/* ==========================================================================
   考点清单 kaodian.css v2 — 移动端优先 · 进度追踪 · 精美大气
   2026 升级版
   ========================================================================== */

/* ===== CSS 变量 ===== */
:root {
    --kd-math: #6366f1;      --kd-math-light: #eef2ff;    --kd-math-dark: #4338ca;   --kd-math-glow: rgba(99,102,241,.14);
    --kd-physics: #059669;   --kd-physics-light: #ecfdf5;  --kd-physics-dark: #047857; --kd-physics-glow: rgba(5,150,105,.14);
    --kd-chemistry: #ea580c; --kd-chem-light: #fff7ed;     --kd-chem-dark: #c2410c;   --kd-chem-glow: rgba(234,88,12,.14);
    --kd-tips: #7c3aed;      --kd-tips-light: #f5f3ff;
    --kd-mistake: #dc2626;   --kd-mistake-light: #fef2f2;
    --kd-success: #16a34a;   --kd-success-light: #f0fdf4;

    --kd-bg: #f8fafc;
    --kd-surface: #ffffff;
    --kd-border: #e2e8f0;
    --kd-text: #1e293b;
    --kd-text-secondary: #64748b;
    --kd-text-muted: #94a3b8;
    --kd-radius: 12px;
    --kd-radius-lg: 18px;
    --kd-radius-xl: 24px;
    --kd-shadow-xs: 0 1px 2px rgba(0,0,0,.04);
    --kd-shadow-sm: 0 1px 3px rgba(0,0,0,.06);
    --kd-shadow: 0 2px 6px rgba(0,0,0,.06), 0 1px 3px rgba(0,0,0,.04);
    --kd-shadow-md: 0 6px 16px rgba(0,0,0,.07);
    --kd-shadow-lg: 0 12px 32px rgba(0,0,0,.08);
    --kd-transition: .28s cubic-bezier(.4,0,.2,1);
}

* { box-sizing: border-box; }

/* ===== 基础布局 ===== */
.kd-main {
    max-width: 860px;
    margin: 0 auto;
    padding: 0 12px 80px;
    background: var(--kd-bg);
    min-height: 100vh;
}

/* ===== 顶部进度条 ===== */
.kd-progress-bar-wrap {
    position: sticky;
    top: 0;
    z-index: 100;
    height: 3px;
    background: transparent;
    margin: 0 -12px;
}
.kd-progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--kd-math), var(--kd-physics), var(--kd-chemistry));
    width: 0%;
    transition: width .35s ease;
    border-radius: 0 2px 2px 0;
    box-shadow: 0 0 8px rgba(99,102,241,.4);
}

/* ===== Hero ===== */
.kd-hero {
    background: linear-gradient(135deg, #0f0a2e 0%, #1e1b4b 25%, #312e81 50%, #4c1d95 75%, #5b21b6 100%);
    border-radius: var(--kd-radius-xl);
    padding: 28px 20px 24px;
    margin: 12px 0 16px;
    text-align: center;
    color: #fff;
    position: relative;
    overflow: hidden;
    box-shadow: 0 20px 50px rgba(99,102,241,.25);
}
.kd-hero::before {
    content: '';
    position: absolute;
    top: -60%; right: -30%;
    width: 360px; height: 360px;
    background: radial-gradient(circle, rgba(255,255,255,.1) 0%, transparent 65%);
    border-radius: 50%;
    pointer-events: none;
    animation: kd-float 8s ease-in-out infinite;
}
.kd-hero::after {
    content: '';
    position: absolute;
    bottom: -50%; left: -25%;
    width: 300px; height: 300px;
    background: radial-gradient(circle, rgba(167,139,250,.15) 0%, transparent 65%);
    border-radius: 50%;
    pointer-events: none;
    animation: kd-float 10s ease-in-out infinite reverse;
}
@keyframes kd-float {
    0%, 100% { transform: translate(0, 0) scale(1); }
    33% { transform: translate(20px, -10px) scale(1.05); }
    66% { transform: translate(-15px, 8px) scale(.96); }
}
.kd-hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    background: rgba(255,255,255,.16);
    backdrop-filter: blur(8px);
    padding: 5px 18px;
    border-radius: 24px;
    font-size: 12px;
    font-weight: 700;
    letter-spacing: 3px;
    margin-bottom: 12px;
    position: relative;
    z-index: 1;
    border: 1px solid rgba(255,255,255,.2);
    animation: kd-pulse-badge 2.5s ease-in-out infinite;
}
@keyframes kd-pulse-badge {
    0%, 100% { box-shadow: 0 0 0 0 rgba(255,255,255,.15); }
    50% { box-shadow: 0 0 0 8px rgba(255,255,255,0); }
}
.kd-hero-badge-dot {
    width: 7px; height: 7px;
    background: #fbbf24;
    border-radius: 50%;
    animation: kd-blink 1.5s ease-in-out infinite;
}
@keyframes kd-blink {
    0%, 100% { opacity: 1; }
    50% { opacity: .3; }
}
.kd-hero-title {
    font-size: 25px;
    font-weight: 900;
    margin: 0 0 8px;
    line-height: 1.3;
    position: relative;
    z-index: 1;
    background: linear-gradient(135deg, #fff, #c4b5fd);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
.kd-hero-sub {
    font-size: 13px;
    opacity: .8;
    margin: 0 0 16px;
    position: relative;
    z-index: 1;
}
.kd-hero-meta {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 6px 20px;
    font-size: 11px;
    opacity: .65;
    position: relative;
    z-index: 1;
}
.kd-hero-strategy { position: relative; z-index: 1; margin-top: 16px; }
.kd-strategy-card {
    display: flex;
    align-items: center;
    gap: 10px;
    background: rgba(255,255,255,.1);
    backdrop-filter: blur(8px);
    border-radius: 14px;
    padding: 12px 16px;
    text-align: left;
    border: 1px solid rgba(255,255,255,.12);
    transition: var(--kd-transition);
}
.kd-strategy-icon { font-size: 30px; flex-shrink: 0; }
.kd-strategy-text { display: flex; flex-direction: column; gap: 3px; }
.kd-strategy-text strong { font-size: 13px; }
.kd-strategy-text span { font-size: 11px; opacity: .75; }

/* ===== Nav 快速导航 ===== */
.kd-nav {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 8px;
    margin-bottom: 16px;
    position: sticky;
    top: 3px;
    z-index: 90;
    background: var(--kd-bg);
    padding: 4px 0;
}
.kd-nav-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 3px;
    padding: 13px 6px;
    border-radius: var(--kd-radius);
    text-decoration: none;
    background: var(--kd-surface);
    box-shadow: var(--kd-shadow-xs);
    transition: var(--kd-transition);
    border: 1.5px solid var(--kd-border);
    position: relative;
    overflow: hidden;
}
.kd-nav-item::after {
    content: '';
    position: absolute;
    bottom: 0; left: 0; right: 0;
    height: 3px;
    background: transparent;
    transition: var(--kd-transition);
}
.kd-nav-item:active { transform: scale(.96); }
.kd-nav-item.active::after,
.kd-nav-math::after { background: var(--kd-math); }
.kd-nav-physics::after { background: var(--kd-physics); }
.kd-nav-chemistry::after { background: var(--kd-chemistry); }
.kd-nav-item.active {
    box-shadow: var(--kd-shadow);
    border-color: transparent;
}
.kd-nav-emoji { font-size: 26px; transition: var(--kd-transition); }
.kd-nav-label { font-size: 14px; font-weight: 700; color: var(--kd-text); }
.kd-nav-desc { font-size: 10px; color: var(--kd-text-secondary); }

/* ===== Subject Section ===== */
.kd-subject {
    margin-bottom: 14px;
    border-radius: var(--kd-radius-lg);
    overflow: hidden;
    box-shadow: var(--kd-shadow-sm);
}
.kd-subject-header {
    padding: 20px 16px 16px;
    position: relative;
    overflow: hidden;
}
.kd-subject-math .kd-subject-header {
    background: linear-gradient(150deg, #eef2ff 0%, #e0e7ff 50%, #c7d2fe 100%);
}
.kd-subject-physics .kd-subject-header {
    background: linear-gradient(150deg, #ecfdf5 0%, #d1fae5 50%, #a7f3d0 100%);
}
.kd-subject-chemistry .kd-subject-header {
    background: linear-gradient(150deg, #fff7ed 0%, #fed7aa 50%, #fdba74 100%);
}
.kd-subject-tips .kd-subject-header {
    background: linear-gradient(150deg, #f5f3ff 0%, #ede9fe 50%, #ddd6fe 100%);
}
.kd-subject-header::after {
    content: '';
    position: absolute;
    top: -30px; right: -20px;
    width: 120px; height: 120px;
    border-radius: 50%;
    opacity: .07;
    pointer-events: none;
}
.kd-subject-math .kd-subject-header::after { background: var(--kd-math); }
.kd-subject-physics .kd-subject-header::after { background: var(--kd-physics); }
.kd-subject-chemistry .kd-subject-header::after { background: var(--kd-chemistry); }
.kd-subject-badge {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    padding: 4px 14px;
    border-radius: 14px;
    font-size: 11px;
    font-weight: 700;
    letter-spacing: 1.5px;
    margin-bottom: 8px;
}
.kd-badge-math { background: var(--kd-math); color: #fff; }
.kd-badge-physics { background: var(--kd-physics); color: #fff; }
.kd-badge-chemistry { background: var(--kd-chemistry); color: #fff; }
.kd-badge-tips { background: var(--kd-tips); color: #fff; }
.kd-subject-title {
    font-size: 19px;
    font-weight: 800;
    margin: 0 0 6px;
    color: var(--kd-text);
}
.kd-subject-emoji { font-size: 22px; }
.kd-subject-desc {
    font-size: 12px;
    color: var(--kd-text-secondary);
    margin: 0;
    line-height: 1.5;
}
/* Subject stats row */
.kd-subject-stats {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 10px;
}
.kd-stat-item {
    display: flex;
    align-items: center;
    gap: 4px;
    font-size: 11px;
    color: var(--kd-text-secondary);
    background: rgba(255,255,255,.6);
    padding: 3px 10px;
    border-radius: 10px;
    backdrop-filter: blur(4px);
}
.kd-stat-dot {
    width: 6px; height: 6px;
    border-radius: 50%;
}

/* ===== Part 折叠面板 ===== */
.kd-part {
    background: var(--kd-surface);
    border-bottom: 1px solid var(--kd-border);
    overflow: hidden;
}
.kd-part:last-child { border-bottom: none; border-radius: 0 0 var(--kd-radius-lg) var(--kd-radius-lg); }
.kd-part-header {
    width: 100%;
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 13px 14px;
    background: none;
    border: none;
    cursor: pointer;
    text-align: left;
    font-family: inherit;
    -webkit-tap-highlight-color: transparent;
    min-height: 48px;
    transition: background var(--kd-transition);
    user-select: none;
}
.kd-part-header:active { background: rgba(0,0,0,.015); }
.kd-part-header:hover { background: rgba(0,0,0,.008); }
.kd-part-label {
    font-size: 10px;
    font-weight: 800;
    padding: 3px 9px;
    border-radius: 7px;
    white-space: nowrap;
    flex-shrink: 0;
    letter-spacing: .5px;
}
.kd-label-easy { background: #dcfce7; color: #166534; }
.kd-label-mid { background: #fef3c7; color: #92400e; }
.kd-label-hard { background: #fee2e2; color: #991b1b; }
.kd-label-physics { background: #d1fae5; color: #047857; }
.kd-label-chemistry { background: #fed7aa; color: #9a3412; }
.kd-label-strategy { background: #ede9fe; color: #6d28d9; }
.kd-part-title {
    font-size: 13px;
    font-weight: 700;
    color: var(--kd-text);
    flex: 1;
}
.kd-part-title small {
    font-size: 11px;
    font-weight: 400;
    color: var(--kd-text-secondary);
}
.kd-part-meta {
    font-size: 10px;
    color: var(--kd-text-muted);
    margin-left: auto;
    flex-shrink: 0;
}
.kd-part-arrow {
    font-size: 11px;
    color: var(--kd-text-secondary);
    transition: transform var(--kd-transition);
    flex-shrink: 0;
    width: 20px; text-align: center;
}
.kd-part.open .kd-part-arrow { transform: rotate(180deg); }
.kd-part-body {
    max-height: 0;
    overflow: hidden;
    transition: max-height .45s ease, padding .3s ease;
}
.kd-part-body { padding: 0 12px; }
.kd-part.open .kd-part-body {
    max-height: 8000px;
    padding: 0 12px 10px;
}

/* ===== section-divider ===== */
.kd-section-divider {
    display: flex;
    align-items: center;
    gap: 10px;
    margin: 10px 0 8px;
    opacity: .5;
}
.kd-section-divider::before,
.kd-section-divider::after {
    content: '';
    flex: 1;
    height: 1px;
    background: var(--kd-border);
}
.kd-section-divider span {
    font-size: 10px;
    color: var(--kd-text-muted);
    letter-spacing: 1px;
}

/* ===== Card ===== */
.kd-card {
    background: var(--kd-surface);
    border: 1px solid var(--kd-border);
    border-radius: var(--kd-radius);
    padding: 14px;
    margin-bottom: 8px;
    box-shadow: var(--kd-shadow-xs);
    transition: box-shadow var(--kd-transition), border-color var(--kd-transition);
    position: relative;
}
.kd-card:last-child { margin-bottom: 0; }
.kd-card:hover { box-shadow: var(--kd-shadow); }
.kd-card-title {
    font-size: 14px;
    font-weight: 700;
    color: var(--kd-text);
    margin: 0 0 10px;
    display: flex;
    align-items: center;
    gap: 8px;
}
.kd-dot {
    width: 9px; height: 9px;
    border-radius: 50%;
    flex-shrink: 0;
    box-shadow: 0 0 6px currentColor;
}
.kd-dot-math { background: var(--kd-math); color: var(--kd-math); }
.kd-dot-physics { background: var(--kd-physics); color: var(--kd-physics); }
.kd-dot-chemistry { background: var(--kd-chemistry); color: var(--kd-chemistry); }

/* Checkbox on cards */
.kd-card-check {
    position: absolute;
    top: 10px; right: 10px;
    width: 22px; height: 22px;
    border-radius: 50%;
    border: 2px solid #d1d5db;
    background: var(--kd-surface);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--kd-transition);
    flex-shrink: 0;
    -webkit-tap-highlight-color: transparent;
}
.kd-card-check:hover { border-color: var(--kd-math); }
.kd-card-check.checked {
    background: var(--kd-success);
    border-color: var(--kd-success);
}
.kd-card-check.checked::after {
    content: '✓';
    color: #fff;
    font-size: 12px;
    font-weight: 700;
}
.kd-card.checked {
    border-color: #bbf7d0;
    background: #f9fefb;
}

/* ===== Tag List ===== */
.kd-tag-list {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}
.kd-tag {
    display: inline-flex;
    align-items: center;
    padding: 5px 11px;
    border-radius: 20px;
    font-size: 11.5px;
    font-weight: 500;
    background: #f1f5f9;
    color: #475569;
    line-height: 1.45;
    border: 1px solid #e2e8f0;
    transition: var(--kd-transition);
}
.kd-tag:hover { border-color: #cbd5e1; }
.kd-tag-lg { font-size: 13px; padding: 7px 14px; font-weight: 600; letter-spacing: .5px; }
.kd-tag-xl { font-size: 14px; padding: 8px 16px; font-weight: 700; }

/* Color tags */
.kd-tag-black { background: #1e293b; color: #fff; border-color: #1e293b; }
.kd-tag-red { background: #fef2f2; color: #991b1b; border-color: #fecaca; }
.kd-tag-blue { background: #eff6ff; color: #1e40af; border-color: #bfdbfe; }
.kd-tag-yellow { background: #fffbeb; color: #92400e; border-color: #fde68a; }
.kd-tag-green { background: #ecfdf5; color: #065f46; border-color: #a7f3d0; }
.kd-tag-white { background: #f8fafc; color: #334155; border-color: #cbd5e1; }
.kd-tag-purple { background: #f5f3ff; color: #6d28d9; border-color: #d8b4fe; }
.kd-tag-orange { background: #fff7ed; color: #c2410c; border-color: #fed7aa; }

/* ===== Tip Box ===== */
.kd-tip {
    margin-top: 10px;
    padding: 9px 12px;
    border-radius: 10px;
    font-size: 11.5px;
    line-height: 1.55;
    color: #6d28d9;
    background: #f5f3ff;
    border-left: 3px solid #a78bfa;
}

/* ===== Mistake Box ===== */
.kd-mistake {
    margin-top: 8px;
    padding: 9px 12px;
    border-radius: 10px;
    font-size: 11.5px;
    line-height: 1.55;
    color: #991b1b;
    background: #fef2f2;
    border-left: 3px solid #f87171;
}
.kd-mistake strong { color: #dc2626; }

/* ===== Mnemonic Box ===== */
.kd-mnemonic {
    margin-top: 8px;
    padding: 9px 12px;
    border-radius: 10px;
    font-size: 11.5px;
    line-height: 1.55;
    color: #1e40af;
    background: #eff6ff;
    border-left: 3px solid #60a5fa;
}

/* ===== Card Highlight ===== */
.kd-card-highlight {
    background: linear-gradient(135deg, #fffbeb, #fef3c7);
    border-color: #fde68a;
}

/* ===== Ability Grid ===== */
.kd-ability-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 6px;
}
.kd-ability-item {
    padding: 9px 10px;
    border-radius: 10px;
    font-size: 12px;
    font-weight: 600;
    background: rgba(255,255,255,.7);
    border: 1px solid #fde68a;
    text-align: center;
    transition: var(--kd-transition);
}

/* ===== Equation List ===== */
.kd-eq-list {
    display: flex;
    flex-direction: column;
    gap: 6px;
}
.kd-eq-item {
    display: flex;
    align-items: flex-start;
    gap: 8px;
    padding: 9px 12px;
    border-radius: 10px;
    background: #fffbeb;
    border: 1px solid #fde68a;
    font-size: 12px;
    line-height: 1.65;
    color: #451a03;
}
.kd-eq-num {
    flex-shrink: 0;
    width: 24px; height: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: #f59e0b;
    color: #fff;
    border-radius: 50%;
    font-size: 11px;
    font-weight: 700;
    box-shadow: 0 2px 6px rgba(245,158,11,.3);
}
.kd-eq { font-weight: 600; }
.kd-eq-simple { background: #fefce8; border-color: #fef08a; }

/* ===== Tips Grid ===== */
.kd-tips-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 8px;
    padding: 12px;
    background: var(--kd-surface);
    border-radius: 0 0 var(--kd-radius-lg) var(--kd-radius-lg);
}
.kd-tip-card {
    padding: 16px;
    border-radius: var(--kd-radius);
    background: #faf5ff;
    border: 1px solid #ede9fe;
    transition: var(--kd-transition);
}
.kd-tip-card:hover { box-shadow: var(--kd-shadow-sm); }
.kd-tip-card-icon { font-size: 32px; margin-bottom: 8px; }
.kd-tip-card h4 {
    font-size: 14px; font-weight: 700;
    margin: 0 0 6px;
    color: #6d28d9;
}
.kd-tip-card p {
    font-size: 12px; color: #6b7280;
    margin: 0; line-height: 1.65;
}

/* ===== Strategy Grid (new sections) ===== */
.kd-strategy-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 8px;
}
.kd-strategy-block {
    padding: 16px;
    border-radius: var(--kd-radius);
    background: var(--kd-surface);
    border: 1px solid var(--kd-border);
    box-shadow: var(--kd-shadow-xs);
}
.kd-strategy-block h4 {
    font-size: 14px; font-weight: 700;
    margin: 0 0 8px;
    display: flex; align-items: center; gap: 6px;
}
.kd-strategy-block ul {
    margin: 0; padding: 0 0 0 18px;
    font-size: 12px; color: var(--kd-text-secondary);
    line-height: 1.8;
}
.kd-strategy-block li { margin-bottom: 2px; }
.kd-strategy-block li strong { color: var(--kd-text); }

/* ===== Time Table ===== */
.kd-time-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 11px;
    margin-top: 8px;
}
.kd-time-table th {
    padding: 8px 10px;
    background: #f1f5f9;
    font-weight: 700;
    text-align: left;
    font-size: 11px;
    color: var(--kd-text);
    border-radius: 6px 6px 0 0;
}
.kd-time-table td {
    padding: 7px 10px;
    border-bottom: 1px solid var(--kd-border);
    color: var(--kd-text-secondary);
}
.kd-time-table tr:last-child td { border-bottom: none; }
.kd-time-table .kd-time-bar {
    display: inline-block;
    height: 8px;
    border-radius: 4px;
    margin-right: 6px;
    vertical-align: middle;
}

/* ===== Footer ===== */
.kd-footer {
    text-align: center;
    padding: 28px 16px;
    color: var(--kd-text-secondary);
    font-size: 12px;
}
.kd-footer p { margin: 4px 0; }
.kd-footer-note {
    font-size: 14px;
    font-weight: 700;
    background: linear-gradient(135deg, var(--kd-math), var(--kd-tips));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* ===== Floating Tools ===== */
.kd-float-tools {
    position: fixed;
    bottom: 24px;
    right: 16px;
    z-index: 200;
    display: flex;
    flex-direction: column;
    gap: 8px;
}
.kd-float-btn {
    width: 44px; height: 44px;
    border-radius: 50%;
    border: none;
    background: var(--kd-surface);
    box-shadow: var(--kd-shadow-md);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    transition: var(--kd-transition);
    -webkit-tap-highlight-color: transparent;
    border: 1px solid var(--kd-border);
    position: relative;
}
.kd-float-btn:active { transform: scale(.9); }
.kd-float-btn:hover { box-shadow: var(--kd-shadow-lg); }
.kd-float-btn-back { opacity: 0; pointer-events: none; transition: opacity .3s, transform var(--kd-transition); }
.kd-float-btn-back.visible { opacity: 1; pointer-events: auto; }

/* Progress badge */
.kd-progress-badge {
    position: absolute;
    top: -4px; right: -4px;
    width: 20px; height: 20px;
    border-radius: 50%;
    background: var(--kd-success);
    color: #fff;
    font-size: 10px;
    font-weight: 700;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 2px 6px rgba(22,163,74,.3);
}

/* Toast */
.kd-toast {
    position: fixed;
    bottom: 100px;
    left: 50%;
    transform: translateX(-50%);
    background: #1e293b;
    color: #fff;
    padding: 10px 20px;
    border-radius: 20px;
    font-size: 13px;
    font-weight: 600;
    z-index: 300;
    opacity: 0;
    transition: opacity .3s, transform .3s;
    pointer-events: none;
    box-shadow: 0 8px 24px rgba(0,0,0,.2);
}
.kd-toast.show {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
}
.kd-toast.hide {
    opacity: 0;
    transform: translateX(-50%) translateY(20px);
}

/* ===== Scroll Spy Highlight ===== */
.kd-nav-item.active-scroll {
    box-shadow: var(--kd-shadow-md);
    transform: translateY(-2px);
}

/* ===== Responsive: 平板 ===== */
@media (min-width: 600px) {
    .kd-main { padding: 0 16px 80px; }
    .kd-hero { padding: 36px 32px 30px; border-radius: var(--kd-radius-xl); }
    .kd-hero-title { font-size: 30px; }
    .kd-hero-sub { font-size: 14px; }
    .kd-nav { gap: 10px; position: static; background: transparent; padding: 0; }
    .kd-nav-item { padding: 18px 12px; }
    .kd-nav-emoji { font-size: 30px; }
    .kd-nav-label { font-size: 16px; }
    .kd-subject-title { font-size: 20px; }
    .kd-tips-grid { grid-template-columns: repeat(2, 1fr); }
    .kd-strategy-grid { grid-template-columns: repeat(2, 1fr); }
    .kd-ability-grid { grid-template-columns: repeat(3, 1fr); }
    .kd-part-title { font-size: 14px; }
    .kd-card-title { font-size: 15px; }
    .kd-tag { font-size: 12px; }
    .kd-eq-item { font-size: 13px; }
    .kd-card-check { width: 26px; height: 26px; }
    .kd-float-btn { width: 48px; height: 48px; font-size: 20px; }
}

/* ===== Responsive: 桌面 ===== */
@media (min-width: 768px) {
    .kd-main { padding: 0 24px 100px; }
    .kd-hero { padding: 44px 40px 36px; }
    .kd-hero-title { font-size: 34px; }
    .kd-tips-grid { grid-template-columns: repeat(4, 1fr); }
    .kd-float-tools { right: calc(50% - 430px - 64px); bottom: 32px; }
}

/* Desktop hover only */
@media (hover: hover) {
    .kd-nav-item:hover {
        transform: translateY(-2px);
        box-shadow: var(--kd-shadow);
    }
    .kd-card:hover { border-color: #cbd5e1; }
}

/* ===== 暗色模式 ===== */
@media (prefers-color-scheme: dark) {
    :root {
        --kd-bg: #0b1121;
        --kd-surface: #1a2332;
        --kd-border: #2d3a4a;
        --kd-text: #e2e8f0;
        --kd-text-secondary: #94a3b8;
        --kd-text-muted: #64748b;
        --kd-shadow-xs: 0 1px 2px rgba(0,0,0,.25);
        --kd-shadow-sm: 0 1px 3px rgba(0,0,0,.3);
        --kd-shadow: 0 2px 6px rgba(0,0,0,.35);
        --kd-shadow-md: 0 6px 16px rgba(0,0,0,.4);
        --kd-shadow-lg: 0 12px 32px rgba(0,0,0,.5);
    }
    .kd-subject-math .kd-subject-header { background: linear-gradient(150deg, #1e1b4b, #312e81, #3730a3); }
    .kd-subject-physics .kd-subject-header { background: linear-gradient(150deg, #022c22, #064e3b, #065f46); }
    .kd-subject-chemistry .kd-subject-header { background: linear-gradient(150deg, #431407, #7c2d12, #9a3412); }
    .kd-subject-tips .kd-subject-header { background: linear-gradient(150deg, #2e1065, #4c1d95, #5b21b6); }
    .kd-subject-title { color: #e0e7ff; }
    .kd-subject-math .kd-subject-title { color: #e0e7ff; }
    .kd-subject-physics .kd-subject-title { color: #d1fae5; }
    .kd-subject-chemistry .kd-subject-title { color: #fed7aa; }
    .kd-subject-tips .kd-subject-title { color: #ede9fe; }
    .kd-subject-desc { color: rgba(255,255,255,.6); }
    .kd-part-header:active { background: rgba(255,255,255,.03); }
    .kd-part-title { color: var(--kd-text); }
    .kd-tag { background: #2d3a4a; color: #cbd5e1; border-color: #3d4f64; }
    .kd-tag-black { background: #f1f5f9; color: #0f172a; border-color: #f1f5f9; }
    .kd-tag-red { background: #450a0a; color: #fca5a5; border-color: #7f1d1d; }
    .kd-tag-blue { background: #172554; color: #93c5fd; border-color: #1e3a5f; }
    .kd-tag-yellow { background: #451a03; color: #fcd34d; border-color: #78350f; }
    .kd-tag-green { background: #022c22; color: #6ee7b7; border-color: #064e3b; }
    .kd-tag-white { background: #1e293b; color: #cbd5e1; border-color: #475569; }
    .kd-tag-purple { background: #1e1b4b; color: #c4b5fd; border-color: #4c1d95; }
    .kd-tag-orange { background: #431407; color: #fdba74; border-color: #9a3412; }
    .kd-tip { background: #1e1b4b; color: #c4b5fd; border-color: #6d28d9; }
    .kd-mistake { background: #450a0a; color: #fca5a5; border-color: #dc2626; }
    .kd-mnemonic { background: #172554; color: #93c5fd; border-color: #3b82f6; }
    .kd-card-highlight { background: #451a03; border-color: #78350f; }
    .kd-ability-item { background: rgba(255,255,255,.04); border-color: #78350f; color: #fcd34d; }
    .kd-eq-item { background: #451a03; border-color: #78350f; color: #fed7aa; }
    .kd-eq-simple { background: #422006; border-color: #78350f; }
    .kd-tip-card { background: #1e1b4b; border-color: #312e81; }
    .kd-tip-card p { color: #a5b4fc; }
    .kd-nav-item { background: var(--kd-surface); }
    .kd-nav-label { color: var(--kd-text); }
    .kd-card { background: var(--kd-surface); }
    .kd-card-check { background: var(--kd-surface); border-color: #4b5563; }
    .kd-card.checked { background: #022c22; border-color: #064e3b; }
    .kd-strategy-block { background: var(--kd-surface); }
    .kd-stat-item { background: rgba(255,255,255,.06); }
    .kd-time-table th { background: #1e293b; color: var(--kd-text); }
    .kd-float-btn { background: #1e293b; border-color: #334155; }
    .kd-section-divider::before,
    .kd-section-divider::after { background: #334155; }
}

/* Animations */
@keyframes kd-fadeInUp {
    from { opacity: 0; transform: translateY(16px); }
    to { opacity: 1; transform: translateY(0); }
}
.kd-animate-in {
    animation: kd-fadeInUp .45s ease forwards;
}