:root {
    --forest-950: #0b2419;
    --forest-900: #123524;
    --forest-800: #1a4932;
    --forest-700: #286044;
    --leaf: #5e7f49;
    --kumquat: #ed7c25;
    --kumquat-deep: #c95716;
    --kumquat-soft: #f9dfc4;
    --paper: #f6f0e5;
    --paper-raised: #fffaf1;
    --paper-deep: #e9dfce;
    --ink: #1f2a23;
    --ink-soft: #5f675f;
    --line: #d7cbb8;
    --sky: #317a85;
    --danger: #a84032;
    --sidebar-width: 306px;
    --reading-width: 830px;
    --rail-width: 252px;
    --shadow: 0 18px 48px rgba(40, 48, 33, 0.1);
    --shadow-small: 0 8px 20px rgba(40, 48, 33, 0.08);
    --sans: "Microsoft YaHei UI", "PingFang SC", "Noto Sans CJK SC", sans-serif;
    --serif: "Noto Serif CJK SC", "Source Han Serif SC", "SimSun", serif;
    color-scheme: light;
}

[data-theme="night"] {
    --paper: #132019;
    --paper-raised: #1b2a22;
    --paper-deep: #24362b;
    --ink: #edf2e9;
    --ink-soft: #aebcaf;
    --line: #385043;
    --kumquat-soft: #4a321d;
    --shadow: 0 18px 48px rgba(0, 0, 0, 0.28);
    --shadow-small: 0 8px 20px rgba(0, 0, 0, 0.22);
    color-scheme: dark;
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: 96px;
}

body {
    margin: 0;
    background:
        radial-gradient(circle at 78% 4%, rgba(237, 124, 37, 0.11), transparent 25rem),
        radial-gradient(circle at 45% 85%, rgba(49, 122, 133, 0.07), transparent 30rem),
        var(--paper);
    color: var(--ink);
    font-family: var(--sans);
    font-size: 16px;
    line-height: 1.78;
    text-rendering: optimizeLegibility;
}

body.drawer-open,
body.sidebar-open {
    overflow: hidden;
}

button,
input,
textarea {
    font: inherit;
}

button,
a {
    -webkit-tap-highlight-color: transparent;
}

a {
    color: var(--sky);
    text-decoration-thickness: 1px;
    text-underline-offset: 3px;
}

button {
    color: inherit;
}

svg {
    display: block;
}

.skip-link {
    position: fixed;
    z-index: 1000;
    top: 10px;
    left: 10px;
    padding: 8px 14px;
    border-radius: 6px;
    background: var(--kumquat);
    color: #1c241d;
    font-weight: 800;
    transform: translateY(-150%);
}

.skip-link:focus {
    transform: translateY(0);
}

.ambient {
    position: fixed;
    z-index: -1;
    width: 440px;
    height: 440px;
    border: 1px solid rgba(94, 127, 73, 0.15);
    border-radius: 52% 48% 61% 39%;
    pointer-events: none;
}

.ambient-one {
    right: -260px;
    top: 32%;
    transform: rotate(28deg);
}

.ambient-two {
    left: 22%;
    bottom: -350px;
    transform: rotate(-18deg);
}

.app-shell {
    min-height: 100vh;
}

.sidebar {
    position: fixed;
    z-index: 60;
    inset: 0 auto 0 0;
    display: flex;
    width: var(--sidebar-width);
    flex-direction: column;
    overflow: hidden;
    background:
        linear-gradient(145deg, rgba(255, 255, 255, 0.04), transparent 35%),
        var(--forest-950);
    color: #ecf3e9;
    box-shadow: 10px 0 34px rgba(20, 35, 26, 0.14);
}

.sidebar::after {
    position: absolute;
    right: -42px;
    bottom: -60px;
    width: 210px;
    height: 210px;
    border: 34px solid rgba(237, 124, 37, 0.05);
    border-radius: 50%;
    content: "";
    pointer-events: none;
}

.brand-block {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 24px 22px 17px;
}

.brand {
    display: flex;
    align-items: center;
    gap: 11px;
    color: inherit;
    text-decoration: none;
}

.brand-mark {
    display: grid;
    width: 42px;
    height: 42px;
    place-items: center;
    border: 1px solid rgba(255, 255, 255, 0.15);
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.05);
}

.brand-mark svg {
    width: 31px;
    fill: none;
    stroke: #f5a357;
    stroke-linecap: round;
    stroke-linejoin: round;
    stroke-width: 2.1;
}

.brand strong,
.brand small {
    display: block;
}

.brand strong {
    letter-spacing: 0.08em;
    font-family: var(--serif);
    font-size: 17px;
}

.brand small {
    margin-top: -2px;
    color: rgba(236, 243, 233, 0.55);
    font-size: 8px;
    letter-spacing: 0.22em;
}

.course-progress-card {
    margin: 0 17px 16px;
    padding: 14px 15px 12px;
    border: 1px solid rgba(255, 255, 255, 0.09);
    border-radius: 11px;
    background: rgba(255, 255, 255, 0.045);
}

.progress-copy {
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-size: 12px;
}

.progress-copy span {
    color: rgba(236, 243, 233, 0.68);
}

.progress-copy strong {
    color: #ffb973;
    font-size: 15px;
}

.progress-track {
    height: 5px;
    margin: 9px 0 7px;
    overflow: hidden;
    border-radius: 99px;
    background: rgba(255, 255, 255, 0.11);
}

.progress-track span {
    display: block;
    width: 0;
    height: 100%;
    border-radius: inherit;
    background: linear-gradient(90deg, #ed7c25, #ffc06f);
    transition: width 0.35s ease;
}

.course-progress-card p {
    margin: 0;
    color: rgba(236, 243, 233, 0.5);
    font-size: 10px;
}

.sidebar-search,
.dialog-search {
    display: flex;
    align-items: center;
    gap: 9px;
    border: 1px solid rgba(255, 255, 255, 0.11);
    border-radius: 8px;
}

.sidebar-search {
    margin: 0 17px 15px;
    padding: 8px 10px;
    background: rgba(0, 0, 0, 0.12);
}

.sidebar-search svg,
.dialog-search svg {
    width: 17px;
    fill: none;
    stroke: currentColor;
    stroke-linecap: round;
    stroke-width: 1.8;
}

.sidebar-search svg {
    color: rgba(255, 255, 255, 0.46);
}

.sidebar-search input {
    min-width: 0;
    flex: 1;
    border: 0;
    outline: 0;
    background: transparent;
    color: white;
    font-size: 12px;
}

.sidebar-search input::placeholder {
    color: rgba(255, 255, 255, 0.4);
}

kbd {
    display: inline-flex;
    min-width: 21px;
    min-height: 20px;
    align-items: center;
    justify-content: center;
    padding: 0 5px;
    border: 1px solid var(--line);
    border-bottom-width: 2px;
    border-radius: 4px;
    background: var(--paper-raised);
    color: var(--ink-soft);
    font-family: var(--sans);
    font-size: 10px;
    line-height: 1;
}

.sidebar-search kbd {
    border-color: rgba(255, 255, 255, 0.17);
    background: rgba(255, 255, 255, 0.06);
    color: rgba(255, 255, 255, 0.56);
}

.course-nav {
    position: relative;
    z-index: 1;
    flex: 1;
    overflow-y: auto;
    padding: 0 10px 36px 17px;
    scrollbar-color: rgba(255, 255, 255, 0.18) transparent;
    scrollbar-width: thin;
}

.nav-module {
    margin: 8px 0 18px;
}

.nav-module-title {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 0 7px 6px;
    color: rgba(236, 243, 233, 0.42);
    font-size: 9px;
    font-weight: 800;
    letter-spacing: 0.12em;
    text-transform: uppercase;
}

.nav-module-title::before {
    width: 12px;
    height: 1px;
    background: currentColor;
    content: "";
}

.nav-chapter {
    display: grid;
    grid-template-columns: 25px minmax(0, 1fr) 16px;
    gap: 7px;
    align-items: center;
    width: 100%;
    margin: 2px 0;
    padding: 7px 8px;
    border: 0;
    border-radius: 7px;
    background: transparent;
    color: rgba(236, 243, 233, 0.68);
    cursor: pointer;
    text-align: left;
    transition: background 0.18s ease, color 0.18s ease, transform 0.18s ease;
}

.nav-chapter:hover,
.nav-chapter:focus-visible {
    background: rgba(255, 255, 255, 0.06);
    color: white;
    outline: none;
}

.nav-chapter.active {
    background: rgba(237, 124, 37, 0.15);
    color: #ffb66f;
    transform: translateX(2px);
}

.nav-number {
    color: rgba(255, 255, 255, 0.29);
    font-size: 9px;
    font-variant-numeric: tabular-nums;
}

.nav-chapter.active .nav-number {
    color: #ed7c25;
}

.nav-label {
    overflow: hidden;
    font-size: 11px;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.nav-check {
    display: grid;
    width: 15px;
    height: 15px;
    place-items: center;
    border: 1px solid rgba(255, 255, 255, 0.16);
    border-radius: 50%;
    color: transparent;
    font-size: 9px;
}

.nav-chapter.completed .nav-check {
    border-color: #71a570;
    background: #376f4b;
    color: white;
}

.sidebar-footer {
    position: relative;
    z-index: 1;
    display: flex;
    justify-content: space-between;
    padding: 12px 20px 18px;
    border-top: 1px solid rgba(255, 255, 255, 0.07);
}

.text-button {
    padding: 2px;
    border: 0;
    background: transparent;
    color: rgba(236, 243, 233, 0.66);
    cursor: pointer;
    font-size: 10px;
}

.text-button:hover {
    color: white;
}

.text-button.muted {
    color: rgba(236, 243, 233, 0.35);
}

.page-column {
    min-height: 100vh;
    margin-left: var(--sidebar-width);
}

.topbar {
    position: sticky;
    z-index: 45;
    top: 0;
    display: flex;
    height: 66px;
    align-items: center;
    gap: 14px;
    padding: 0 clamp(18px, 3.2vw, 48px);
    border-bottom: 1px solid color-mix(in srgb, var(--line), transparent 25%);
    background: color-mix(in srgb, var(--paper), transparent 7%);
    backdrop-filter: blur(15px);
}

.icon-button {
    display: inline-grid;
    width: 36px;
    height: 36px;
    flex: 0 0 auto;
    place-items: center;
    border: 1px solid var(--line);
    border-radius: 50%;
    background: var(--paper-raised);
    color: var(--ink);
    cursor: pointer;
    transition: border-color 0.18s ease, transform 0.18s ease, background 0.18s ease;
}

.icon-button:hover {
    border-color: var(--kumquat);
    transform: translateY(-1px);
}

.icon-button svg {
    width: 17px;
    fill: none;
    stroke: currentColor;
    stroke-linecap: round;
    stroke-width: 1.7;
}

.menu-button,
.sidebar-close {
    display: none;
}

.sidebar-close {
    border-color: rgba(255, 255, 255, 0.12);
    background: transparent;
    color: white;
}

.breadcrumb {
    display: flex;
    min-width: 0;
    align-items: center;
    gap: 9px;
    flex: 1;
    font-size: 11px;
}

.breadcrumb span {
    color: var(--ink-soft);
}

.breadcrumb span::after {
    margin-left: 9px;
    color: var(--line);
    content: "/";
}

.breadcrumb strong {
    overflow: hidden;
    font-weight: 650;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.topbar-actions {
    display: flex;
    align-items: center;
    gap: 8px;
}

.dictionary-icon {
    font-family: var(--serif);
    font-size: 14px;
    font-weight: 800;
}

.return-button,
.secondary-button {
    border: 1px solid var(--line);
    border-radius: 7px;
    background: var(--paper-raised);
    cursor: pointer;
}

.return-button {
    padding: 7px 11px;
    color: var(--ink-soft);
    font-size: 11px;
}

.return-button:hover {
    border-color: var(--kumquat);
    color: var(--ink);
}

.reading-line {
    position: fixed;
    z-index: 50;
    top: 65px;
    right: 0;
    left: var(--sidebar-width);
    height: 2px;
    background: transparent;
}

.reading-line span {
    display: block;
    width: 0;
    height: 100%;
    background: linear-gradient(90deg, var(--kumquat), #f3b35a);
    transition: width 0.08s linear;
}

.reader-layout {
    display: grid;
    grid-template-columns: minmax(0, var(--reading-width)) var(--rail-width);
    gap: clamp(28px, 4vw, 58px);
    justify-content: center;
    padding: 64px clamp(30px, 4vw, 68px) 90px;
}

.reader {
    min-width: 0;
    outline: none;
}

.chapter {
    counter-reset: figure table;
}

.chapter-hero {
    position: relative;
    margin-bottom: 42px;
    padding: 34px 38px 32px;
    overflow: hidden;
    border: 1px solid var(--line);
    border-radius: 18px 18px 18px 4px;
    background:
        linear-gradient(130deg, transparent 50%, rgba(237, 124, 37, 0.06)),
        var(--paper-raised);
    box-shadow: var(--shadow);
}

.chapter-hero::after {
    position: absolute;
    right: -20px;
    bottom: -52px;
    width: 155px;
    height: 155px;
    border: 28px solid var(--module-color, var(--kumquat));
    border-radius: 50%;
    content: "";
    opacity: 0.08;
}

.chapter-meta {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 9px;
    margin-bottom: 18px;
    color: var(--ink-soft);
    font-size: 10px;
    letter-spacing: 0.05em;
}

.module-stamp {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 4px 8px;
    border-radius: 4px;
    background: var(--module-color, var(--kumquat));
    color: white;
    font-weight: 800;
    letter-spacing: 0.09em;
}

.chapter-kicker {
    margin: 0 0 6px;
    color: var(--kumquat-deep);
    font-size: 11px;
    font-weight: 800;
    letter-spacing: 0.14em;
}

.chapter-hero h1 {
    max-width: 690px;
    margin: 0;
    font-family: var(--serif);
    font-size: clamp(31px, 4vw, 49px);
    font-weight: 800;
    letter-spacing: -0.035em;
    line-height: 1.18;
}

.chapter-summary {
    max-width: 690px;
    margin: 17px 0 0;
    color: var(--ink-soft);
    font-family: var(--serif);
    font-size: 17px;
    line-height: 1.85;
}

.learning-objectives {
    margin: 0 0 38px;
    padding: 23px 28px;
    border-left: 4px solid var(--module-color, var(--kumquat));
    border-radius: 0 10px 10px 0;
    background: color-mix(in srgb, var(--paper-raised), var(--module-color, var(--kumquat)) 4%);
}

.learning-objectives h2 {
    margin: 0 0 8px !important;
    border: 0 !important;
    font-family: var(--sans) !important;
    font-size: 12px !important;
    letter-spacing: 0.12em;
}

.learning-objectives ul {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 7px 26px;
    margin: 0;
    padding-left: 18px;
    color: var(--ink-soft);
    font-size: 13px;
}

.chapter-body > h2 {
    display: flex;
    align-items: center;
    gap: 13px;
    margin: 58px 0 20px;
    padding-bottom: 11px;
    border-bottom: 1px solid var(--line);
    font-family: var(--serif);
    font-size: 25px;
    line-height: 1.45;
}

.chapter-body > h2::before {
    width: 23px;
    height: 4px;
    flex: 0 0 auto;
    border-radius: 99px;
    background: var(--module-color, var(--kumquat));
    content: "";
}

.chapter-body h3 {
    margin: 34px 0 11px;
    color: var(--ink);
    font-size: 18px;
}

.chapter-body p,
.chapter-body li {
    font-family: var(--serif);
    font-size: 16px;
}

.chapter-body p {
    margin: 0 0 16px;
}

.chapter-body ul,
.chapter-body ol {
    margin: 10px 0 22px;
    padding-left: 27px;
}

.chapter-body li + li {
    margin-top: 7px;
}

.chapter-body strong {
    color: color-mix(in srgb, var(--ink), var(--kumquat-deep) 18%);
}

.lead-paragraph::first-letter {
    float: left;
    margin: 9px 8px 0 0;
    color: var(--module-color, var(--kumquat));
    font-family: var(--serif);
    font-size: 52px;
    font-weight: 800;
    line-height: 0.76;
}

.term {
    position: relative;
    display: inline;
    padding: 0 2px;
    border: 0;
    border-bottom: 1px dotted var(--kumquat-deep);
    background: transparent;
    color: inherit;
    cursor: help;
    font-family: inherit;
    font-size: inherit;
    font-weight: 700;
}

.term::after {
    margin-left: 2px;
    color: var(--kumquat-deep);
    content: "°";
    font-family: var(--sans);
    font-size: 10px;
    vertical-align: super;
}

.xref {
    display: inline;
    padding: 0;
    border: 0;
    border-bottom: 1px solid currentColor;
    background: transparent;
    color: var(--sky);
    cursor: pointer;
    font-family: inherit;
    font-size: inherit;
}

.xref::after {
    margin-left: 3px;
    content: "↗";
    font-family: var(--sans);
    font-size: 10px;
}

.formula-card,
.callout,
.worked-example,
.project-card,
.knowledge-check,
.source-panel,
.lab-card,
.d2l-license-card,
.official-doc-card {
    margin: 25px 0;
    border-radius: 11px;
}

.official-doc-card {
    position: relative;
    overflow: hidden;
    padding: 29px 31px 26px;
    border: 1px solid color-mix(in srgb, #76509b, var(--line) 52%);
    background:
        linear-gradient(90deg, transparent 0 96%, color-mix(in srgb, #76509b, transparent 82%) 96%),
        linear-gradient(138deg, color-mix(in srgb, var(--paper-raised), #76509b 8%), var(--paper-raised) 62%);
    box-shadow: inset 6px 0 0 #76509b;
}

.official-doc-card::after {
    position: absolute;
    right: 24px;
    top: 22px;
    width: 74px;
    height: 74px;
    border: 1px dashed color-mix(in srgb, #76509b, transparent 48%);
    border-radius: 50%;
    content: "译";
    color: color-mix(in srgb, #76509b, transparent 38%);
    font-family: var(--serif);
    font-size: 35px;
    line-height: 72px;
    text-align: center;
    transform: rotate(-8deg);
}

.official-doc-card .official-stamp {
    display: inline-flex;
    margin-bottom: 12px;
    padding: 5px 9px;
    border: 1px solid color-mix(in srgb, #76509b, var(--line) 45%);
    border-radius: 999px;
    color: #76509b;
    font-family: var(--sans);
    font-size: 9px;
    font-weight: 850;
    letter-spacing: 0.14em;
}

.official-doc-card h2 {
    position: relative;
    z-index: 1;
    max-width: 780px;
    margin: 0 90px 10px 0;
    color: var(--ink);
    font-size: clamp(24px, 3.1vw, 38px);
    line-height: 1.08;
}

.official-doc-card p:last-child {
    position: relative;
    z-index: 1;
    max-width: 780px;
    margin-bottom: 0;
}

.chapter-figure {
    display: block;
    width: 100%;
    height: auto;
    margin: 28px 0;
    border: 1px solid var(--line);
    border-radius: 15px;
    background: #eee5cf;
    box-shadow: var(--shadow-small);
}

.model-route-strip {
    display: flex;
    align-items: center;
    gap: 10px;
    margin: 24px 0;
    padding: 15px 17px;
    overflow-x: auto;
    border: 1px solid color-mix(in srgb, var(--leaf), var(--line) 64%);
    border-radius: 11px;
    background: color-mix(in srgb, var(--paper-raised), var(--leaf) 5%);
    color: var(--ink-soft);
    font-family: var(--sans);
    font-size: 13px;
    scrollbar-width: thin;
}

.model-route-strip span {
    flex: 0 0 auto;
    padding: 7px 10px;
    border: 1px solid var(--line);
    border-radius: 999px;
    background: var(--paper-raised);
    color: var(--ink);
    font-weight: 720;
    white-space: nowrap;
}

.model-route-strip b {
    flex: 0 0 auto;
    color: var(--kumquat-deep);
    font-size: 17px;
}

.d2l-license-card {
    position: relative;
    overflow: hidden;
    padding: 28px 30px 25px;
    border: 1px solid color-mix(in srgb, var(--sky), var(--line) 48%);
    background:
        radial-gradient(circle at 92% 18%, color-mix(in srgb, var(--kumquat), transparent 74%) 0 54px, transparent 55px),
        linear-gradient(135deg, color-mix(in srgb, var(--paper-raised), var(--sky) 9%), var(--paper-raised) 58%);
    box-shadow: inset 5px 0 0 color-mix(in srgb, var(--sky), var(--kumquat) 24%);
}

.d2l-license-card::after {
    position: absolute;
    right: -24px;
    bottom: -34px;
    width: 120px;
    height: 120px;
    border: 1px solid color-mix(in srgb, var(--sky), transparent 72%);
    border-radius: 50%;
    content: "";
}

.d2l-license-card .d2l-mark {
    display: inline-flex;
    margin-bottom: 12px;
    padding: 5px 9px;
    border: 1px solid color-mix(in srgb, var(--sky), var(--line) 45%);
    border-radius: 999px;
    color: var(--sky);
    font-family: var(--sans);
    font-size: 9px;
    font-weight: 850;
    letter-spacing: 0.14em;
    text-transform: uppercase;
}

.d2l-license-card h2 {
    position: relative;
    z-index: 1;
    margin: 0 0 10px;
    color: var(--ink);
    font-size: clamp(24px, 3.1vw, 38px);
    line-height: 1.08;
}

.d2l-license-card p:last-child {
    position: relative;
    z-index: 1;
    max-width: 780px;
    margin-bottom: 0;
}

.formula-card {
    position: relative;
    overflow-x: auto;
    padding: 23px 26px 20px;
    border: 1px solid color-mix(in srgb, var(--sky), var(--line) 62%);
    background: color-mix(in srgb, var(--paper-raised), var(--sky) 4%);
}

.formula-card::before {
    display: block;
    margin-bottom: 12px;
    color: var(--sky);
    content: "公式观察站";
    font-family: var(--sans);
    font-size: 9px;
    font-weight: 800;
    letter-spacing: 0.15em;
}

.formula-card .equation {
    min-width: max-content;
    margin: 5px 0;
    text-align: center;
}

.formula-card p:last-child {
    margin-bottom: 0;
    color: var(--ink-soft);
    font-family: var(--sans);
    font-size: 12px;
}

.callout {
    position: relative;
    padding: 19px 21px 18px 55px;
    border: 1px solid var(--line);
    background: var(--paper-raised);
}

.callout::before {
    position: absolute;
    top: 17px;
    left: 18px;
    display: grid;
    width: 25px;
    height: 25px;
    place-items: center;
    border-radius: 50%;
    background: var(--ink);
    color: var(--paper);
    content: "i";
    font-family: Georgia, serif;
    font-size: 14px;
    font-style: italic;
    font-weight: 800;
}

.callout.warning {
    border-color: color-mix(in srgb, var(--kumquat), var(--line) 55%);
    background: color-mix(in srgb, var(--paper-raised), var(--kumquat) 5%);
}

.callout.warning::before {
    background: var(--kumquat-deep);
    content: "!";
    font-style: normal;
}

.callout.misconception {
    border-color: color-mix(in srgb, var(--danger), var(--line) 70%);
}

.callout.misconception::before {
    background: var(--danger);
    content: "×";
    font-style: normal;
}

.callout-title {
    display: block;
    margin-bottom: 4px;
    font-family: var(--sans);
    font-size: 12px;
    font-weight: 800;
    letter-spacing: 0.04em;
}

.callout p:last-child,
.callout ul:last-child {
    margin-bottom: 0;
}

.worked-example {
    padding: 21px 24px;
    border: 1px dashed color-mix(in srgb, var(--leaf), var(--line) 45%);
    background: color-mix(in srgb, var(--paper-raised), var(--leaf) 4%);
}

.worked-example h3,
.project-card h3,
.knowledge-check h3,
.lab-card h3 {
    margin: 0 0 9px;
}

.example-label,
.project-label,
.quiz-label,
.lab-label {
    display: block;
    margin-bottom: 6px;
    color: var(--leaf);
    font-family: var(--sans);
    font-size: 9px;
    font-weight: 800;
    letter-spacing: 0.15em;
}

.project-card {
    padding: 24px 25px;
    border: 1px solid color-mix(in srgb, var(--kumquat), var(--line) 45%);
    background:
        linear-gradient(105deg, rgba(237, 124, 37, 0.1), transparent 38%),
        var(--paper-raised);
    box-shadow: var(--shadow-small);
}

.project-label {
    color: var(--kumquat-deep);
}

.project-card h3::before {
    margin-right: 8px;
    content: "◎";
    color: var(--kumquat);
}

.visual-figure {
    counter-increment: figure;
    margin: 31px 0;
    padding: 20px;
    border: 1px solid var(--line);
    border-radius: 12px;
    background: var(--paper-raised);
    box-shadow: var(--shadow-small);
}

.visual-figure img {
    width: 100%;
    max-height: 560px;
    object-fit: contain;
}

.visual-figure figcaption {
    margin-top: 14px;
    padding-top: 12px;
    border-top: 1px solid var(--line);
    color: var(--ink-soft);
    font-family: var(--sans);
    font-size: 11px;
    line-height: 1.65;
}

.visual-figure figcaption::before {
    content: "图 " counter(figure) "　";
    color: var(--kumquat-deep);
    font-weight: 800;
}

.table-wrap {
    margin: 25px 0;
    overflow-x: auto;
    border: 1px solid var(--line);
    border-radius: 10px;
    background: var(--paper-raised);
}

table {
    width: 100%;
    min-width: 580px;
    border-collapse: collapse;
    font-size: 12px;
}

caption {
    padding: 10px 14px;
    border-bottom: 1px solid var(--line);
    color: var(--ink-soft);
    caption-side: top;
    font-size: 10px;
    text-align: left;
}

th,
td {
    padding: 11px 14px;
    border-bottom: 1px solid var(--line);
    text-align: left;
    vertical-align: top;
}

th {
    background: color-mix(in srgb, var(--paper-deep), transparent 32%);
    color: var(--ink);
    font-weight: 800;
}

tbody tr:last-child td {
    border-bottom: 0;
}

tbody tr:hover {
    background: color-mix(in srgb, var(--kumquat), transparent 95%);
}

.shape-flow {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 8px;
    margin: 20px 0;
    padding: 17px;
    border-radius: 9px;
    background: var(--forest-950);
    color: #edf4eb;
    font-family: Consolas, "Cascadia Mono", monospace;
    font-size: 11px;
}

.shape-flow .tensor {
    padding: 7px 10px;
    border: 1px solid rgba(255, 255, 255, 0.15);
    border-radius: 5px;
    background: rgba(255, 255, 255, 0.06);
}

.shape-flow .arrow {
    color: #f5a357;
}

.knowledge-check {
    padding: 24px 25px;
    border: 1px solid color-mix(in srgb, var(--sky), var(--line) 58%);
    background: color-mix(in srgb, var(--paper-raised), var(--sky) 3%);
}

.quiz-label {
    color: var(--sky);
}

.answer-toggle {
    margin-top: 8px;
    padding: 7px 11px;
    border: 1px solid var(--line);
    border-radius: 6px;
    background: var(--paper-raised);
    color: var(--sky);
    cursor: pointer;
    font-size: 11px;
    font-weight: 800;
}

.answer {
    margin-top: 13px;
    padding: 13px 15px;
    border-left: 3px solid var(--sky);
    background: color-mix(in srgb, var(--paper), var(--sky) 4%);
    color: var(--ink-soft);
    font-size: 13px;
}

.answer[hidden] {
    display: none;
}

.lab-card {
    padding: 24px 25px;
    border: 1px solid var(--forest-700);
    background: var(--forest-950);
    color: #e9f1e7;
}

.lab-label {
    color: #f6a75c;
}

.lab-card h3,
.lab-card strong {
    color: white;
}

.lab-card code,
.chapter-body code {
    padding: 2px 5px;
    border-radius: 4px;
    background: color-mix(in srgb, var(--paper-deep), transparent 12%);
    font-family: Consolas, "Cascadia Mono", monospace;
    font-size: 0.84em;
}

.lab-card code {
    background: rgba(255, 255, 255, 0.08);
}

pre {
    margin: 14px 0;
    padding: 16px;
    overflow: auto;
    border-radius: 7px;
    background: #081b12;
    color: #daf0df;
    line-height: 1.62;
}

pre code {
    padding: 0 !important;
    background: transparent !important;
}

.source-panel {
    margin-top: 58px;
    padding: 24px 26px;
    border-top: 3px solid var(--ink);
    background: color-mix(in srgb, var(--paper-raised), var(--ink) 2%);
}

.source-panel h2 {
    margin: 0 0 5px;
    font-family: var(--serif);
    font-size: 18px;
}

.source-panel > p {
    margin: 0 0 13px;
    color: var(--ink-soft);
    font-size: 11px;
}

.source-list {
    margin: 0;
    padding-left: 19px;
}

.source-list li {
    font-family: var(--sans);
    font-size: 12px;
}

.source-list small {
    display: block;
    color: var(--ink-soft);
}

.chapter-controls {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: 11px;
    margin-top: 54px;
    padding-top: 24px;
    border-top: 1px solid var(--line);
}

.chapter-nav-button,
.complete-button {
    min-height: 62px;
    border: 1px solid var(--line);
    border-radius: 9px;
    background: var(--paper-raised);
    cursor: pointer;
}

.chapter-nav-button {
    display: flex;
    flex-direction: column;
    justify-content: center;
    padding: 9px 13px;
    text-align: left;
}

.chapter-nav-button.next {
    text-align: right;
}

.chapter-nav-button small {
    color: var(--ink-soft);
    font-size: 9px;
}

.chapter-nav-button strong {
    overflow: hidden;
    max-width: 210px;
    font-size: 11px;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.chapter-nav-button:not(:disabled):hover {
    border-color: var(--kumquat);
}

.chapter-nav-button:disabled {
    opacity: 0.35;
    cursor: default;
}

.complete-button {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 0 15px;
    font-size: 10px;
    font-weight: 800;
}

.complete-dot {
    display: grid;
    width: 21px;
    height: 21px;
    place-items: center;
    border: 1px solid var(--line);
    border-radius: 50%;
    color: transparent;
}

.complete-button.completed {
    border-color: var(--leaf);
    background: color-mix(in srgb, var(--paper-raised), var(--leaf) 8%);
}

.complete-button.completed .complete-dot {
    border-color: var(--leaf);
    background: var(--leaf);
    color: white;
}

.study-rail {
    position: sticky;
    top: 92px;
    align-self: start;
}

.rail-card {
    margin-bottom: 13px;
    padding: 17px;
    border: 1px solid var(--line);
    border-radius: 9px;
    background: color-mix(in srgb, var(--paper-raised), transparent 16%);
}

.rail-eyebrow,
.dialog-eyebrow {
    margin: 0;
    color: var(--ink-soft);
    font-size: 9px;
    font-weight: 800;
    letter-spacing: 0.14em;
}

.chapter-outline {
    margin-top: 11px;
}

.outline-link {
    display: block;
    margin: 2px 0;
    padding: 5px 8px;
    border-left: 1px solid var(--line);
    color: var(--ink-soft);
    font-size: 10px;
    line-height: 1.45;
    text-decoration: none;
}

.outline-link.level-3 {
    padding-left: 17px;
    font-size: 9px;
}

.outline-link:hover,
.outline-link.active {
    border-left-color: var(--kumquat);
    color: var(--ink);
}

.rail-title-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.rail-title-row span {
    color: var(--leaf);
    font-size: 8px;
}

.notes-card textarea {
    width: 100%;
    margin-top: 10px;
    padding: 10px;
    resize: vertical;
    border: 1px dashed var(--line);
    border-radius: 6px;
    outline: 0;
    background:
        repeating-linear-gradient(transparent, transparent 26px, color-mix(in srgb, var(--line), transparent 35%) 27px),
        var(--paper-raised);
    color: var(--ink);
    font-family: var(--serif);
    font-size: 11px;
    line-height: 27px;
}

.notes-card textarea:focus {
    border-color: var(--kumquat);
}

.shortcut-card p:last-child {
    margin: 9px 0 0;
    color: var(--ink-soft);
    font-size: 9px;
}

.search-dialog {
    width: min(680px, calc(100vw - 32px));
    max-height: min(730px, calc(100vh - 36px));
    padding: 0;
    overflow: hidden;
    border: 1px solid var(--line);
    border-radius: 14px;
    background: var(--paper-raised);
    color: var(--ink);
    box-shadow: 0 30px 100px rgba(10, 25, 17, 0.28);
}

.search-dialog::backdrop {
    background: rgba(6, 18, 12, 0.61);
    backdrop-filter: blur(3px);
}

.search-dialog-head {
    display: flex;
    align-items: start;
    justify-content: space-between;
    padding: 22px 24px 13px;
}

.search-dialog h2,
.term-drawer h2 {
    margin: 2px 0 0;
    font-family: var(--serif);
    font-size: 22px;
}

.dialog-search {
    margin: 0 24px;
    padding: 10px 13px;
    background: var(--paper);
    color: var(--ink-soft);
}

.dialog-search input {
    min-width: 0;
    flex: 1;
    border: 0;
    outline: 0;
    background: transparent;
    color: var(--ink);
}

.search-results {
    max-height: 510px;
    min-height: 160px;
    overflow-y: auto;
    padding: 13px 24px 26px;
}

.search-empty {
    padding: 40px 15px;
    color: var(--ink-soft);
    text-align: center;
}

.search-result {
    display: block;
    width: 100%;
    margin: 5px 0;
    padding: 13px 15px;
    border: 1px solid transparent;
    border-radius: 8px;
    background: transparent;
    color: inherit;
    cursor: pointer;
    text-align: left;
}

.search-result:hover {
    border-color: var(--line);
    background: var(--paper);
}

.search-result small,
.search-result strong,
.search-result span {
    display: block;
}

.search-result small {
    color: var(--kumquat-deep);
    font-size: 9px;
    font-weight: 800;
    letter-spacing: 0.08em;
}

.search-result strong {
    margin: 2px 0;
    font-family: var(--serif);
    font-size: 14px;
}

.search-result span {
    overflow: hidden;
    color: var(--ink-soft);
    font-size: 10px;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.term-drawer {
    position: fixed;
    z-index: 85;
    top: 0;
    right: 0;
    display: flex;
    width: min(425px, 93vw);
    height: 100vh;
    flex-direction: column;
    border-left: 1px solid var(--line);
    background: var(--paper-raised);
    color: var(--ink);
    box-shadow: -20px 0 60px rgba(10, 25, 17, 0.2);
    transform: translateX(102%);
    transition: transform 0.28s cubic-bezier(0.22, 1, 0.36, 1);
}

.term-drawer.open {
    transform: translateX(0);
}

.drawer-head {
    display: flex;
    align-items: start;
    justify-content: space-between;
    padding: 26px 25px 19px;
    border-bottom: 1px solid var(--line);
}

.term-content {
    flex: 1;
    overflow-y: auto;
    padding: 25px;
}

.term-content .term-en {
    display: block;
    margin-bottom: 13px;
    color: var(--kumquat-deep);
    font-size: 10px;
    font-weight: 800;
    letter-spacing: 0.1em;
    text-transform: uppercase;
}

.term-content p {
    font-family: var(--serif);
}

.term-content .plain-explanation {
    padding: 15px 17px;
    border-left: 3px solid var(--kumquat);
    background: var(--paper);
}

.drawer-footer {
    padding: 15px 25px 23px;
    border-top: 1px solid var(--line);
}

.secondary-button {
    width: 100%;
    padding: 9px;
    color: var(--ink-soft);
}

.drawer-scrim {
    position: fixed;
    z-index: 80;
    inset: 0;
    background: rgba(7, 19, 12, 0.48);
}

.resume-toast {
    position: fixed;
    z-index: 75;
    right: 24px;
    bottom: 23px;
    display: grid;
    grid-template-columns: 39px minmax(0, 1fr) auto;
    width: min(440px, calc(100vw - 32px));
    align-items: center;
    gap: 12px;
    padding: 13px 14px;
    border: 1px solid var(--line);
    border-radius: 10px;
    background: var(--paper-raised);
    box-shadow: var(--shadow);
}

.resume-toast[hidden] {
    display: none;
}

.resume-seal {
    display: grid;
    width: 38px;
    height: 38px;
    place-items: center;
    border-radius: 50%;
    background: var(--forest-800);
    color: white;
    font-family: var(--serif);
    font-weight: 800;
}

.resume-toast strong,
.resume-toast p {
    display: block;
    margin: 0;
}

.resume-toast strong {
    font-size: 11px;
}

.resume-toast p {
    color: var(--ink-soft);
    font-size: 9px;
}

.resume-toast button {
    border: 0;
    background: transparent;
    color: var(--sky);
    cursor: pointer;
    font-size: 10px;
}

@media (max-width: 1180px) {
    .reader-layout {
        grid-template-columns: minmax(0, var(--reading-width));
    }

    .study-rail {
        display: none;
    }
}

@media (max-width: 860px) {
    :root {
        --sidebar-width: 286px;
    }

    .sidebar {
        transform: translateX(-103%);
        transition: transform 0.28s cubic-bezier(0.22, 1, 0.36, 1);
    }

    .sidebar.open {
        transform: translateX(0);
    }

    .sidebar-close,
    .menu-button {
        display: inline-grid;
    }

    .page-column {
        margin-left: 0;
    }

    .reading-line {
        left: 0;
    }

    .reader-layout {
        padding: 42px 19px 70px;
    }

    .chapter-hero {
        padding: 27px 24px;
    }

    .learning-objectives ul {
        grid-template-columns: 1fr;
    }

    .sidebar.open::before {
        position: fixed;
        z-index: -1;
        inset: 0 -100vw 0 0;
        background: rgba(6, 17, 11, 0.56);
        content: "";
    }
}

@media (max-width: 590px) {
    body {
        font-size: 15px;
    }

    .topbar {
        height: 58px;
        padding: 0 12px;
    }

    .breadcrumb span,
    .return-button {
        display: none;
    }

    .topbar-actions {
        gap: 5px;
    }

    .reading-line {
        top: 57px;
    }

    .reader-layout {
        padding: 28px 13px 60px;
    }

    .chapter-hero {
        margin-bottom: 27px;
        padding: 23px 20px;
        border-radius: 12px 12px 12px 3px;
    }

    .chapter-hero h1 {
        font-size: 29px;
    }

    .chapter-summary {
        font-size: 15px;
    }

    .learning-objectives {
        padding: 19px 20px;
    }

    .chapter-body > h2 {
        margin-top: 46px;
        font-size: 22px;
    }

    .chapter-body p,
    .chapter-body li {
        font-size: 15px;
    }

    .formula-card,
    .project-card,
    .knowledge-check,
    .lab-card {
        padding: 19px;
    }

    .official-doc-card {
        padding: 22px 19px;
    }

    .official-doc-card::after {
        right: 14px;
        top: 15px;
        width: 52px;
        height: 52px;
        font-size: 25px;
        line-height: 50px;
    }

    .official-doc-card h2 {
        margin-right: 58px;
    }

    .callout {
        padding-left: 50px;
    }

    .visual-figure {
        padding: 12px;
    }

    .chapter-controls {
        grid-template-columns: 1fr 1fr;
    }

    .complete-button {
        grid-column: 1 / -1;
        grid-row: 1;
        justify-content: center;
    }

    .chapter-nav-button strong {
        max-width: 135px;
    }

    .resume-toast {
        right: 16px;
        bottom: 15px;
        grid-template-columns: 35px 1fr;
    }

    .resume-toast button {
        display: none;
    }
}

@media print {
    :root {
        --paper: #fff;
        --paper-raised: #fff;
        --ink: #111;
        --ink-soft: #444;
    }

    .sidebar,
    .topbar,
    .reading-line,
    .study-rail,
    .chapter-controls,
    .ambient,
    .resume-toast {
        display: none !important;
    }

    .page-column {
        margin: 0;
    }

    .reader-layout {
        display: block;
        padding: 0;
    }

    .chapter-hero,
    .visual-figure,
    .project-card {
        box-shadow: none;
    }

    .chapter-body > h2,
    .formula-card,
    .visual-figure,
    .table-wrap {
        break-inside: avoid;
    }
}