/* ===========================================
   高中数学题库 — Apple Education Style
   Clean · Airy · Minimal · Refined
   =========================================== */

/* === Design Tokens === */
:root {
    --bg: #f6f8fc;
    --bg-alt: #eef2f8;
    --surface: #ffffff;
    --surface-hover: #f8fafc;
    --text: #1e293b;
    --text-secondary: #64748b;
    --text-tertiary: #94a3b8;
    --border: #e8ecf1;
    --border-light: #f1f4f8;
    --accent: #3b82f6;
    --accent-hover: #2563eb;
    --accent-soft: #eff6ff;
    --accent-gradient: linear-gradient(135deg, #3b82f6, #6366f1);
    --red: #ef4444;
    --red-soft: #fef2f2;
    --green: #10b981;
    --green-soft: #ecfdf5;
    --amber: #f59e0b;
    --amber-soft: #fffbeb;
    --purple: #8b5cf6;
    --purple-soft: #f5f3ff;
    --radius-sm: 10px;
    --radius: 16px;
    --radius-lg: 20px;
    --radius-xl: 24px;
    --shadow-xs: 0 1px 2px rgba(15,23,42,0.04);
    --shadow-sm: 0 1px 3px rgba(15,23,42,0.04), 0 1px 2px rgba(15,23,42,0.03);
    --shadow: 0 4px 12px rgba(15,23,42,0.04), 0 1px 3px rgba(15,23,42,0.03);
    --shadow-lg: 0 10px 30px rgba(15,23,42,0.06), 0 2px 8px rgba(15,23,42,0.03);
    --shadow-xl: 0 20px 50px rgba(15,23,42,0.08);
    --font: "PingFang SC", "HarmonyOS Sans", "MiSans", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    --transition: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

/* === Reset === */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    line-height: 1.7;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* === App Layout === */
.app-layout { display: flex; min-height: 100vh; }

/* === Sidebar === */
.sidebar {
    position: fixed;
    top: 0; left: 0; bottom: 0;
    width: 240px;
    background: rgba(255,255,255,0.85);
    backdrop-filter: blur(20px) saturate(180%);
    -webkit-backdrop-filter: blur(20px) saturate(180%);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    padding: 20px 14px 16px;
    z-index: 100;
    overflow-y: auto;
}

.sidebar-brand {
    display: flex;
    align-items: center;
    gap: 11px;
    padding: 6px 8px 20px;
    border-bottom: 1px solid var(--border-light);
    margin-bottom: 12px;
}

.brand-icon {
    width: 36px; height: 36px;
    background: var(--accent-gradient);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.brand-title {
    font-size: 15px;
    font-weight: 700;
    color: var(--text);
    letter-spacing: -0.01em;
    line-height: 1.3;
}

.brand-subtitle {
    font-size: 11px;
    color: var(--text-tertiary);
    font-weight: 500;
    letter-spacing: 0.02em;
}

.sidebar-nav {
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.sidebar-link {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 9px 12px;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
    text-decoration: none;
    transition: all var(--transition);
    cursor: pointer;
    border: none;
    background: transparent;
    width: 100%;
    font-family: var(--font);
    letter-spacing: -0.01em;
}

.sidebar-link:hover { background: var(--surface-hover); color: var(--text); }
.sidebar-link.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.sidebar-link svg { flex-shrink: 0; opacity: 0.7; transition: opacity var(--transition); }
.sidebar-link.active svg { opacity: 1; }
.sidebar-link:hover svg { opacity: 0.9; }

.sidebar-spacer { flex: 1; }
.sidebar-actions { display: flex; flex-direction: column; gap: 2px; border-top: 1px solid var(--border-light); padding-top: 10px; margin-top: 8px; }

/* === Main Content === */
.main-content {
    margin-left: 240px;
    flex: 1;
    padding: 32px 40px 60px;
    max-width: 1100px;
    width: 100%;
}

/* === Hero Section === */
.page-hero {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: 32px;
    margin-bottom: 32px;
}

.page-hero-left { flex: 1; }

.page-hero-left h2 {
    font-size: 28px;
    font-weight: 700;
    letter-spacing: -0.02em;
    margin-bottom: 4px;
    color: var(--text);
}

.page-hero-left .hero-subtitle {
    font-size: 14px;
    color: var(--text-secondary);
    margin-bottom: 20px;
}

/* Hero stat card (iOS widget style) */
.hero-stat {
    background: rgba(255,255,255,0.7);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 20px 24px;
    min-width: 160px;
    text-align: center;
    box-shadow: var(--shadow-sm);
}

.hero-stat-value {
    font-size: 36px;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1;
    margin-bottom: 4px;
}

.hero-stat-label {
    font-size: 12px;
    color: var(--text-secondary);
    font-weight: 500;
}

/* === Search === */
.search-row { margin-bottom: 0; }

.search-box {
    position: relative;
    width: 100%;
}

.search-box input,
.search-row input {
    width: 100%;
    height: 52px;
    padding: 0 20px 0 48px;
    border: 1px solid var(--border);
    border-radius: 16px;
    background: var(--surface);
    font-family: var(--font);
    font-size: 15px;
    color: var(--text);
    transition: all var(--transition);
    box-shadow: var(--shadow-xs);
}

.search-row input { height: 48px; padding: 0 16px; border-radius: 14px; }

.search-box input::placeholder,
.search-row input::placeholder { color: var(--text-tertiary); }

.search-box input:focus,
.search-row input:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 4px rgba(59,130,246,0.08);
}

.search-box .search-icon {
    position: absolute;
    left: 16px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-tertiary);
    pointer-events: none;
}

/* === Hero Mascot === */
.hero-mascot {
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0.85;
    animation: float 4s ease-in-out infinite;
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-8px); }
}

/* === Filters (Chapter Cards) === */
.filters {
    background: transparent;
    border-radius: 0;
    box-shadow: none;
    padding: 0;
    margin-bottom: 24px;
    border: none;
}

.filter-row {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 8px;
    padding: 4px 0;
}

.filter-label {
    font-size: 12px;
    color: var(--text-tertiary);
    font-weight: 600;
    letter-spacing: 0.04em;
    text-transform: uppercase;
    margin-right: 4px;
}

.filter-btn {
    background: var(--surface);
    border: 1px solid var(--border);
    color: var(--text-secondary);
    font-family: var(--font);
    font-size: 13px;
    font-weight: 500;
    padding: 7px 16px;
    border-radius: 10px;
    cursor: pointer;
    transition: all var(--transition);
}

.filter-btn:hover {
    background: var(--surface-hover);
    border-color: #d0d5dd;
    transform: translateY(-1px);
}

.filter-btn.active {
    background: var(--accent-gradient);
    border-color: transparent;
    color: white;
    box-shadow: 0 2px 8px rgba(59,130,246,0.25);
}

/* === Toolbar === */
.toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    gap: 12px;
}

.toolbar-admin { display: flex; gap: 8px; }

/* === Results Count === */
.results-count {
    font-size: 12px;
    color: var(--text-tertiary);
    margin-bottom: 16px;
    font-weight: 500;
    letter-spacing: 0.02em;
}

/* === Problem Cards === */
.problem-card {
    background: var(--surface);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    border: 1px solid var(--border-light);
    padding: 24px 28px;
    margin-bottom: 16px;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

.problem-meta {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 14px;
    flex-wrap: wrap;
}

/* === Tags === */
.tag {
    display: inline-flex;
    align-items: center;
    padding: 3px 10px;
    border-radius: 6px;
    font-size: 11px;
    font-weight: 600;
    letter-spacing: 0.02em;
}

.tag-chapter { background: var(--green-soft); color: #059669; }
.tag-difficulty { background: var(--amber-soft); color: #d97706; }

.problem-title {
    font-size: 17px;
    font-weight: 600;
    margin-bottom: 8px;
    letter-spacing: -0.01em;
    line-height: 1.5;
}

.problem-title a { color: var(--text); text-decoration: none; transition: color var(--transition); }
.problem-title a:hover { color: var(--accent); }

.problem-body { font-size: 14px; line-height: 1.75; color: var(--text-secondary); }
.problem-body p { margin-bottom: 6px; }
.problem-body p:last-child { margin-bottom: 0; }

.problem-solution {
    margin-top: 14px;
    padding-top: 14px;
    border-top: 1px solid var(--border-light);
}

.problem-solution summary {
    cursor: pointer;
    color: var(--accent);
    font-size: 13px;
    font-weight: 500;
    user-select: none;
    transition: color var(--transition);
}

.problem-solution summary:hover { color: var(--accent-hover); }
.problem-solution[open] summary { margin-bottom: 8px; }
.problem-solution p { margin-bottom: 6px; font-size: 13px; color: var(--text-secondary); }

/* === Detail Page === */
.problem-detail { padding: 28px 32px; }
.problem-detail .problem-title { font-size: 22px; margin-bottom: 14px; }
.problem-detail .problem-body { font-size: 15px; }

.solution-detail {
    margin-top: 24px;
    padding-top: 20px;
    border-top: 1px solid var(--border-light);
}

.solution-detail h3 {
    font-size: 13px;
    color: var(--accent);
    font-weight: 600;
    margin-bottom: 10px;
    letter-spacing: 0.03em;
    text-transform: uppercase;
}

.solution-detail p { margin-bottom: 8px; font-size: 14px; }

/* === Buttons === */
.btn {
    font-family: var(--font);
    font-size: 13px;
    font-weight: 600;
    padding: 8px 16px;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: all var(--transition);
    letter-spacing: -0.01em;
    display: inline-flex;
    align-items: center;
    gap: 6px;
}

.btn-primary {
    background: var(--accent-gradient);
    color: white;
    box-shadow: 0 1px 3px rgba(59,130,246,0.2);
}
.btn-primary:hover { box-shadow: 0 4px 12px rgba(59,130,246,0.3); transform: translateY(-1px); }

.btn-secondary {
    background: var(--surface);
    color: var(--text);
    border: 1px solid var(--border);
}
.btn-secondary:hover { background: var(--surface-hover); border-color: #d0d5dd; }

.btn-print { background: var(--surface); color: var(--text-secondary); border: 1px solid var(--border); }
.btn-print:hover { background: var(--surface-hover); }

.btn-cancel { background: transparent; color: var(--text-secondary); }
.btn-cancel:hover { color: var(--text); }

.btn-danger { background: var(--red); color: white; }
.btn-danger:hover { background: #dc2626; }

.btn-edit {
    font-family: var(--font);
    font-size: 11px;
    font-weight: 600;
    padding: 3px 10px;
    background: transparent;
    color: var(--accent);
    border: 1px solid #dbeafe;
    border-radius: 6px;
    cursor: pointer;
    transition: all var(--transition);
    margin-left: auto;
}
.btn-edit:hover { background: var(--accent-soft); border-color: var(--accent); }
.btn-edit-sm { font-size: 10px; padding: 2px 8px; }

.btn-delete {
    font-family: var(--font);
    font-size: 11px;
    font-weight: 600;
    padding: 3px 10px;
    background: transparent;
    color: var(--red);
    border: 1px solid #fecaca;
    border-radius: 6px;
    cursor: pointer;
    transition: all var(--transition);
}
.btn-delete:hover { background: var(--red-soft); border-color: var(--red); }
.btn-delete-sm { font-size: 10px; padding: 2px 8px; }

/* === Back Link === */
.back-link {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 13px;
    margin-bottom: 16px;
    font-weight: 500;
    transition: color var(--transition);
}
.back-link::before { content: "←"; font-size: 14px; }
.back-link:hover { color: var(--accent); }

/* === Page Header === */
.page-header h2 {
    font-size: 24px;
    font-weight: 700;
    letter-spacing: -0.02em;
    margin-bottom: 2px;
}
.page-subtitle { font-size: 13px; color: var(--text-secondary); margin-bottom: 24px; }

/* === Empty State === */
.empty-state {
    text-align: center;
    padding: 60px 20px;
    background: var(--surface);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-light);
    color: var(--text-secondary);
    font-size: 14px;
}

/* === Loading === */
.loading-state { text-align: center; padding: 80px 20px; color: var(--text-tertiary); }
.loading-spinner {
    width: 28px; height: 28px;
    border: 3px solid var(--border);
    border-top-color: var(--accent);
    border-radius: 50%;
    animation: spin 0.6s linear infinite;
    margin: 0 auto 12px;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* === Auth Page === */
.auth-overlay {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 70vh;
    padding: 40px 20px;
}

.auth-card {
    background: var(--surface);
    border-radius: var(--radius-xl);
    border: 1px solid var(--border);
    box-shadow: var(--shadow-lg);
    padding: 44px 40px;
    max-width: 380px;
    width: 100%;
    text-align: center;
}

.auth-card h2 {
    font-size: 22px;
    font-weight: 700;
    letter-spacing: -0.02em;
    margin-bottom: 4px;
}

.auth-subtitle { font-size: 13px; color: var(--text-secondary); margin-bottom: 24px; }

.auth-card input[type="text"],
.auth-card input[type="password"] {
    width: 100%;
    font-family: var(--font);
    font-size: 15px;
    padding: 11px 14px;
    border: 1px solid var(--border);
    border-radius: 12px;
    margin-bottom: 10px;
    transition: all var(--transition);
    background: var(--bg);
}

.auth-card input:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(59,130,246,0.08);
}

.auth-btn {
    width: 100%;
    font-family: var(--font);
    font-size: 15px;
    font-weight: 600;
    padding: 11px 0;
    background: var(--accent-gradient);
    color: white;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    transition: all var(--transition);
    margin-top: 4px;
    box-shadow: 0 1px 3px rgba(59,130,246,0.2);
}

.auth-btn:hover { box-shadow: 0 4px 12px rgba(59,130,246,0.3); transform: translateY(-1px); }
.auth-btn:active { transform: scale(0.98); }

.auth-error {
    color: var(--red);
    font-size: 12px;
    margin-top: 8px;
    display: none;
}
.auth-error.show { display: block; animation: shake 0.3s ease; }
@keyframes shake { 0%,100% { transform: translateX(0); } 25% { transform: translateX(-4px); } 75% { transform: translateX(4px); } }

.auth-switch { margin-top: 16px; font-size: 11px; color: var(--text-tertiary); }

/* === Modal === */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(15,23,42,0.3);
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
    display: flex;
    align-items: flex-start;
    justify-content: center;
    padding: 40px 16px;
    z-index: 1000;
    overflow-y: auto;
}

.modal {
    background: var(--surface);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-xl);
    border: 1px solid var(--border);
    max-width: 620px;
    width: 100%;
    animation: modalIn 0.25s cubic-bezier(0.4,0,0.2,1);
}

.modal-sm { max-width: 380px; }

@keyframes modalIn { from { opacity: 0; transform: translateY(-12px) scale(0.97); } to { opacity: 1; transform: translateY(0) scale(1); } }

.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 22px 26px 0;
}

.modal-header h2 {
    font-size: 19px;
    font-weight: 700;
    letter-spacing: -0.01em;
}

.modal-close {
    background: none;
    border: none;
    font-size: 22px;
    color: var(--text-tertiary);
    cursor: pointer;
    transition: color var(--transition);
}
.modal-close:hover { color: var(--text); }

.modal-body { padding: 18px 26px; }
.modal-footer { display: flex; justify-content: flex-end; gap: 8px; padding: 0 26px 22px; }

/* === Forms === */
.form-row { display: flex; gap: 14px; margin-bottom: 14px; }
.form-group { margin-bottom: 14px; }
.form-group-chapter { flex: 1; }
.form-group-difficulty { flex-shrink: 0; }

.form-label {
    display: block;
    font-size: 12px;
    font-weight: 600;
    color: var(--text);
    margin-bottom: 5px;
    letter-spacing: 0.02em;
}

.form-hint { font-weight: 400; color: var(--text-tertiary); font-size: 11px; }

.form-input {
    width: 100%;
    font-family: var(--font);
    font-size: 14px;
    padding: 9px 12px;
    border: 1px solid var(--border);
    border-radius: 10px;
    transition: all var(--transition);
    background: var(--bg);
}
.form-input:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(59,130,246,0.08);
}

.form-textarea {
    width: 100%;
    font-family: var(--font);
    font-size: 14px;
    line-height: 1.7;
    padding: 10px 12px;
    border: 1px solid var(--border);
    border-radius: 10px;
    resize: vertical;
    transition: all var(--transition);
    background: var(--bg);
}
.form-textarea:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(59,130,246,0.08);
}

.form-textarea-sm { font-family: "SF Mono", "Fira Code", monospace; font-size: 12px; }
.form-error { color: var(--red); font-size: 12px; margin-top: 4px; display: none; }
.form-error.show { display: block; }

/* === Star Picker === */
.star-picker { display: flex; gap: 3px; padding-top: 4px; }
.star-item {
    font-size: 22px; cursor: pointer;
    color: #d1d5db; user-select: none;
    transition: color var(--transition), transform var(--transition);
}
.star-item.active, .star-item:hover { color: var(--amber); }
.star-item:hover { transform: scale(1.15); }

/* === Preview Box === */
.preview-box {
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 16px;
    min-height: 60px;
    font-size: 14px;
    line-height: 1.7;
}
.preview-placeholder { color: var(--text-tertiary); font-style: italic; margin: 0; }
.preview-box p { margin-bottom: 6px; }
.preview-box p:last-child { margin-bottom: 0; }

/* === Source Badge === */
.source-badge {
    display: inline-block;
    padding: 2px 8px;
    border-radius: 5px;
    font-size: 10px;
    font-weight: 600;
    letter-spacing: 0.02em;
}
.source-ref { background: var(--green-soft); color: #059669; border: 1px solid #a7f3d0; }
.source-inline { background: var(--red-soft); color: #dc2626; border: 1px solid #fecaca; }

/* === Figures === */
.problem-figure {
    margin: 16px auto;
    display: flex;
    justify-content: center;
}
.problem-figure svg { width: 100%; max-width: 360px; height: auto; }
.problem-detail .problem-figure svg { max-width: 460px; }

/* === Diagram === */
.diagram .edge { stroke: var(--text); stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; fill: none; }
.diagram .hidden { stroke: var(--text); stroke-width: 2; stroke-linecap: round; stroke-dasharray: 6 4; fill: none; }
.diagram .dashed { stroke: var(--text-secondary); stroke-width: 1.5; stroke-dasharray: 4 3; fill: none; }
.diagram .label { font-size: 17px; font-family: "Times New Roman", "Cambria Math", serif; font-style: italic; fill: var(--text); }
.diagram .label-plain { font-size: 14px; font-family: var(--font); fill: var(--text-secondary); }
.diagram .point { fill: var(--text); }

/* === Assignment Cards === */
.assignment-card-link { text-decoration: none; color: inherit; display: block; }
.assignment-card {
    background: var(--surface);
    border-radius: var(--radius);
    border: 1px solid var(--border-light);
    box-shadow: var(--shadow-xs);
    padding: 18px 24px;
    margin-bottom: 12px;
    transition: all 0.3s cubic-bezier(0.4,0,0.2,1);
}
.assignment-card:hover { box-shadow: var(--shadow); transform: translateY(-1px); }

.assignment-date {
    font-size: 11px;
    color: var(--text-tertiary);
    margin-bottom: 4px;
    font-weight: 500;
    letter-spacing: 0.03em;
}
.assignment-title { font-size: 16px; font-weight: 600; margin-bottom: 4px; letter-spacing: -0.01em; }
.assignment-note { font-size: 13px; color: var(--text-secondary); margin-bottom: 4px; }
.assignment-meta { font-size: 11px; color: var(--text-tertiary); }

.assignment-header {
    background: var(--surface);
    border-radius: var(--radius);
    border: 1px solid var(--border-light);
    box-shadow: var(--shadow-xs);
    padding: 24px 28px;
    margin-bottom: 20px;
}
.assignment-date-large { font-size: 12px; color: var(--text-tertiary); margin-bottom: 4px; font-weight: 500; }
.assignment-header h2 { font-size: 22px; font-weight: 700; letter-spacing: -0.01em; margin-bottom: 6px; }
.assignment-note-large { font-size: 14px; color: var(--text-secondary); }
.assignment-meta-large { font-size: 12px; color: var(--text-tertiary); }

/* === Responsive === */
@media (max-width: 768px) {
    .sidebar {
        width: 100%;
        height: auto;
        position: relative;
        flex-direction: row;
        flex-wrap: wrap;
        padding: 12px 16px;
        gap: 8px;
        align-items: center;
        border-right: none;
        border-bottom: 1px solid var(--border);
    }
    .sidebar-brand { border-bottom: none; margin-bottom: 0; padding-bottom: 0; }
    .sidebar-nav { flex-direction: row; gap: 4px; }
    .sidebar-spacer { display: none; }
    .sidebar-actions { display: none; }
    .brand-subtitle { display: none; }

    .main-content { margin-left: 0; padding: 20px 16px; }
    .page-hero { flex-direction: column; }
    .page-hero-left h2 { font-size: 22px; }
    .form-row { flex-direction: column; gap: 0; }
    .modal { max-width: 100%; margin: 0 8px; }
    .toolbar { flex-direction: column; align-items: stretch; }
}

/* === Print === */
@media print {
    .sidebar, .toolbar, .filters, .search-box, .back-link, .btn-delete, .btn-edit,
    .btn-primary, .btn-secondary, .btn-cancel, .btn-danger, .auth-overlay,
    .modal-overlay, .results-count, .form-error, .problem-solution,
    .solution-detail, .problem-meta, .assignment-header, .source-badge,
    .page-hero, .search-row { display: none !important; }

    .app-layout { display: block; }
    .main-content { margin-left: 0; padding: 0; }
    body { background: white; font-size: 13px; line-height: 1.8; color: #000; }

    .problem-card {
        box-shadow: none; border-radius: 0; border: none; padding: 12px 0;
        margin-bottom: 10px; border-bottom: 1px solid #ddd; page-break-inside: avoid; animation: none;
    }
    .problem-detail { border-bottom: none; }
    .problem-title { font-size: 14px; font-weight: 700; margin-bottom: 6px; }
    .problem-title a { color: #000; text-decoration: none; }
    .problem-body { font-size: 13px; }
    .problem-figure { margin: 10px 0 0 0 !important; display: flex !important; justify-content: flex-start !important; }
    .problem-figure svg, .problem-figure img { max-width: 260px; max-height: 180px; }
    @page { size: A4; margin: 15mm; }
}

/* 目录树删除按钮：hover 显示 */
.folder-item:hover .folder-delete {
    display: inline-block !important;
}
.folder-delete:hover {
    opacity: 1 !important;
    color: #c4554d;
}