/* ===========================
   FlashInterview PWA 应用样式
   复用展示页暗色主题，更简洁实用
   =========================== */

:root {
  --bg: #0a0a0f;
  --bg-soft: #101019;
  --card-front: #151520;
  --card-back: #1a1a2e;
  --accent: #f59e0b;
  --accent-soft: rgba(245, 158, 11, 0.15);
  --accent-strong: #d97706;
  --success: #10b981;
  --success-soft: rgba(16, 185, 129, 0.15);
  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --border: rgba(148, 163, 184, 0.1);
  --border-strong: rgba(148, 163, 184, 0.2);
  --danger: #ef4444;
}

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

html { -webkit-text-size-adjust: 100%; }

body {
  font-family: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, sans-serif;
  background: var(--bg);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -webkit-tap-highlight-color: transparent;
  padding-bottom: 120px;
}

body::before {
  content: '';
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background:
    radial-gradient(ellipse 70% 40% at 50% -10%, rgba(245, 158, 11, 0.08), transparent),
    radial-gradient(ellipse 50% 30% at 90% 80%, rgba(99, 102, 241, 0.04), transparent);
  pointer-events: none;
  z-index: 0;
}

/* ===========================
   顶部栏
   =========================== */
.app-header {
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  background: rgba(10, 10, 15, 0.75);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  max-width: 720px;
  margin: 0 auto;
  padding: 14px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: 'Fraunces', serif;
  font-size: 18px;
  font-weight: 600;
  letter-spacing: -0.02em;
}

.logo-mark {
  width: 28px;
  height: 28px;
  background: linear-gradient(135deg, var(--accent), var(--accent-strong));
  border-radius: 7px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  color: #000;
  font-size: 13px;
}

.progress-counter {
  font-size: 13px;
  color: var(--text-secondary);
  font-family: 'Fraunces', serif;
  white-space: nowrap;
}

.progress-counter .num {
  color: var(--text-primary);
  font-weight: 600;
}

.progress-counter .num.accent {
  color: var(--accent);
}

/* header 右侧动作容器 */
.header-actions {
  display: flex;
  align-items: center;
  gap: 12px;
}

/* Chrome/Edge 安装按钮：beforeinstallprompt 触发后才显示 */
.install-btn {
  padding: 7px 14px;
  background: var(--accent);
  color: #000;
  border: none;
  border-radius: 100px;
  font-size: 13px;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  white-space: nowrap;
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  -webkit-tap-highlight-color: transparent;
}

.install-btn:hover {
  background: var(--accent-strong);
  transform: translateY(-1px);
}

/* iOS 安装提示横幅 */
.ios-hint {
  background: var(--accent);
  color: #000;
  padding: 10px 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  font-size: 13px;
  font-weight: 500;
}

.ios-hint[hidden] {
  display: none;
}

.ios-hint-text {
  flex: 1;
  text-align: center;
}

.ios-hint-close {
  background: none;
  border: none;
  color: #000;
  font-size: 20px;
  cursor: pointer;
  padding: 0;
  line-height: 1;
  opacity: 0.6;
  transition: opacity 0.2s;
}

.ios-hint-close:hover {
  opacity: 1;
}

/* ===========================
   筛选标签栏
   =========================== */
.filter-section {
  position: relative;
  z-index: 2;
  background: rgba(10, 10, 15, 0.6);
  border-bottom: 1px solid var(--border);
}

.filter-bar {
  max-width: 720px;
  margin: 0 auto;
  padding: 10px 20px;
  display: flex;
  gap: 8px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
  scrollbar-color: transparent transparent;
}

.filter-bar::-webkit-scrollbar {
  display: none;
}

.filter-bar + .filter-bar {
  border-top: 1px solid var(--border);
}

.pill {
  flex-shrink: 0;
  padding: 6px 14px;
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border-strong);
  border-radius: 100px;
  font-size: 13px;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  white-space: nowrap;
  -webkit-tap-highlight-color: transparent;
}

.pill:hover {
  color: var(--text-primary);
  border-color: var(--text-muted);
}

.pill.active {
  background: var(--accent);
  color: #000;
  border-color: var(--accent);
  font-weight: 600;
}

/* ===========================
   卡片舞台
   =========================== */
.card-stage {
  position: relative;
  z-index: 2;
  padding: 40px 20px 20px;
}

.card-wrapper {
  max-width: 500px;
  margin: 0 auto;
  position: relative;
}

.flashcard {
  position: relative;
  width: 100%;
  aspect-ratio: 3/4;
  max-height: 70vh;
  cursor: pointer;
  outline: none;
}

.flashcard:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 4px;
  border-radius: 22px;
}

/* 2D crossfade 翻转 —— 绝不使用 3D transform */
.card-face {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border-radius: 20px;
  padding: 32px 28px;
  display: flex;
  flex-direction: column;
  border: 1px solid var(--border-strong);
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.4);
  transition: opacity 0.4s cubic-bezier(0.4, 0, 0.2, 1),
              transform 0.4s cubic-bezier(0.4, 0, 0.2, 1);
  overflow: hidden;
}

.card-front {
  background: linear-gradient(145deg, var(--card-front), var(--bg-soft));
  z-index: 2;
  opacity: 1;
  transform: translateX(0);
}

.card-back {
  background: linear-gradient(145deg, var(--card-back), #16162a);
  z-index: 1;
  opacity: 0;
  transform: translateX(8px);
}

.flashcard.flipped .card-front {
  opacity: 0;
  transform: translateX(-8px);
  pointer-events: none;
}

.flashcard.flipped .card-back {
  opacity: 1;
  transform: translateX(0);
  z-index: 3;
}

/* 卡片内容 —— 正面 */
.card-label {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
  flex-shrink: 0;
}

.card-source {
  font-size: 12px;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-weight: 500;
}

.card-badge {
  padding: 3px 10px;
  background: var(--accent-soft);
  color: var(--accent);
  border-radius: 6px;
  font-size: 11px;
  font-weight: 500;
  letter-spacing: 0;
}

.card-question {
  font-family: 'Fraunces', serif;
  font-size: 24px;
  font-weight: 400;
  line-height: 1.4;
  letter-spacing: -0.01em;
  color: var(--text-primary);
  flex: 1;
  display: flex;
  align-items: center;
  overflow-y: auto;
  word-break: break-word;
}

.card-hint {
  margin-top: 20px;
  padding-top: 18px;
  border-top: 1px solid var(--border);
  font-size: 13px;
  color: var(--text-muted);
  text-align: center;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  flex-shrink: 0;
}

.hint-icon {
  font-size: 14px;
}

/* 卡片内容 —— 背面 */
.card-answer {
  font-size: 14px;
  line-height: 1.75;
  color: var(--text-secondary);
  flex: 1;
  overflow-y: auto;
  white-space: pre-line;
  word-break: break-word;
  padding-right: 4px;
}

.card-answer::-webkit-scrollbar {
  width: 4px;
}

.card-answer::-webkit-scrollbar-thumb {
  background: var(--border-strong);
  border-radius: 2px;
}

.card-actions {
  margin-top: 20px;
  padding-top: 18px;
  border-top: 1px solid var(--border);
  display: flex;
  gap: 12px;
  flex-shrink: 0;
}

.card-btn {
  flex: 1;
  padding: 11px 14px;
  border: none;
  border-radius: 10px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  font-family: inherit;
  -webkit-tap-highlight-color: transparent;
}

.card-btn-known {
  background: var(--success-soft);
  color: var(--success);
  border: 1px solid rgba(16, 185, 129, 0.3);
}

.card-btn-known:hover,
.card-btn-known:active {
  background: rgba(16, 185, 129, 0.25);
}

.card-btn-review {
  background: var(--accent-soft);
  color: var(--accent);
  border: 1px solid rgba(245, 158, 11, 0.3);
}

.card-btn-review:hover,
.card-btn-review:active {
  background: rgba(245, 158, 11, 0.25);
}

/* ===========================
   空池提示
   =========================== */
.empty-state {
  text-align: center;
  padding: 80px 24px;
  color: var(--text-secondary);
}

.empty-icon {
  font-size: 48px;
  margin-bottom: 16px;
  opacity: 0.7;
}

.empty-title {
  font-family: 'Fraunces', serif;
  font-size: 20px;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 8px;
}

.empty-desc {
  font-size: 14px;
  color: var(--text-muted);
  line-height: 1.6;
}

/* ===========================
   浮动添加按钮
   =========================== */
.fab {
  position: fixed;
  bottom: 28px;
  right: 24px;
  z-index: 100;
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 13px 22px;
  background: linear-gradient(135deg, var(--accent), var(--accent-strong));
  color: #000;
  border: none;
  border-radius: 100px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  box-shadow: 0 8px 30px rgba(245, 158, 11, 0.4);
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  font-family: inherit;
  -webkit-tap-highlight-color: transparent;
}

.fab:hover {
  transform: translateY(-3px) scale(1.02);
  box-shadow: 0 12px 40px rgba(245, 158, 11, 0.5);
}

.fab:active {
  transform: translateY(-1px) scale(0.98);
}

.fab-icon {
  font-size: 20px;
  font-weight: 400;
  line-height: 1;
}

/* ===========================
   添加题目弹窗
   =========================== */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.6);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  z-index: 200;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s ease, visibility 0.3s ease;
  padding: 20px;
}

.modal-overlay.active {
  opacity: 1;
  visibility: visible;
}

.modal {
  background: var(--card-front);
  border: 1px solid var(--border-strong);
  border-radius: 20px;
  width: 100%;
  max-width: 520px;
  max-height: 90vh;
  overflow-y: auto;
  transform: translateY(20px) scale(0.96);
  transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  box-shadow: 0 30px 80px rgba(0, 0, 0, 0.5);
}

.modal-overlay.active .modal {
  transform: translateY(0) scale(1);
}

.modal-header {
  padding: 24px 28px 18px;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  position: sticky;
  top: 0;
  background: var(--card-front);
  z-index: 1;
}

.modal-header h3 {
  font-family: 'Fraunces', serif;
  font-size: 20px;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.modal-close {
  width: 32px;
  height: 32px;
  border: none;
  background: transparent;
  color: var(--text-muted);
  font-size: 22px;
  cursor: pointer;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
  line-height: 1;
  font-family: inherit;
}

.modal-close:hover {
  background: var(--bg-soft);
  color: var(--text-primary);
}

.modal-body {
  padding: 22px 28px;
  display: flex;
  flex-direction: column;
  gap: 18px;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 7px;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}

.form-label {
  font-size: 13px;
  font-weight: 500;
  color: var(--text-secondary);
}

.form-input {
  padding: 11px 14px;
  background: var(--bg-soft);
  border: 1px solid var(--border-strong);
  border-radius: 10px;
  color: var(--text-primary);
  font-size: 14px;
  font-family: inherit;
  transition: border-color 0.2s, box-shadow 0.2s;
  outline: none;
  width: 100%;
}

.form-input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.form-input::placeholder {
  color: var(--text-muted);
}

.form-textarea {
  resize: vertical;
  min-height: 90px;
  line-height: 1.6;
}

.modal-footer {
  padding: 18px 28px 24px;
  display: flex;
  gap: 12px;
  justify-content: flex-end;
  border-top: 1px solid var(--border);
}

.btn {
  padding: 10px 22px;
  border: none;
  border-radius: 10px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  font-family: inherit;
  -webkit-tap-highlight-color: transparent;
}

.btn-primary {
  background: var(--accent);
  color: #000;
}

.btn-primary:hover {
  background: var(--accent-strong);
  transform: translateY(-1px);
}

.btn-secondary {
  background: transparent;
  color: var(--text-primary);
  border: 1px solid var(--border-strong);
}

.btn-secondary:hover {
  background: var(--bg-soft);
  border-color: var(--text-muted);
}

/* ===========================
   Modal Tabs
   =========================== */
.modal-tabs {
  display: flex;
  border-bottom: 1px solid var(--border);
}

.modal-tab {
  flex: 1;
  padding: 12px 16px;
  background: transparent;
  border: none;
  color: var(--text-muted);
  font-size: 14px;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
  border-bottom: 2px solid transparent;
  transition: all 0.2s;
}

.modal-tab:hover {
  color: var(--text-secondary);
}

.modal-tab.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

.tab-panel {
  display: none;
}

.tab-panel.active {
  display: flex;
}

.form-textarea-lg {
  min-height: 240px;
  font-size: 13px;
  line-height: 1.7;
}

/* ===========================
   Toast
   =========================== */
.toast {
  position: fixed;
  bottom: 100px;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  z-index: 300;
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 13px 24px;
  background: var(--success);
  color: #000;
  border-radius: 12px;
  font-size: 14px;
  font-weight: 500;
  box-shadow: 0 8px 30px rgba(16, 185, 129, 0.4);
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s cubic-bezier(0.4, 0, 0.2, 1),
              transform 0.3s cubic-bezier(0.4, 0, 0.2, 1),
              visibility 0.3s;
  pointer-events: none;
}

.toast.show {
  opacity: 1;
  visibility: visible;
  transform: translateX(-50%) translateY(0);
}

.toast-icon {
  font-size: 16px;
  font-weight: 700;
}

/* ===========================
   响应式
   =========================== */
@media (max-width: 600px) {
  .header-inner {
    padding: 12px 16px;
  }

  .logo {
    font-size: 16px;
  }

  .logo-mark {
    width: 26px;
    height: 26px;
    font-size: 12px;
  }

  .progress-counter {
    font-size: 12px;
  }

  .filter-bar {
    padding: 8px 16px;
  }

  .pill {
    padding: 6px 12px;
    font-size: 12px;
  }

  .card-stage {
    padding: 24px 16px 16px;
  }

  .card-wrapper {
    max-width: 100%;
  }

  .card-face {
    padding: 24px 22px;
    border-radius: 18px;
  }

  .card-question {
    font-size: 20px;
  }

  .card-answer {
    font-size: 13px;
  }

  .fab {
    bottom: 20px;
    right: 16px;
    padding: 12px 18px;
    font-size: 13px;
  }

  .fab-label {
    display: none;
  }

  .fab-icon {
    font-size: 22px;
  }

  .modal-body {
    padding: 20px 22px;
  }

  .modal-header {
    padding: 20px 22px 16px;
  }

  .modal-footer {
    padding: 16px 22px 22px;
  }

  .form-row {
    grid-template-columns: 1fr;
  }

  .toast {
    bottom: 88px;
    font-size: 13px;
    padding: 12px 20px;
  }
}

/* 超小屏（iPhone SE 等） */
@media (max-width: 360px) {
  .card-question {
    font-size: 18px;
  }

  .card-face {
    padding: 20px 18px;
  }
}