/* ════════════════════════════════════════════════
   Concept Explainer
   ════════════════════════════════════════════════ */

/* ══════════════════════════════════ CONCEPT EXPLAINER ══ */

/* Floating popup */
.ce-popup {
    position: fixed;
    z-index: 9998;
    width: 280px;
    background: #16163a;
    border: 1px solid rgba(139,92,246,0.4);
    border-radius: 16px;
    box-shadow: 0 16px 48px rgba(0,0,0,0.6), 0 0 0 1px rgba(139,92,246,0.1);
    display: none;
    opacity: 0;
    transform: translateY(4px) scale(0.97);
    transition: opacity 0.18s ease, transform 0.18s ease;
    overflow: hidden;
}
.ce-popup.ce-visible {
    opacity: 1;
    transform: translateY(0) scale(1);
}

.ce-header {
    display: flex; align-items: center; justify-content: space-between;
    padding: 12px 14px 8px;
    background: rgba(139,92,246,0.1);
    border-bottom: 1px solid rgba(139,92,246,0.15);
}
.ce-term {
    font-size: 14px; font-weight: 700;
    color: #c4b5fd;
    flex: 1; overflow: hidden;
    text-overflow: ellipsis; white-space: nowrap;
}
.ce-close {
    background: none; border: none;
    color: #555; font-size: 16px; cursor: pointer;
    padding: 0 0 0 8px; line-height: 1;
    transition: color 0.15s;
}
.ce-close:hover { color: #aaa; }

.ce-body { padding: 12px 14px; min-height: 48px; }

.ce-explanation {
    font-size: 13px; color: #bbb; line-height: 1.6;
    margin: 0;
}

.ce-loading {
    display: flex; align-items: center; gap: 10px;
    color: #666; font-size: 12px;
}
.ce-spinner {
    width: 14px; height: 14px; border-radius: 50%;
    border: 2px solid rgba(139,92,246,0.2);
    border-top-color: #8b5cf6;
    animation: spin 0.7s linear infinite;
    flex-shrink: 0;
}
@keyframes spin { to { transform: rotate(360deg); } }

.ce-error { font-size: 12px; color: #ef4444; margin: 0; }

.ce-footer {
    padding: 0 14px 12px;
}
.ce-ask-btn {
    width: 100%; padding: 7px 10px; border-radius: 10px;
    border: 1px solid rgba(139,92,246,0.25);
    background: rgba(139,92,246,0.08);
    color: #a78bfa; font-size: 11.5px; cursor: pointer;
    transition: all 0.15s; text-align: left;
}
.ce-ask-btn:hover { background: rgba(139,92,246,0.18); border-color: rgba(139,92,246,0.4); }

/* Explainable zones: text cursor */
.transcript-line, .overview-text, .takeaway-item,
.chapter-desc, .chapter-title, .summary-text {
    cursor: text;
    user-select: text;
    -webkit-user-select: text;
}

/* Floating explain trigger button */
#ceExplainBtn, .ce-trigger-btn {
    position: absolute;
    z-index: 9999;
    display: flex;
    align-items: center;
    gap: 5px;
    padding: 6px 13px;
    border-radius: 99px;
    border: 1px solid rgba(139,92,246,0.5);
    background: linear-gradient(135deg, #4c1d95, #6d28d9);
    color: #fff;
    font-size: 12px;
    font-weight: 600;
    cursor: pointer;
    box-shadow: 0 4px 16px rgba(109,40,217,0.5);
    opacity: 0;
    transition: opacity 0.15s ease, transform 0.15s ease;
    transform: translateY(2px);
    white-space: nowrap;
    pointer-events: auto;
}
#ceExplainBtn:hover, .ce-trigger-btn:hover {
    background: linear-gradient(135deg, #5b21b6, #7c3aed);
    box-shadow: 0 6px 20px rgba(109,40,217,0.65);
    transform: translateY(-1px) scale(1.03);
}

/* Hint pill */
.ce-hint-pill {
    position: fixed; bottom: 80px; left: 50%;
    transform: translateX(-50%) translateY(20px);
    background: rgba(139,92,246,0.9);
    color: #fff; font-size: 12px; font-weight: 500;
    padding: 8px 16px; border-radius: 99px;
    z-index: 9990; pointer-events: none;
    opacity: 0; transition: all 0.35s ease;
    white-space: nowrap;
    box-shadow: 0 4px 20px rgba(139,92,246,0.4);
}
.ce-hint-pill.ce-hint-visible {
    opacity: 1; transform: translateX(-50%) translateY(0);
}

/* Light mode */
html.light-mode .ce-popup {
    background: #fff;
    border-color: rgba(109,40,217,0.25);
    box-shadow: 0 12px 40px rgba(0,0,0,0.1);
}
html.light-mode .ce-header { background: rgba(109,40,217,0.06); border-bottom-color: rgba(109,40,217,0.12); }
html.light-mode .ce-term   { color: #7c3aed; }
html.light-mode .ce-close  { color: #bbb; }
html.light-mode .ce-close:hover { color: #666; }
html.light-mode .ce-explanation { color: #374151; }
html.light-mode .ce-ask-btn { background: rgba(109,40,217,0.06); border-color: rgba(109,40,217,0.18); color: #7c3aed; }
html.light-mode .ce-ask-btn:hover { background: rgba(109,40,217,0.12); }
html.light-mode .ce-hint-pill { background: rgba(109,40,217,0.88); }

/* ── Light mode: Chat panel ── */
html.light-mode .chat-panel {
    background: #ffffff;
    border-color: rgba(109,40,217,0.18);
    box-shadow: 0 16px 56px rgba(0,0,0,0.12);
}
html.light-mode .chat-panel-header {
    background: linear-gradient(135deg, rgba(109,40,217,0.07), rgba(79,70,229,0.05));
    border-bottom-color: rgba(109,40,217,0.1);
}
html.light-mode .chat-header-title { color: #1e1b4b; }
html.light-mode .chat-header-sub   { color: #9ca3af; }
html.light-mode .chat-close-btn {
    background: rgba(0,0,0,0.05);
    color: #6b7280;
}
html.light-mode .chat-close-btn:hover {
    background: rgba(0,0,0,0.1);
    color: #1e1b4b;
}
html.light-mode .chat-clear-btn {
    background: rgba(239,68,68,0.06);
    color: #ef4444;
}
html.light-mode .chat-messages {
    background: #f8f9ff;
}
html.light-mode .chat-messages::-webkit-scrollbar-thumb {
    background: rgba(109,40,217,0.2);
}
html.light-mode .chat-msg.assistant .chat-bubble {
    background: #ffffff;
    color: #374151;
    border-color: rgba(0,0,0,0.08);
    box-shadow: 0 2px 8px rgba(0,0,0,0.06);
}
html.light-mode .chat-msg.user .chat-bubble {
    background: linear-gradient(135deg, #6d28d9, #7c3aed);
    color: #fff;
}
html.light-mode .chat-ts-link {
    color: #7c3aed;
    background: rgba(109,40,217,0.08);
}
html.light-mode .chat-ts-link:hover {
    background: rgba(109,40,217,0.16);
}
html.light-mode .chat-suggestions {
    border-top-color: rgba(0,0,0,0.06);
    background: #fff;
}
html.light-mode .chat-suggestion-btn {
    background: rgba(109,40,217,0.06);
    border-color: rgba(109,40,217,0.2);
    color: #7c3aed;
}
html.light-mode .chat-suggestion-btn:hover {
    background: rgba(109,40,217,0.14);
    border-color: rgba(109,40,217,0.35);
}
html.light-mode .chat-input-area {
    border-top-color: rgba(0,0,0,0.06);
    background: #fff;
}
html.light-mode .chat-input {
    background: #f3f4f6;
    border-color: rgba(0,0,0,0.08);
    color: #1e1b4b;
}
html.light-mode .chat-input:focus {
    border-color: rgba(109,40,217,0.4);
    background: #fff;
}
html.light-mode .chat-input::placeholder { color: #9ca3af; }
html.light-mode .chat-send-btn {
    background: linear-gradient(135deg, #6d28d9, #7c3aed);
}
html.light-mode .typing-indicator span { background: #a78bfa; }

/* -- History search bar -------------------------- */
.hist-search-wrap {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 12px;
    border-bottom: 1px solid var(--border);
    flex-shrink: 0;
}
.hist-search-input {
    flex: 1;
    background: none;
    border: none;
    outline: none;
    font-family: var(--font);
    font-size: 12px;
    color: var(--text-primary);
}
.hist-search-input::placeholder { color: var(--text-muted); }

/* -- Video Length Warning Modal ------------------------ */
.vlen-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.75);
    backdrop-filter: blur(6px);
    z-index: 9000;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
    animation: fadeIn 0.2s ease;
}
.vlen-modal {
    background: #0f0f23;
    border: 1px solid rgba(139,92,246,0.3);
    border-radius: 20px;
    padding: 36px 32px;
    max-width: 420px;
    width: 100%;
    text-align: center;
    box-shadow: 0 32px 80px rgba(0,0,0,0.8);
    animation: slideUp 0.25s ease;
}
.vlen-icon { font-size: 48px; margin-bottom: 16px; }
.vlen-title {
    font-size: 18px;
    font-weight: 800;
    color: var(--text-primary);
    margin-bottom: 14px;
    letter-spacing: -0.3px;
}
.vlen-body {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 28px;
}
.vlen-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
}
.vlen-btn {
    padding: 10px 24px;
    border-radius: 12px;
    font-family: var(--font);
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    border: 1px solid var(--border);
}
.vlen-cancel {
    background: var(--bg-card);
    color: var(--text-secondary);
}
.vlen-cancel:hover { border-color: var(--accent); color: var(--text-primary); }
.vlen-confirm {
    background: linear-gradient(135deg, var(--accent), var(--accent-dark));
    color: white;
    border-color: transparent;
    box-shadow: 0 4px 16px rgba(109,40,217,0.4);
}
.vlen-confirm:hover { transform: translateY(-1px); box-shadow: 0 8px 24px rgba(109,40,217,0.5); }

/* ── Confirm Delete Modal ──────────────────────── */
.confirm-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.7);
    backdrop-filter: blur(6px);
    z-index: 9500;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
    animation: fadeIn 0.15s ease;
}
.confirm-modal {
    background: var(--bg-card);
    border: 1px solid rgba(239,68,68,0.3);
    border-radius: 18px;
    padding: 32px 28px;
    max-width: 360px;
    width: 100%;
    text-align: center;
    box-shadow: 0 24px 64px rgba(0,0,0,0.7);
    animation: slideUp 0.2s ease;
}
.confirm-icon { font-size: 40px; margin-bottom: 12px; }
.confirm-msg {
    font-size: 15px;
    color: var(--text-primary);
    line-height: 1.6;
    margin-bottom: 24px;
    font-weight: 500;
}
.confirm-actions { display: flex; gap: 12px; justify-content: center; }
.confirm-btn {
    padding: 10px 28px;
    border-radius: 12px;
    font-family: var(--font);
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    border: 1px solid var(--border);
}
.confirm-cancel {
    background: var(--bg-card);
    color: var(--text-secondary);
}
.confirm-cancel:hover { border-color: var(--accent); color: var(--text-primary); }
.confirm-delete {
    background: linear-gradient(135deg, #ef4444, #dc2626);
    color: white;
    border-color: transparent;
    box-shadow: 0 4px 16px rgba(239,68,68,0.35);
}
.confirm-delete:hover { transform: translateY(-1px); box-shadow: 0 8px 24px rgba(239,68,68,0.5); }

/* ── Compare Modal ──────────────────────── */
.compare-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.75);
    backdrop-filter: blur(8px);
    z-index: 9600;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
    animation: fadeIn 0.15s ease;
}
.compare-modal {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 20px;
    width: 95vw;
    max-width: 1100px;
    max-height: 85vh;
    display: flex;
    flex-direction: column;
    box-shadow: 0 24px 80px rgba(0,0,0,0.6);
    animation: slideUp 0.25s ease;
}
.compare-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 24px;
    border-bottom: 1px solid var(--border);
    flex-shrink: 0;
}
.compare-header h2 {
    font-size: 18px;
    font-weight: 700;
    color: var(--text-primary);
    margin: 0;
}
.compare-close {
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 28px;
    cursor: pointer;
    padding: 0 4px;
    line-height: 1;
    transition: color 0.2s;
}
.compare-close:hover { color: var(--accent); }
.compare-body {
    overflow-y: auto;
    padding: 24px;
    flex: 1;
}
.compare-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
}
.compare-col {
    background: var(--bg-main);
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 18px;
    display: flex;
    flex-direction: column;
    gap: 16px;
}
.compare-col-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-bottom: 12px;
    border-bottom: 1px solid var(--border);
}
.compare-label {
    font-size: 11px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    padding: 4px 10px;
    border-radius: 6px;
}
.compare-label-a { background: rgba(139,92,246,0.15); color: #a78bfa; }
.compare-label-b { background: rgba(59,130,246,0.15); color: #60a5fa; }
.compare-meta {
    font-size: 12px;
    color: var(--text-secondary);
}
.compare-section {
    margin-bottom: 4px;
}
.compare-section-title {
    font-size: 12px;
    font-weight: 700;
    color: var(--accent);
    text-transform: uppercase;
    letter-spacing: 0.3px;
    margin-bottom: 8px;
}
.compare-text {
    font-size: 13px;
    color: var(--text-primary);
    line-height: 1.7;
}
.compare-list {
    list-style: none;
    padding: 0;
    margin: 0;
}
.compare-list li {
    font-size: 13px;
    color: var(--text-primary);
    padding: 4px 0;
    border-bottom: 1px solid rgba(255,255,255,0.05);
    line-height: 1.5;
}
.compare-list li::before {
    content: "\2022  ";
    color: var(--accent);
    font-weight: 700;
}
.compare-diff-badge {
    display: inline-block;
    font-size: 10px;
    font-weight: 700;
    padding: 2px 8px;
    border-radius: 4px;
    margin-left: 8px;
}
.compare-diff-same { background: rgba(16,185,129,0.15); color: #34d399; }
.compare-diff-diff { background: rgba(251,191,36,0.15); color: #fbbf24; }
.compare-stats {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
    margin-bottom: 20px;
}
.compare-stat {
    text-align: center;
    padding: 12px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
}
.compare-stat-num {
    font-size: 22px;
    font-weight: 800;
    color: var(--accent);
}
.compare-stat-label {
    font-size: 11px;
    color: var(--text-secondary);
    margin-top: 2px;
}
@media (max-width: 700px) {
    .compare-grid { grid-template-columns: 1fr; }
    .compare-stats { grid-template-columns: 1fr 1fr; }
}

/* ── History Compare Button ──────────────── */
.hist-compare {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 6px;
    border-radius: 8px;
    transition: all 0.2s;
    flex-shrink: 0;
    opacity: 0;
}
.hist-item:hover .hist-compare { opacity: 1; }
.hist-compare:hover {
    color: var(--accent);
    background: rgba(139,92,246,0.1);
}

/* ── Video Tags ──────────────────────── */
.hist-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 4px;
    margin-top: 4px;
}
.hist-tag {
    display: inline-flex;
    align-items: center;
    gap: 3px;
    padding: 1px 8px;
    border-radius: 6px;
    font-size: 10px;
    font-weight: 600;
    white-space: nowrap;
    transition: all 0.2s;
}
.hist-tag-x {
    cursor: pointer;
    margin-left: 2px;
    opacity: 0;
    font-size: 12px;
    transition: opacity 0.2s;
}
.hist-tag:hover .hist-tag-x { opacity: 1; }
.hist-tag-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 6px;
    border-radius: 8px;
    transition: all 0.2s;
    flex-shrink: 0;
    opacity: 0;
    position: relative;
}
.hist-item:hover .hist-tag-btn { opacity: 1; }
.hist-tag-btn:hover {
    color: var(--accent);
    background: rgba(139,92,246,0.1);
}

/* Tag Picker Dropdown */
.tag-picker-drop {
    position: absolute;
    right: 0;
    top: 100%;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 8px 0;
    min-width: 160px;
    z-index: 999;
    box-shadow: 0 12px 40px rgba(0,0,0,0.5);
    animation: slideUp 0.15s ease;
}
.tag-picker-title {
    padding: 6px 14px;
    font-size: 11px;
    font-weight: 700;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}
.tag-picker-item {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 7px 14px;
    cursor: pointer;
    font-size: 13px;
    color: var(--text-primary);
    transition: background 0.15s;
}
.tag-picker-item:hover { background: rgba(139,92,246,0.1); }
.tag-picker-item.active { background: rgba(139,92,246,0.08); }
.tag-picker-icon { font-size: 14px; }
.tag-picker-label { flex: 1; }
.tag-picker-check {
    color: var(--accent);
    font-weight: 700;
    font-size: 14px;
}

/* Tag Filter Buttons (in history header) */
.tag-filter-bar {
    display: flex;
    flex-wrap: wrap;
    gap: 5px;
    padding: 8px 16px;
    border-bottom: 1px solid var(--border);
}
.tag-filter-btn {
    display: inline-flex;
    align-items: center;
    gap: 3px;
    padding: 3px 10px;
    border-radius: 8px;
    font-size: 11px;
    font-weight: 600;
    cursor: pointer;
    border: 1px solid var(--border);
    background: transparent;
    color: var(--text-secondary);
    transition: all 0.2s;
    font-family: var(--font);
}
.tag-filter-btn:hover { border-color: var(--accent); color: var(--text-primary); }
.tag-filter-btn.active {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
}

/* ── Tag Picker Dropdown ──────────────── */
.tag-picker-drop {
    position: absolute;
    right: 0;
    top: calc(100% + 4px);
    background: #1a1a2e;
    border: 1px solid rgba(139,92,246,0.3);
    border-radius: 12px;
    padding: 8px 0;
    min-width: 180px;
    z-index: 9000;
    box-shadow: 0 16px 48px rgba(0,0,0,0.7), 0 0 0 1px rgba(0,0,0,0.3);
    animation: slideUp 0.15s ease;
}
[data-theme="light"] .tag-picker-drop {
    background: #ffffff;
    border-color: #e5e7eb;
    box-shadow: 0 12px 40px rgba(0,0,0,0.15);
}
.tag-picker-title {
    padding: 6px 14px 8px;
    font-size: 10px;
    font-weight: 700;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.8px;
    border-bottom: 1px solid var(--border);
    margin-bottom: 4px;
}
.tag-picker-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 14px;
    cursor: pointer;
    font-size: 13px;
    color: var(--text-primary);
    transition: background 0.15s;
}
.tag-picker-item:hover { background: rgba(139,92,246,0.12); }
.tag-picker-item.active { background: rgba(139,92,246,0.08); }
.tag-picker-icon { font-size: 16px; flex-shrink: 0; }
.tag-picker-label { flex: 1; font-weight: 500; }
.tag-picker-check {
    color: var(--accent);
    font-weight: 700;
    font-size: 14px;
}

/* ── Flashcard Dropdown Menu ──────────── */
.fc-dropdown {
    position: relative;
    display: inline-block;
}
.fc-menu {
    position: absolute;
    top: calc(100% + 6px);
    right: 0;
    background: #1a1a2e;
    border: 1px solid rgba(139,92,246,0.3);
    border-radius: 14px;
    padding: 8px;
    min-width: 240px;
    z-index: 100;
    box-shadow: 0 16px 48px rgba(0,0,0,0.7), 0 0 0 1px rgba(0,0,0,0.3);
    animation: slideUp 0.15s ease;
}
[data-theme="light"] .fc-menu {
    background: #ffffff;
    border-color: #e5e7eb;
    box-shadow: 0 12px 40px rgba(0,0,0,0.15);
}
.fc-menu-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 10px 12px;
    border-radius: 10px;
    border: none;
    background: none;
    color: var(--text-primary);
    cursor: pointer;
    width: 100%;
    text-align: left;
    font-family: var(--font);
    transition: background 0.15s;
}
.fc-menu-item:hover { background: rgba(139,92,246,0.12); }
.fc-menu-icon { font-size: 22px; flex-shrink: 0; }
.fc-menu-title {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-primary);
}
.fc-menu-sub {
    font-size: 11px;
    color: var(--text-secondary);
    margin-top: 1px;
}
.fc-menu-divider {
    height: 1px;
    background: var(--border);
    margin: 4px 8px;
}
.fc-study-item { }
.fc-study-item:hover { background: rgba(139,92,246,0.15); }

/* ── Copy Result Link Button ──────────── */
.share-action-result {
    background: linear-gradient(135deg, rgba(16,185,129,0.12), rgba(16,185,129,0.06));
    border-color: rgba(16,185,129,0.3);
    color: #34d399;
}
.share-action-result:hover {
    background: linear-gradient(135deg, rgba(16,185,129,0.2), rgba(16,185,129,0.1));
    border-color: rgba(16,185,129,0.5);
    transform: translateY(-1px);
}

/* ── Chapter Deep Dive Button ──────────── */
.deep-dive-btn {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    margin-top: 8px;
    padding: 4px 12px;
    border-radius: 8px;
    border: 1px solid rgba(139,92,246,0.25);
    background: rgba(139,92,246,0.08);
    color: #a78bfa;
    font-size: 11px;
    font-weight: 600;
    font-family: var(--font);
    cursor: pointer;
    transition: all 0.2s;
    opacity: 0;
}
.topic-item:hover .deep-dive-btn { opacity: 1; }
.deep-dive-btn:hover {
    background: rgba(139,92,246,0.18);
    border-color: rgba(139,92,246,0.5);
    color: #c4b5fd;
    transform: translateY(-1px);
}

/* ── Custom Flashcard Modal ──────────── */
.custom-fc-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.7);
    backdrop-filter: blur(6px);
    z-index: 9500;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
    animation: fadeIn 0.15s ease;
}
.custom-fc-modal {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 18px;
    width: 90vw;
    max-width: 480px;
    max-height: 80vh;
    display: flex;
    flex-direction: column;
    box-shadow: 0 24px 64px rgba(0,0,0,0.6);
    animation: slideUp 0.2s ease;
}
.custom-fc-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 18px 22px;
    border-bottom: 1px solid var(--border);
}
.custom-fc-header h3 { font-size: 16px; font-weight: 700; color: var(--text-primary); margin: 0; }
.custom-fc-close {
    background: none; border: none; color: var(--text-secondary);
    font-size: 24px; cursor: pointer; line-height: 1;
}
.custom-fc-close:hover { color: var(--accent); }
.custom-fc-body {
    padding: 20px 22px;
    overflow-y: auto;
    flex: 1;
}
.custom-fc-label {
    display: block;
    font-size: 12px;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 6px;
    text-transform: uppercase;
    letter-spacing: 0.3px;
}
.custom-fc-input {
    width: 100%;
    padding: 10px 14px;
    border-radius: 10px;
    border: 1px solid var(--border);
    background: var(--bg-main);
    color: var(--text-primary);
    font-family: var(--font);
    font-size: 14px;
    resize: vertical;
    margin-bottom: 14px;
    transition: border-color 0.2s;
}
.custom-fc-input:focus { outline: none; border-color: var(--accent); }
.custom-fc-actions {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 18px;
}
.custom-fc-save {
    padding: 9px 22px;
    border-radius: 10px;
    border: none;
    background: linear-gradient(135deg, var(--accent), #7c3aed);
    color: white;
    font-family: var(--font);
    font-size: 13px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}
.custom-fc-save:hover { transform: translateY(-1px); box-shadow: 0 6px 20px rgba(139,92,246,0.4); }
.custom-fc-count {
    font-size: 12px;
    color: var(--text-secondary);
}
.custom-fc-list {
    border-top: 1px solid var(--border);
    padding-top: 12px;
}
.custom-fc-empty {
    text-align: center;
    color: var(--text-secondary);
    font-size: 13px;
    padding: 16px 0;
    font-style: italic;
}
.custom-fc-item {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 0;
    border-bottom: 1px solid rgba(255,255,255,0.05);
    font-size: 12px;
}
.custom-fc-item-front {
    flex: 1;
    color: var(--text-primary);
    font-weight: 500;
}
.custom-fc-item-back {
    flex: 1;
    color: var(--text-secondary);
}
.custom-fc-item-del {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    font-size: 16px;
    padding: 2px 6px;
    border-radius: 4px;
}
.custom-fc-item-del:hover { color: #ef4444; background: rgba(239,68,68,0.1); }

/* ── Study Statistics ──────────────────── */
.db-study-stats {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
}
.stats-card {
    background: var(--bg-main);
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 18px;
}
.stats-card-wide { grid-column: 1 / -1; }
.stats-card-title {
    font-size: 13px;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 14px;
}
.stats-empty {
    text-align: center;
    color: var(--text-secondary);
    font-size: 12px;
    padding: 20px 0;
    font-style: italic;
}
/* Weekly Bar Chart */
.stats-bar-header {
    display: flex;
    justify-content: space-between;
    font-size: 11px;
    color: var(--text-secondary);
    margin-bottom: 12px;
    padding: 0 4px;
    font-weight: 600;
    gap: 12px;
}
.stats-bar-chart {
    display: flex;
    gap: 6px;
    align-items: flex-end;
    height: 80px;
}
.stats-bar-col {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
}
.stats-bar-track {
    width: 100%;
    height: 60px;
    background: rgba(139,92,246,0.06);
    border-radius: 6px;
    display: flex;
    align-items: flex-end;
    overflow: hidden;
}
.stats-bar-fill {
    width: 100%;
    background: rgba(139,92,246,0.15);
    border-radius: 6px;
    transition: height 0.4s ease;
    min-height: 4px;
}
.stats-bar-fill.active {
    background: linear-gradient(to top, #8b5cf6, #a78bfa);
}
.stats-bar-label {
    font-size: 9px;
    color: var(--text-secondary);
    font-weight: 600;
}
.stats-bar-label.today { color: var(--accent); }
.stats-bar-day {
    font-size: 8px;
    color: var(--text-secondary);
    opacity: 0.6;
}
/* Category Distribution */
.stats-cat-row {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 6px 0;
}
.stats-cat-info {
    min-width: 90px;
    font-size: 12px;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 5px;
}
.stats-cat-icon { font-size: 14px; }
.stats-cat-bar-wrap {
    flex: 1;
    height: 8px;
    background: rgba(255,255,255,0.05);
    border-radius: 4px;
    overflow: hidden;
}
.stats-cat-bar {
    height: 100%;
    border-radius: 4px;
    transition: width 0.5s ease;
}
.stats-cat-pct {
    font-size: 11px;
    color: var(--text-secondary);
    min-width: 55px;
    text-align: right;
}
/* SM-2 Stats */
.stats-sm2-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
}
.stats-sm2-item {
    text-align: center;
    padding: 12px 8px;
    background: rgba(139,92,246,0.04);
    border-radius: 10px;
    border: 1px solid rgba(139,92,246,0.08);
}
.stats-sm2-num {
    font-size: 24px;
    font-weight: 800;
}
.stats-sm2-lbl {
    font-size: 10px;
    color: var(--text-secondary);
    margin-top: 2px;
    font-weight: 500;
}
/* Learning Timeline */
.stats-tl-chart {
    display: flex;
    gap: 4px;
    align-items: flex-end;
    height: 90px;
    padding-bottom: 4px;
}
.stats-tl-col {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 3px;
}
.stats-tl-count {
    font-size: 9px;
    color: var(--accent);
    font-weight: 700;
}
.stats-tl-track {
    width: 100%;
    height: 60px;
    background: rgba(16,185,129,0.06);
    border-radius: 5px;
    display: flex;
    align-items: flex-end;
    overflow: hidden;
}
.stats-tl-fill {
    width: 100%;
    background: linear-gradient(to top, #10b981, #34d399);
    border-radius: 5px;
    transition: height 0.5s ease;
}
.stats-tl-date {
    font-size: 8px;
    color: var(--text-secondary);
    white-space: nowrap;
}
.stats-tl-summary {
    display: flex;
    justify-content: space-around;
    margin-top: 12px;
    padding-top: 10px;
    border-top: 1px solid var(--border);
}
.stats-tl-summary span {
    font-size: 11px;
    color: var(--text-secondary);
    font-weight: 500;
}
@media (max-width: 700px) {
    .db-study-stats { grid-template-columns: 1fr; }
    .stats-sm2-grid { grid-template-columns: repeat(2, 1fr); }
}