: flex; align-items: center; justify-content: center;
}
.btn-browse:hover { background: var(--border); transform: translateY(-2px); }
.btn-browse:active { transform: translateY(0); }

/* ═══════════════════════════════════════════════════
   学习视图
   ═══════════════════════════════════════════════════ */
.study-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 0 10px;
}
.study-header-left { display: flex; align-items: center; gap: 10px; }
.btn-back {
  width: 36px; height: 36px;
  border: none; border-radius: 50%;
  background: var(--bg-card); box-shadow: var(--shadow);
  cursor: pointer; font-size: 1.1rem;
  display: flex; align-items: center; justify-content: center;
  transition: background var(--transition);
}
.btn-back:hover { background: var(--border); }
#study-deck-name { font-size: 1rem; font-weight: 600; }
.study-progress-bar { flex: 1; max-width: 120px; margin-left: 16px; text-align: right; }
#study-progress-text { font-size: .7rem; color: var(--text-secondary); margin-bottom: 4px; }

/* ── 浏览模式 ──────────────────────────────────── */
.browse-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 18px 0 14px;
}
.browse-header-left { display: flex; align-items: center; gap: 10px; }
#browse-deck-name { font-size: 1rem; font-weight: 600; }
#browse-count { font-size: .78rem; color: var(--text-secondary); }

.browse-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: 12px;
  padding-bottom: 100px;
}

.browse-card {
  perspective: 600px;
  cursor: pointer;
}
.browse-card-inner {
  position: relative;
  width: 100%; min-height: 120px;
  transform-style: preserve-3d;
  transition: transform .45s cubic-bezier(.4,.2,.2,1);
}
.browse-card-inner.flipped { transform: rotateY(180deg); }

.browse-card-face {
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: var(--radius-sm);
  background: var(--bg-card);
  box-shadow: var(--shadow);
  display: flex; flex-direction: column;
  align-items: center; justify-content: center;
  padding: 16px 12px;
  text-align: center;
  overflow-y: auto;
  min-height: 120px;
}

.browse-card-front {
  position: relative;
  border-top: 3px solid var(--primary);
}
.browse-card-back {
  position: absolute; inset: 0;
  transform: rotateY(180deg);
  border-top: 3px solid var(--success);
}

.browse-card-content {
  font-size: .88rem; font-weight: 600;
  line-height: 1.6; word-break: break-word;
}
.browse-card-content .katex { font-size: .95em; }

.browse-card-tag {
  position: absolute; bottom: 6px; right: 8px;
  font-size: .58rem; color: var(--text-secondary); opacity: .6;
}

.browse-card-example {
  margin-top: 8px; padding-top: 8px;
  border-top: 1px dashed rgba(0,0,0,.1);
  font-size: .74rem; font-weight: 400;
  color: var(--text-secondary); line-height: 1.5;
  word-break: break-word;
}

.browse-card-inner.flipped + .browse-card-tag { display: none; }

/* ── 闪念卡 ────────────────────────────────────── */
.card-container { perspective: 1200px; margin: 18px 0; }

#flashcard {
  width: 100%;
  min-height: 270px;
  position: relative;
  transform-style: preserve-3d;
  transition: transform .5s cubic-bezier(.4,.0,.2,1);
  cursor: pointer;
}
#flashcard.flipped { transform: rotateY(180deg); }

.card-face {
  position: absolute; inset: 0;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: var(--radius);
  background: var(--bg-card);
  box-shadow: var(--shadow-lg);
  display: flex; flex-direction: column;
  align-items: center; justify-content: center;
  padding: 32px 24px;
  text-align: center;
  overflow-y: auto;
}
.card-front { border-top: 4px solid var(--primary); }
.card-front::before {
  content: '信号';
  position: absolute; top: 14px; left: 18px;
  font-size: .62rem; font-weight: 600;
  color: var(--primary); letter-spacing: 2px; opacity: .55;
}
.card-back { transform: rotateY(180deg); border-top: 4px solid var(--success); }
.card-back::before {
  content: '动作';
  position: absolute; top: 14px; left: 18px;
  font-size: .62rem; font-weight: 600;
  color: var(--success); letter-spacing: 2px; opacity: .55;
}

.card-content { font-size: 1.2rem; font-weight: 600; line-height: 1.8; word-break: break-word; }

.card-example {
  margin-top: 16px; padding-top: 14px;
  border-top: 1px dashed rgba(0,0,0,.12);
  font-size: .92rem; font-weight: 400; line-height: 1.7;
  color: var(--text-secondary); word-break: break-word;
}
.card-example.hidden { display: none; }

.card-meta {
  position: absolute; bottom: 12px;
  display: flex; gap: 8px; font-size: .68rem;
}
.card-status { padding: 2px 10px; border-radius: 20px; font-weight: 600; }
.card-status.new { background: #dbeafe; color: #2563eb; }
.card-status.learning { background: #fef3c7; color: #d97706; }
.card-status.mastered { background: #d1fae5; color: #059669; }
#card-tag { padding: 2px 10px; border-radius: 20px; background: #f3f4f6; color: var(--text-secondary); }

.card-enter { animation: cardSlideIn .3s ease; }
@keyframes cardSlideIn { from { opacity:0; transform:translateX(40px); } to { opacity:1; transform:translateX(0); } }

.flip-hint { text-align: center; margin-top: 6px; font-size: .72rem; color: var(--text-secondary); }

/* ── 卡片反馈按钮 ──────────────────────────────── */
.btn-card-feedback {
  display: block;
  margin: 8px auto 0;
  padding: 4px 14px;
  border: 1px solid var(--border);
  border-radius: 20px;
  background: var(--bg-card);
  color: var(--text-secondary);
  font-size: .7rem;
  cursor: pointer;
  transition: all .2s;
}
.btn-card-feedback:hover {
  border-color: var(--warning);
  color: var(--warning);
  background: #fffbeb;
}

/* ── 操作按钮 ──────────────────────────────────── */
.action-area { margin-top: 14px; text-align: center; }

.btn-flip-main {
  width: 100%; padding: 14px;
  border: 2px dashed var(--border);
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--text-secondary);
  font-size: .92rem; font-weight: 500; cursor: pointer;
  transition: all var(--transition);
}
.btn-flip-main:hover { border-color: var(--primary); color: var(--primary); background: var(--primary-light); }

.rating-buttons { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; }
.btn-rate {
  padding: 12px 4px; border: none;
  border-radius: var(--radius-sm);
  font-size: .8rem; font-weight: 600;
  cursor: pointer; color: #fff;
  transition: transform var(--transition), box-shadow var(--transition);
}
.btn-rate:hover { transform: translateY(-2px); box-shadow: var(--shadow); }
.btn-rate:active { transform: scale(.96); }
.btn-rate.forgot { background: var(--danger); }
.btn-rate.hard   { background: var(--warning); }
.btn-rate.good   { background: var(--info); }
.btn-rate.easy   { background: var(--success); }
.btn-rate .rate-key { display: block; font-size: .58rem; opacity: .7; margin-top: 2px; }

/* ── 完成 ──────────────────────────────────────── */
.complete-card {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 40px 24px;
  text-align: center;
  box-shadow: var(--shadow-lg);
  animation: fadeUp .4s ease;
}
@keyframes fadeUp { from { opacity:0; transform:translateY(20px); } to { opacity:1; transform:translateY(0); } }
.complete-icon { font-size: 3rem; margin-bottom: 10px; }
.complete-title { font-size: 1.25rem; font-weight: 700; margin-bottom: 20px; }
.complete-stats { display: grid; grid-template-columns: repeat(3,1fr); gap: 12px; margin-bottom: 24px; }
.complete-stat-num { display: block; font-size: 1.4rem; font-weight: 700; color: var(--primary); }
.complete-stat-label { font-size: .7rem; color: var(--text-secondary); }
.btn-finish {
  padding: 12px 36px; border: none;
  border-radius: var(--radius-sm);
  background: var(--primary); color: #fff;
  font-size: 1rem; font-weight: 600; cursor: pointer;
  transition: opacity var(--transition);
}
.btn-finish:hover { opacity: .9; }

/* ═══════════════════════════════════════════════════
   统计
   ═══════════════════════════════════════════════════ */
.stats-overview { display: grid; grid-template-columns: repeat(2,1fr); gap: 12px; margin-bottom: 20px; }
.stats-card {
  background: var(--bg-card); border-radius: var(--radius-sm);
  padding: 16px; text-align: center; box-shadow: var(--shadow);
}
.stats-card .s-num { display: block; font-size: 1.5rem; font-weight: 700; color: var(--primary); }
.stats-card .s-label { font-size: .72rem; color: var(--text-secondary); margin-top: 2px; }

.stats-section {
  background: var(--bg-card); border-radius: var(--radius);
  padding: 20px; margin-bottom: 14px; box-shadow: var(--shadow);
}
.stats-section h3 { font-size: .88rem; font-weight: 700; margin-bottom: 14px; }

/* ── 库级别分组统计 ──────────────────────────────── */
.stats-lib-section { padding: 0; overflow: hidden; }

.stats-lib-header {
  display: flex; justify-content: space-between; align-items: center;
  padding: 16px 20px; cursor: pointer; user-select: none;
  transition: background .2s;
}
.stats-lib-header:active { background: var(--bg); }
.stats-lib-title { display: flex; align-items: center; gap: 8px; }
.stats-lib-icon { font-size: 1.2rem; }
.stats-lib-name { font-size: .92rem; font-weight: 700; }
.stats-lib-toggle {
  font-size: .8rem; color: var(--text-secondary);
  transition: transform .25s;
}
.stats-lib-section.collapsed .stats-lib-toggle { transform: rotate(-90deg); }

.stats-lib-summary {
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px;
  padding: 0 20px 12px; text-align: center;
}
.stats-lib-stat .sl-num {
  display: block; font-size: 1.1rem; font-weight: 700; color: var(--primary);
}
.stats-lib-stat .sl-label {
  font-size: .68rem; color: var(--text-secondary); margin-top: 2px;
}

.stats-lib-progress { padding: 0 20px 16px; }

.stats-lib-decks {
  padding: 0 20px 20px;
  border-top: 1px solid var(--bg);
  padding-top: 16px;
  transition: max-height .3s ease, opacity .25s ease;
  max-height: 2000px; opacity: 1; overflow: hidden;
}
.stats-lib-section.collapsed .stats-lib-decks {
  max-height: 0; opacity: 0; padding-top: 0; padding-bottom: 0; border-top: none;
}

/* ── 牌组条目 ────────────────────────────────────── */
.stats-deck-item { margin-bottom: 16px; }
.stats-deck-item:last-child { margin-bottom: 0; }
.stats-deck-header { display: flex; justify-content: space-between; font-size: .84rem; font-weight: 600; margin-bottom: 6px; }
.stats-deck-pct { color: var(--primary); }
.stats-deck-detail { display: flex; flex-wrap: wrap; gap: 12px; font-size: .68rem; color: var(--text-secondary); margin-top: 6px; }

.stats-deck-clickable {
  padding: 10px 12px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background .2s, transform .15s, box-shadow .2s;
  border: 1.5px solid transparent;
}
.stats-deck-clickable:hover {
  background: var(--primary-light);
  border-color: color-mix(in srgb, var(--primary) 25%, transparent);
  transform: translateX(2px);
}
.stats-deck-clickable:active {
  transform: scale(.98);
}
.stats-deck-action {
  font-size: .72rem;
  font-weight: 600;
  color: var(--primary);
  opacity: 0;
  transition: opacity .2s;
  white-space: nowrap;
}
.stats-deck-clickable:hover .stats-deck-action {
  opacity: 1;
}

/* ── 时长统计 ──────────────────────────────────── */
.time-stats-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.time-stat-card {
  background: var(--bg); border-radius: var(--radius-sm); padding: 14px;
}
.time-stat-header {
  font-size: .76rem; font-weight: 700; color: var(--primary);
  margin-bottom: 10px; text-align: center;
}
.time-stat-row {
  display: flex; justify-content: space-between; align-items: center;
  padding: 4px 0; font-size: .78rem;
}
.time-stat-label { color: var(--text-secondary); }
.time-stat-val { font-weight: 600; }
.time-stat-total {
  margin-top: 6px; padding-top: 6px;
  border-top: 1px solid var(--border);
}
.time-stat-total .time-stat-val { color: var(--primary); font-weight: 700; }

/* ── 热力图 ────────────────────────────────────── */
#heatmap { display: grid; grid-template-columns: repeat(7,1fr); gap: 4px; }
.heatmap-cell {
  aspect-ratio: 1; border-radius: 3px; background: var(--bg);
  display: flex; align-items: center; justify-content: center;
  font-size: .6rem; font-weight: 600; color: transparent;
}
.heatmap-cell.h1 { background: #c7d2fe; color: #4338ca; }
.heatmap-cell.h2 { background: #818cf8; color: #fff; }
.heatmap-cell.h3 { background: #4f46e5; color: #fff; }

/* ═══════════════════════════════════════════════════
   个人中心
   ═══════════════════════════════════════════════════ */
.profile-card {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
  margin-bottom: 16px;
}
.profile-top { display: flex; align-items: center; gap: 16px; margin-bottom: 20px; }
.profile-avatar {
  width: 56px; height: 56px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--primary), #ec4899);
  color: #fff;
  font-size: 1.5rem; font-weight: 700;
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0;
}
.profile-nickname { font-size: 1.15rem; font-weight: 700; }
.profile-username { font-size: .8rem; color: var(--text-secondary); }
.profile-joined { font-size: .72rem; color: var(--text-secondary); margin-top: 2px; }

.profile-points-bar {
  display: flex; align-items: center; justify-content: center;
  gap: 8px; padding: 10px 16px; margin-bottom: 12px;
  background: linear-gradient(135deg, #fef3c7 0%, #fde68a 100%);
  border-radius: var(--radius-sm); border: 1.5px solid #f59e0b;
}
.profile-points-bar .points-icon { font-size: 1.3rem; }
.profile-points-bar .points-value {
  font-size: 1.4rem; font-weight: 800;
  color: #92400e; letter-spacing: -.5px;
}
.profile-points-bar .points-label {
  font-size: .8rem; font-weight: 600; color: #b45309;
}

.profile-stats {
  display: grid; grid-template-columns: repeat(4, 1fr);
  gap: 8px; text-align: center;
}
.profile-stats .p-num { display: block; font-size: 1.1rem; font-weight: 700; color: var(--primary); }
.profile-stats .p-label { font-size: .64rem; color: var(--text-secondary); }

.profile-actions { display: flex; flex-direction: column; gap: 10px; }
.btn-outline {
  width: 100%; padding: 12px;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-card);
  font-size: .9rem; font-weight: 600; color: var(--text);
  cursor: pointer; transition: all var(--transition);
}
.btn-outline:hover { border-color: var(--primary); color: var(--primary); }
.btn-outline.danger { border-color: #fca5a5; color: var(--danger); }
.btn-outline.danger:hover { background: #fef2f2; }

/* ── 好友系统 ──────────────────────────────────── */
.friends-section {
  background: var(--bg-card); border-radius: var(--radius);
  box-shadow: var(--shadow);
}
.friends-section.collapsible {
  padding: 0;
}
.friends-section h3 { font-size: .95rem; font-weight: 700; margin: 0; }
.friends-section h4 { font-size: .82rem; font-weight: 600; color: var(--text-secondary); margin: 16px 0 10px; }

.friend-add-row { display: flex; gap: 8px; }
.friend-add-row input {
  flex: 1; padding: 8px 12px; border: 1.5px solid var(--border);
  border-radius: var(--radius-sm); font-size: .85rem;
  background: var(--bg); color: var(--text);
}
.friend-add-row input:focus { border-color: var(--primary); outline: none; }

.friend-msg {
  font-size: .78rem; margin-top: 8px; padding: 6px 10px;
  border-radius: var(--radius-sm);
}
.friend-msg.success { background: #ecfdf5; color: #047857; }
.friend-msg.error { background: #fef2f2; color: var(--danger); }

.friend-request-item {
  display: flex; justify-content: space-between; align-items: center;
  padding: 10px 0; border-bottom: 1px solid var(--bg);
}
.friend-request-item:last-child { border-bottom: none; }
.friend-request-info { display: flex; align-items: center; gap: 8px; }
.friend-request-actions { display: flex; gap: 6px; }

.friend-avatar {
  width: 32px; height: 32px; border-radius: 50%; flex-shrink: 0;
  background: linear-gradient(135deg, var(--primary), #ec4899);
  color: #fff; font-size: .8rem; font-weight: 700;
  display: flex; align-items: center; justify-content: center;
}
.friend-name { font-size: .85rem; font-weight: 600; }
.friend-uname { font-size: .72rem; color: var(--text-secondary); }

.friend-item {
  background: var(--bg); border-radius: var(--radius-sm);
  padding: 14px; margin-bottom: 10px;
}
.friend-item:last-child { margin-bottom: 0; }
.friend-item-top { display: flex; align-items: center; gap: 10px; margin-bottom: 8px; }
.friend-item-info { flex: 1; }
.friend-item-stats {
  display: flex; gap: 12px; font-size: .74rem; color: var(--text-secondary);
  padding: 8px 0; border-top: 1px dashed var(--border); border-bottom: 1px dashed var(--border);
  margin-bottom: 8px;
}
.friend-item-actions { display: flex; gap: 6px; justify-content: flex-end; }

/* ── 密码弹窗表单 ──────────────────────────────── */
#password-modal .modal-form form {
  padding: 20px;
}
#password-modal .form-group {
  margin-bottom: 12px;
}
#password-modal .form-group input {
  width: 100%; padding: 10px 12px; border: 1.5px solid var(--border);
  border-radius: var(--radius-sm); font-size: .88rem;
  background: var(--bg); color: var(--text); box-sizing: border-box;
}
#password-modal .form-group input:focus { border-color: var(--primary); outline: none; }

/* ═══════════════════════════════════════════════════
   底部导航
   ═══════════════════════════════════════════════════ */
.bottom-nav {
  position: fixed;
  bottom: 0; left: 0; right: 0;
  background: var(--bg-card);
  border-top: 1px solid var(--border);
  display: flex; justify-content: center;
  padding: 6px 0 env(safe-area-inset-bottom, 8px);
  z-index: 100;
  box-shadow: 0 -2px 10px rgba(0,0,0,.04);
}
.nav-item {
  flex: 1; max-width: 140px;
  display: flex; flex-direction: column; align-items: center; gap: 2px;
  padding: 8px 0; border: none; background: none;
  color: var(--text-secondary);
  font-size: .62rem; cursor: pointer;
  transition: color var(--transition);
}
.nav-item .nav-icon { font-size: 1.25rem; }
.nav-item.active { color: var(--primary); }

/* ═══════════════════════════════════════════════════
   KaTeX / 滚动条 / 响应式
   ═══════════════════════════════════════════════════ */
.katex { font-size: 1.1em; }
.card-content .katex { font-size: 1.2em; }

::-webkit-scrollbar { width: 4px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: #d1d5db; border-radius: 4px; }

@media (max-width: 480px) {
  #main-app { padding: 0 12px 90px; }
  .card-content { font-size: 1.05rem; }
  .deck-card { padding: 16px; }
  .auth-container { padding: 0; }
  
  /* 移动端单列布局 */
  #deck-grid {
    grid-template-columns: 1fr;
    gap: 12px;
  }
}

/* 平板端 2 列布局 */
@media (min-width: 481px) and (max-width: 768px) {
  #main-app { max-width: 720px; }
  #deck-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* 桌面端最多 3 列 */
@media (min-width: 769px) {
  #main-app { max-width: 960px; }
  #deck-grid {
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  }
}

/* ═══════════════════════════════════════════════════
   管理后台样式
   ═══════════════════════════════════════════════════ */

/* Header Actions */
.app-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 24px;
}

.header-actions {
  display: flex;
  gap: 12px;
  align-items: center;
}

.header-user {
  font-size: .85rem;
  font-weight: 600;
  color: var(--text-secondary);
  max-width: 100px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.btn-admin, .btn-logout {
  padding: 8px 16px;
  border: none;
  border-radius: 8px;
  font-size: .9rem;
  font-weight: 600;
  cursor: pointer;
  transition: all .2s;
}

.btn-admin {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
}

.btn-admin:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.3);
}

.btn-logout {
  background: #ef4444;
  color: white;
}

.btn-logout:hover {
  background: #dc2626;
}

/* Admin View */
#admin-view {
  padding: 20px;
  max-width: 1200px;
  margin: 0 auto;
}

.admin-header {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 24px;
  padding-bottom: 16px;
  border-bottom: 2px solid var(--border);
}

.admin-header h1 {
  flex: 1;
  font-size: 1.5rem;
  color: var(--text);
}

.admin-header-right {
  display: flex;
  align-items: center;
  gap: 12px;
}

#admin-user-info {
  font-size: .85rem;
  color: var(--text-secondary);
}

/* Admin Tabs */
.admin-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 24px;
  border-bottom: 2px solid var(--border);
  overflow-x: auto;
}

.admin-tab {
  padding: 12px 20px;
  border: none;
  background: none;
  font-size: .95rem;
  font-weight: 600;
  color: var(--text-secondary);
  cursor: pointer;
  border-bottom: 3px solid transparent;
  transition: all .2s;
  white-space: nowrap;
}

.admin-tab:hover {
  color: var(--primary);
}

.admin-tab.active {
  color: var(--primary);
  border-bottom-color: var(--primary);
}

/* Admin Section */
.admin-section {
  display: none;
}

.admin-section.active {
  display: block;
}

.admin-section-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}

.admin-section-header h2 {
  font-size: 1.3rem;
  color: var(--text);
}

/* Admin Filter */
.admin-filter {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-right: auto;
  margin-left: 20px;
}

.admin-filter label {
  font-size: .9rem;
  color: var(--text-secondary);
  font-weight: 600;
}

.admin-filter select {
  padding: 8px 12px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: .9rem;
  background: white;
  cursor: pointer;
}

/* Admin Table */
.admin-table-container {
  overflow-x: auto;
  background: white;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.admin-table {
  width: 100%;
  border-collapse: collapse;
  font-size: .9rem;
}

.admin-table th {
  background: var(--bg);
  padding: 12px;
  text-align: left;
  font-weight: 700;
  color: var(--text);
  border-bottom: 2px solid var(--border);
  white-space: nowrap;
}

.admin-table td {
  padding: 12px;
  border-bottom: 1px solid var(--border);
  color: var(--text);
}

.admin-table tbody tr:hover {
  background: var(--bg);
}

/* Admin Grid */
.admin-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 16px;
}

.admin-card {
  background: white;
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
  border-top: 4px solid var(--primary);
  transition: all .2s;
}

.admin-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.admin-card-header {
  display: flex;
  justify-content: space-between;
  align-items: start;
  margin-bottom: 12px;
}

.admin-card-icon {
  font-size: 2rem;
}

.admin-card-title {
  font-size: 1.1rem;
  font-weight: 700;
  margin: 8px 0;
}

.admin-card-desc {
  font-size: .85rem;
  color: var(--text-secondary);
  line-height: 1.4;
}

.admin-card-stats {
  display: flex;
  gap: 16px;
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--border);
  font-size: .85rem;
}

.admin-card-stat {
  color: var(--text-secondary);
}

.admin-card-stat strong {
  color: var(--primary);
  font-weight: 700;
}

.admin-card-actions {
  display: flex;
  gap: 8px;
  margin-top: 12px;
}

/* Stats Grid */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 16px;
  margin-top: 20px;
}

.stat-card {
  background: white;
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
  display: flex;
  gap: 16px;
  align-items: center;
  transition: all .2s;
}

.stat-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.stat-icon {
  font-size: 2.5rem;
  opacity: 0.8;
}

.stat-info {
  flex: 1;
}

.stat-label {
  font-size: .85rem;
  color: var(--text-secondary);
  margin-bottom: 4px;
  font-weight: 600;
}

.stat-value {
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--primary);
}

/* Buttons */
.btn-primary, .btn-secondary, .btn-danger, .btn-warning {
  padding: 8px 16px;
  border: none;
  border-radius: 6px;
  font-size: .85rem;
  font-weight: 600;
  cursor: pointer;
  transition: all .2s;
}

.btn-primary {
  background: var(--primary);
  color: white;
}

.btn-primary:hover {
  opacity: 0.9;
  transform: translateY(-1px);
}

.btn-secondary {
  background: var(--bg);
  color: var(--text);
}

.btn-secondary:hover {
  background: var(--border);
}

.btn-danger {
  background: var(--danger);
  color: white;
}

.btn-danger:hover {
  background: #dc2626;
}
.btn-warning {
  background: #f59e0b;
  color: white;
}
.btn-warning:hover {
  background: #d97706;
}

.btn-sm {
  padding: 4px 8px;
  font-size: .8rem;
}

/* Badge */
.badge {
  display: inline-block;
  padding: 4px 8px;
  border-radius: 4px;
  font-size: .75rem;
  font-weight: 700;
  white-space: nowrap;
}

.badge-success {
  background: #d1fae5;
  color: #065f46;
}

.badge-warning {
  background: #fef3c7;
  color: #92400e;
}

.badge-danger {
  background: #fee2e2;
  color: #991b1b;
}

.badge-info {
  background: #dbeafe;
  color: #1e40af;
}

/* Toggle Switch */
.toggle-switch {
  position: relative;
  display: inline-block;
  width: 44px;
  height: 24px;
}

.toggle-switch input {
  opacity: 0;
  width: 0;
  height: 0;
}

.toggle-slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: #ccc;
  transition: .3s;
  border-radius: 24px;
}

.toggle-slider:before {
  position: absolute;
  content: "";
  height: 18px;
  width: 18px;
  left: 3px;
  bottom: 3px;
  background-color: white;
  transition: .3s;
  border-radius: 50%;
}

.toggle-switch input:checked + .toggle-slider {
  background-color: var(--success);
}

.toggle-switch input:checked + .toggle-slider:before {
  transform: translateX(20px);
}

/* Modal Form */
.modal-form {
  max-width: 500px;
}

.modal-form form {
  padding: 20px;
  overflow-y: auto;
  max-height: calc(70vh - 65px);
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}

.form-group {
  margin-bottom: 16px;
}

.form-group label {
  display: block;
  margin-bottom: 6px;
  font-size: .9rem;
  font-weight: 600;
  color: var(--text);
}

.form-hint {
  font-size: .8rem;
  font-weight: 400;
  color: var(--text-secondary);
}

.form-group input[type="text"],
.form-group input[type="email"],
.form-group input[type="password"],
.form-group input[type="color"],
.form-group select,
.form-group textarea {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: .9rem;
  font-family: inherit;
  transition: border-color .2s;
  box-sizing: border-box;
  background: var(--card-bg);
  color: var(--text);
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--primary);
}

.form-group textarea {
  resize: vertical;
  min-height: 80px;
}

.checkbox-label {
  display: flex;
  align-items: center;
  gap: 8px;
  cursor: pointer;
  font-weight: 400;
}

.checkbox-label input[type="checkbox"] {
  width: 18px;
  height: 18px;
  cursor: pointer;
}

.form-error {
  padding: 10px;
  background: #fee2e2;
  color: #991b1b;
  border-radius: 6px;
  font-size: .85rem;
  margin-bottom: 16px;
}

.form-actions {
  display: flex;
  gap: 12px;
  justify-content: flex-end;
  padding-top: 16px;
  border-top: 1px solid var(--border);
}

/* Responsive */
@media (max-width: 768px) {
  #admin-view {
    padding: 12px;
  }
  
  .admin-section-header {
    flex-wrap: wrap;
    gap: 12px;
  }
  
  .admin-filter {
    margin-left: 0;
    order: 3;
    width: 100%;
  }
  
  .admin-table-container {
    overflow-x: scroll;
  }
  
  .admin-grid {
    grid-template-columns: 1fr;
  }
  
  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .form-row {
    grid-template-columns: 1fr;
  }
}

/* 修改密码 */
.change-password-section {
  background: var(--card-bg);
  border-radius: 16px;
  padding: 24px;
  margin-bottom: 16px;
  box-shadow: 0 2px 8px rgba(0,0,0,.06);
}

.change-password-section h3 {
  margin: 0 0 16px;
  font-size: 1.1rem;
  color: var(--text);
}

.change-password-form {
  max-width: 400px;
}

.change-password-form .form-row {
  display: block;
  margin-bottom: 12px;
}

.change-password-form input {
  width: 100%;
  padding: 10px 14px;
  border: 1px solid var(--border);
  border-radius: 10px;
  font-size: .95rem;
  background: var(--bg);
  color: var(--text);
  box-sizing: border-box;
}

.change-password-form input:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, .15);
}

.form-success {
  color: #10b981;
  font-size: .85rem;
  margin-top: 8px;
  padding: 8px 12px;
  background: rgba(16,185,129,.1);
  border-radius: 8px;
}

.admin-settings-form {
  max-width: 400px;
  margin: 0 auto;
  padding: 20px 0;
}

.btn-outline.btn-sm {
  padding: 6px 14px;
  font-size: .85rem;
  border-radius: 8px;
}

/* ═══════════════════════════════════════════════════
   吉伊卡哇图标系统 (Chiikawa Icon Sprite)
   ═══════════════════════════════════════════════════ */
.ckw-icon {
  display: inline-block;
  width: 56px;
  height: 56px;
  background-image: url('../images/Chiikawa.jpg');
  background-size: 500% 300%;
  background-repeat: no-repeat;
  flex-shrink: 0;
}
.ckw-icon.ckw-sm {
  width: 32px;
  height: 32px;
}
.ckw-icon.ckw-lg {
  width: 72px;
  height: 72px;
}

/* 5 列 x 3 行精灵图定位 */
.ckw-0  { background-position:   0%   0%; }
.ckw-1  { background-position:  25%   0%; }
.ckw-2  { background-position:  50%   0%; }
.ckw-3  { background-position:  75%   0%; }
.ckw-4  { background-position: 100%   0%; }
.ckw-5  { background-position:   0%  50%; }
.ckw-6  { background-position:  25%  50%; }
.ckw-7  { background-position:  50%  50%; }
.ckw-8  { background-position:  75%  50%; }
.ckw-9  { background-position: 100%  50%; }
.ckw-10 { background-position:   0% 100%; }
.ckw-11 { background-position:  25% 100%; }
.ckw-12 { background-position:  50% 100%; }
.ckw-13 { background-position:  75% 100%; }
.ckw-14 { background-position: 100% 100%; }

/* 图标风格切换开关 */
.icon-style-switch {
  display: flex;
  align-items: center;
  gap: 0;
  background: var(--bg);
  border-radius: 20px;
  padding: 3px;
  border: 1.5px solid var(--border);
}
.icon-style-btn {
  padding: 5px 14px;
  border: none;
  border-radius: 17px;
  background: transparent;
  font-size: .78rem;
  font-weight: 600;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition);
  white-space: nowrap;
}
.icon-style-btn.active {
  background: var(--primary);
  color: #fff;
  box-shadow: 0 2px 6px rgba(99,102,241,.3);
}
.icon-style-btn:hover:not(.active) {
  color: var(--primary);
  background: var(--primary-light);
}

/* 库选择器行：加入图标切换 */
.library-selector-row {
  display: flex;
  align-items: center;
  gap: 12px;
}
.library-selector-row .library-selector {
  flex: 1;
  margin-bottom: 0;
}

/* 吉伊卡哇模式下的牌组图标适配 */
.deck-icon:has(.ckw-icon) {
  filter: none;
  font-size: 0;
  line-height: 0;
}
.deck-card:hover .deck-icon .ckw-icon {
  transform: scale(1.1);
  transition: transform .25s ease;
}

/* 统计页面吉伊卡哇图标 */
.stats-deck-header .ckw-icon {
  vertical-align: middle;
  margin-right: 4px;
}

/* 学习页面头部吉伊卡哇图标 */
#study-deck-name .ckw-icon {
  vertical-align: middle;
  margin-right: 4px;
}

/* ═══ 提示弹窗 ═══ */
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }
@keyframes popUp { from { transform: scale(.85); opacity: 0; } to { transform: scale(1); opacity: 1; } }

#upgrade-prompt-overlay {
  position: fixed;
  inset: 0;
  z-index: 9999;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(0,0,0,.55);
  backdrop-filter: blur(6px);
  animation: fadeIn .3s ease;
}
#upgrade-prompt-overlay.hidden { display: none; }

.prompt-box {
  background: #fff;
  border-radius: 20px;
  padding: 36px 32px 28px;
  max-width: 360px;
  width: 90%;
  text-align: center;
  box-shadow: 0 20px 60px rgba(0,0,0,.25);
  animation: popUp .35s cubic-bezier(.34,1.56,.64,1);
}
.prompt-box-icon {
  font-size: 52px;
  margin-bottom: 8px;
}
.prompt-box h2 {
  font-size: 22px;
  font-weight: 700;
  color: #1a1a2e;
  margin: 0 0 10px;
}
.prompt-box-msg {
  font-size: 14px;
  color: #666;
  margin: 4px 0;
  line-height: 1.6;
}
.prompt-box .btn-auth {
  margin-top: 16px;
  width: 100%;
}

/* ═══ 锁定牌组 ═══ */
.deck-card.deck-locked {
  position: relative;
  opacity: .7;
  cursor: pointer;
  filter: grayscale(.3);
  transition: opacity .2s, filter .2s;
}
.deck-card.deck-locked:hover {
  opacity: .85;
  filter: grayscale(.1);
}
.deck-lock-icon {
  font-size: 22px;
  flex-shrink: 0;
  margin-left: auto;
}
.deck-locked-overlay {
  text-align: center;
  padding: 20px 0 8px;
}
.deck-locked-text {
  font-size: 16px;
  font-weight: 700;
  color: var(--primary);
  margin-bottom: 6px;
}
.deck-locked-count {
  font-size: 13px;
  color: var(--text-secondary);
}

/* ═══════════════════════════════════════════════════
   成就勋章系统
   ═══════════════════════════════════════════════════ */

/* 可折叠区块通用样式 */
.collapsible {
  background: var(--bg-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
}
.collapsible-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 20px;
  cursor: pointer;
  user-select: none;
  transition: background .2s;
}
.collapsible-header:active {
  background: var(--bg);
}
.collapsible-header h3 {
  font-size: .95rem;
  font-weight: 700;
  margin: 0;
}
.collapsible-toggle {
  font-size: .8rem;
  color: var(--text-secondary);
  transition: transform .25s;
}
.collapsible.collapsed .collapsible-toggle {
  transform: rotate(-90deg);
}
.collapsible-body {
  padding: 0 20px 20px;
  max-height: 2000px;
  opacity: 1;
  transition: max-height .3s ease, opacity .25s ease, padding .25s ease;
}
.collapsible.collapsed .collapsible-body {
  max-height: 0;
  opacity: 0;
  padding-top: 0;
  padding-bottom: 0;
  overflow: hidden;
}

/* 个人中心成就区 */
.achievements-section {
  background: var(--bg-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}
.achievements-section h3 {
  font-size: .95rem;
  font-weight: 700;
}
.achievements-section.collapsible {
  padding: 0;
}

.achievements-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(90px, 1fr));
  gap: 10px;
}

.achievement-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 12px 6px;
  border-radius: var(--radius-sm);
  text-align: center;
  transition: transform .2s, box-shadow .2s;
  cursor: default;
  position: relative;
}
.achievement-item:hover {
  transform: translateY(-3px);
  box-shadow: 0 4px 12px rgba(0,0,0,.1);
}

.achievement-item.earned {
  background: linear-gradient(145deg, #fef9c3 0%, #fef3c7 40%, #fde68a 100%);
  border: 1.5px solid #fbbf24;
}
.achievement-item.locked {
  background: var(--bg);
  border: 1.5px solid var(--border);
  opacity: .5;
  filter: grayscale(.8);
}

.achievement-badge {
  font-size: 1.8rem;
  line-height: 1;
  margin-bottom: 6px;
  position: relative;
}
.achievement-item.earned .achievement-badge {
  animation: badgePulse 2s ease-in-out infinite;
}

.achievement-name {
  font-size: .68rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.3;
  word-break: break-word;
}
.achievement-item.locked .achievement-name {
  color: var(--text-secondary);
}

.achievement-level-dots {
  display: flex;
  gap: 3px;
  margin-top: 4px;
}
.achievement-level-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--border);
}
.achievement-level-dot.filled {
  background: #f59e0b;
}
.achievement-item.locked .achievement-level-dot.filled {
  background: var(--text-secondary);
}

.achievement-progress-text {
  font-size: .58rem;
  color: var(--text-secondary);
  margin-top: 3px;
}

/* 成就分类标题 */
.achievement-category {
  grid-column: 1 / -1;
  font-size: .75rem;
  font-weight: 700;
  color: var(--text-secondary);
  padding: 8px 0 2px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 4px;
}
.achievement-category:first-child {
  padding-top: 0;
}

/* 成就弹窗 — 纯覆盖层，不影响底层视图状态 */
.achievement-popup {
  position: fixed;
  inset: 0;
  z-index: 10000;
  display: flex;
  align-items: flex-start;
  justify-content: center;
  padding-top: 80px;
  background: rgba(0,0,0,.35);
  backdrop-filter: blur(2px);
  cursor: pointer;
  transition: opacity .35s ease;
}
.achievement-popup.hidden {
  display: none;
}
.achievement-popup.fade-out {
  opacity: 0;
}

.achievement-popup-content {
  background: linear-gradient(145deg, #1a1a2e 0%, #16213e 100%);
  border: 2px solid #fbbf24;
  border-radius: 20px;
  padding: 32px 36px;
  text-align: center;
  box-shadow: 0 20px 60px rgba(0,0,0,.4), 0 0 80px rgba(251,191,36,.2);
  animation: achievementPopIn .6s cubic-bezier(.34,1.56,.64,1);
  cursor: default;
  position: relative;
  overflow: hidden;
  min-width: 260px;
}
.achievement-popup.fade-out .achievement-popup-content {
  animation: achievementPopOut .35s ease forwards;
}

.achievement-popup-glow {
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(ellipse at center, rgba(251,191,36,.15) 0%, transparent 60%);
  animation: glowRotate 3s linear infinite;
}

.achievement-popup-icon {
  font-size: 3.5rem;
  margin-bottom: 8px;
  position: relative;
  animation: badgeBounce .6s ease .3s both;
}

.achievement-popup-title {
  font-size: .8rem;
  font-weight: 700;
  color: #fbbf24;
  letter-spacing: 4px;
  text-transform: uppercase;
  margin-bottom: 8px;
  position: relative;
}

.achievement-popup-name {
  font-size: 1.3rem;
  font-weight: 800;
  color: #fff;
  margin-bottom: 6px;
  position: relative;
}

.achievement-popup-desc {
  font-size: .82rem;
  color: rgba(255,255,255,.7);
  position: relative;
}

.achievement-popup-level {
  margin-top: 10px;
  position: relative;
}
.achievement-popup-level .achievement-level-dots {
  justify-content: center;
}
.achievement-popup-level .achievement-level-dot {
  width: 8px;
  height: 8px;
  background: rgba(255,255,255,.2);
}
.achievement-popup-level .achievement-level-dot.filled {
  background: #fbbf24;
  box-shadow: 0 0 6px rgba(251,191,36,.5);
}

@keyframes achievementPopIn {
  from { transform: scale(.5) translateY(-30px); opacity: 0; }
  to   { transform: scale(1) translateY(0); opacity: 1; }
}
@keyframes achievementPopOut {
  from { transform: scale(1) translateY(0); opacity: 1; }
  to   { transform: scale(.8) translateY(-20px); opacity: 0; }
}
@keyframes badgeBounce {
  0%   { transform: scale(0) rotate(-20deg); }
  60%  { transform: scale(1.3) rotate(5deg); }
  100% { transform: scale(1) rotate(0deg); }
}
@keyframes badgePulse {
  0%, 100% { transform: scale(1); }
  50%      { transform: scale(1.08); }
}
@keyframes glowRotate {
  from { transform: rotate(0deg); }
  to   { transform: rotate(360deg); }
}

/* 好友勋章展示 */
.friend-achievements {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  padding-top: 6px;
}
.friend-achievement-badge {
  font-size: 1.1rem;
  line-height: 1;
  cursor: default;
  transition: transform .15s;
}
.friend-achievement-badge:hover {
  transform: scale(1.3);
}

/* 成就 tooltip */
.achievement-item[data-tooltip]::after {
  content: attr(data-tooltip);
  position: absolute;
  bottom: calc(100% + 6px);
  left: 50%;
  transform: translateX(-50%) scale(.9);
  background: rgba(0,0,0,.85);
  color: #fff;
  padding: 6px 10px;
  border-radius: 6px;
  font-size: .68rem;
  font-weight: 400;
  white-space: nowrap;
  pointer-events: none;
  opacity: 0;
  transition: opacity .2s, transform .2s;
  z-index: 10;
}
.achievement-item[data-tooltip]:hover::after {
  opacity: 1;
  transform: translateX(-50%) scale(1);
}

@media (max-width: 480px) {
  .achievements-grid {
    grid-template-columns: repeat(auto-fill, minmax(76px, 1fr));
    gap: 8px;
  }
  .achievement-badge { font-size: 1.5rem; }
  .achievement-name { font-size: .62rem; }
  .achievement-popup-content { padding: 24px 20px; min-width: 220px; }
  .achievement-popup-icon { font-size: 2.8rem; }
  .achievement-popup-name { font-size: 1.1rem; }
}

/* ═══════════════════════════════════════════════════
   反馈系统
   ═══════════════════════════════════════════════════ */

/* 反馈弹窗卡片预览 */
.feedback-card-info {
  padding: 0 20px;
}
.feedback-card-preview {
  background: var(--bg);
  border-left: 3px solid var(--primary);
  padding: 10px 14px;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  font-size: .82rem;
  margin-bottom: 4px;
  line-height: 1.6;
}
.feedback-card-preview .katex { font-size: .9em; }

/* 管理后台反馈列表 */
.feedback-admin-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.feedback-admin-item {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 16px 20px;
  box-shadow: var(--shadow);
  border-left: 4px solid var(--danger);
  transition: border-color .2s;
}
.feedback-admin-item.resolved {
  border-left-color: var(--success);
  opacity: .75;
}
.feedback-admin-item.ignored {
  border-left-color: var(--border);
  opacity: .6;
}

.feedback-admin-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 10px;
}

.feedback-admin-meta {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.feedback-admin-user {
  font-size: .82rem;
  font-weight: 600;
}

.feedback-admin-time {
  font-size: .72rem;
  color: var(--text-secondary);
}

.feedback-admin-actions {
  display: flex;
  gap: 6px;
}

.feedback-admin-card {
  background: var(--bg);
  border-left: 3px solid var(--info);
  padding: 8px 12px;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  font-size: .8rem;
  margin-bottom: 10px;
  line-height: 1.5;
}
.feedback-admin-card .text-secondary {
  color: var(--text-secondary);
  font-size: .72rem;
}

.feedback-admin-content {
  font-size: .88rem;
  line-height: 1.6;
  white-space: pre-wrap;
  word-break: break-word;
}

.feedback-admin-reply {
  margin-top: 10px;
  padding: 8px 12px;
  background: #ecfdf5;
  border-radius: var(--radius-sm);
  font-size: .82rem;
  color: #047857;
  line-height: 1.5;
}

.feedback-reply-row {
  margin-top: 10px;
  display: flex;
  gap: 8px;
}
.feedback-reply-input {
  flex: 1;
  padding: 8px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: .82rem;
  background: var(--bg);
  color: var(--text);
}
.feedback-reply-input:focus {
  outline: none;
  border-color: var(--primary);
}

@media (max-width: 768px) {
  .feedback-admin-header {
    flex-direction: column;
    align-items: flex-start;
  }
}