:root {
    color-scheme: light;
    --color-page: #f6f6f3;
    --color-paper: #ffffff;
    --color-ink: #111111;
    --color-muted: #666666;
    --color-subtle: #e7e7e2;
    --color-line: #d4d4cd;
    --color-accent: #0b57d0;
    --color-accent-soft: #e8f0fe;
    --color-success: #177245;
    --color-warning: #9a5b00;
    --space-1: 0.25rem;
    --space-2: 0.5rem;
    --space-3: 0.75rem;
    --space-4: 1rem;
    --space-5: 1.5rem;
    --space-6: 2rem;
    --space-7: 3rem;
    --radius: 8px;
    --shadow: 0 24px 70px rgba(0, 0, 0, 0.08);
    --fast: 160ms ease;
    --slow: 420ms cubic-bezier(0.22, 1, 0.36, 1);
    --desktop-nav-width: 300px;
    --desktop-content-width: 800px;
    --desktop-layout-gap: 32px;
}

* {
    box-sizing: border-box;
}

html,
body {
    overflow-x: hidden;
}

html {
    background: var(--color-page);
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    width: min(100% - 24px, 1040px);
    margin: 12px auto 48px;
    padding: 0;
    background: var(--color-paper);
    color: var(--color-ink);
    font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif !important;
    font-size: 1rem;
    line-height: 1.65;
    box-shadow: var(--shadow);
}

#breadcrumb,
.page-content,
#footer-placeholder {
    padding-right: clamp(16px, 2.4vw, 32px);
    padding-left: clamp(16px, 2.4vw, 32px);
}

.page-content {
    display: flow-root;
    min-width: 0;
    overflow-wrap: anywhere;
}

.page-content > :first-child {
    margin-top: 0;
}

.page-content > :last-child {
    margin-bottom: 0;
}

.page-content > ul,
.page-content > ol {
    max-width: none;
}

::selection {
    background: var(--color-ink);
    color: var(--color-paper);
}

h1,
h2,
h3,
h4,
h5,
h6 {
    max-width: 18ch;
    margin: var(--space-6) 0 var(--space-3);
    color: var(--color-ink);
    font-family: inherit !important;
    font-weight: 650;
    line-height: 1.08;
    letter-spacing: 0;
}

h1 {
    font-size: clamp(1.9rem, 5vw, 3.4rem);
    font-weight: 720;
}

h2 {
    font-size: clamp(1.4rem, 3vw, 2.1rem);
}

h3 {
    font-size: clamp(1.15rem, 2vw, 1.45rem);
}

h4 {
    font-size: 1.1rem;
}

p {
    margin: var(--space-4) 0;
    max-width: none;
    overflow-wrap: anywhere;
}

a {
    color: var(--color-accent);
    text-decoration-thickness: 1px;
    text-underline-offset: 0.18em;
    transition: color var(--fast), background-color var(--fast), transform var(--fast);
}

a:hover {
    color: var(--color-ink);
    background: var(--color-accent-soft);
}

a:focus-visible,
button:focus-visible,
summary:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible {
    outline: 2px solid var(--color-accent);
    outline-offset: 3px;
}

ul,
ol {
    padding-left: 1.3rem;
}

li {
    margin: 0.45rem 0;
}

button,
input,
select,
textarea {
    font: inherit;
}

button,
input[type="submit"] {
    min-height: 44px;
    border: 1px solid var(--color-ink);
    border-radius: var(--radius);
    padding: 0.7rem 1rem;
    background: var(--color-ink);
    color: var(--color-paper);
    cursor: pointer;
    transition: transform var(--fast), background-color var(--fast), color var(--fast), border-color var(--fast);
}

button:hover,
input[type="submit"]:hover {
    background: var(--color-accent);
    border-color: var(--color-accent);
}

button:disabled {
    cursor: not-allowed;
    opacity: 0.45;
}

input,
select,
textarea {
    width: min(100%, 420px);
    min-height: 44px;
    border: 1px solid var(--color-line);
    border-radius: var(--radius);
    padding: 0.7rem 0.8rem;
    background: var(--color-paper);
    color: var(--color-ink);
}

img,
iframe {
    display: block;
    width: auto;
    max-width: 100%;
    height: auto;
    margin: var(--space-5) auto;
    border: 1px solid var(--color-line);
    border-radius: var(--radius);
}

iframe {
    width: 100%;
    height: clamp(260px, 58vw, 620px);
}

figure {
    margin: var(--space-6) 0;
    text-align: center;
}

figcaption {
    margin-top: var(--space-2);
    color: var(--color-muted);
    font-size: 0.9rem;
}

samp {
    display: none;
}

.katex {
    font-family: inherit !important;
    font-size: 1em !important;
}

.katex-display {
    max-width: 100%;
    overflow-x: auto;
    overflow-y: hidden;
    padding-bottom: 0.15rem;
}

pre,
code {
    max-width: 100%;
    white-space: pre-wrap;
    overflow-wrap: anywhere;
}

.site-header {
    position: sticky;
    top: 0;
    z-index: 20;
    margin: 0 0 var(--space-5);
    padding: 0;
    background: rgba(255, 255, 255, 0.9);
    border-bottom: 1px solid var(--color-line);
    backdrop-filter: blur(18px);
}

.site-bar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-4);
    min-height: 56px;
    padding: 8px clamp(16px, 2.4vw, 32px);
    border-bottom: 1px solid var(--color-line);
}

.brand {
    display: inline-flex;
    align-items: center;
    flex: 1 1 auto;
    gap: var(--space-3);
    min-width: 0;
    color: var(--color-ink);
    text-decoration: none;
}

.brand:hover {
    background: transparent;
}

.brand-mark {
    display: inline-grid;
    width: 34px;
    height: 34px;
    place-items: center;
    border: 1px solid var(--color-ink);
    border-radius: 50%;
    font-weight: 720;
}

.brand-text {
    min-width: 0;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    font-size: 1.05rem;
    font-weight: 680;
    letter-spacing: 0;
}

.auth-controls {
    display: flex;
    align-items: center;
    flex: 0 0 auto;
    gap: var(--space-2);
}

.auth-button,
.progress-link {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    min-height: 36px;
    border: 1px solid var(--color-line);
    border-radius: var(--radius);
    padding: 0;
    background: var(--color-paper);
    color: var(--color-ink);
    font-size: 1rem;
    font-weight: 650;
    line-height: 1;
    text-decoration: none;
}

.icon-button svg {
    width: 18px;
    height: 18px;
    fill: none;
    stroke: currentColor;
    stroke-width: 1.8;
    stroke-linecap: round;
    stroke-linejoin: round;
}

.auth-button:hover,
.progress-link:hover {
    border-color: var(--color-accent);
    background: var(--color-accent-soft);
    color: var(--color-accent);
}

.nav-toggle {
    display: inline-flex;
    align-items: center;
    flex: 0 0 auto;
    gap: var(--space-2);
    min-width: 100px;
    justify-content: center;
    background: var(--color-paper);
    color: var(--color-ink);
}

.nav-toggle:hover,
.nav-toggle.is-active {
    background: var(--color-ink);
    color: var(--color-paper);
}

.nav-toggle-lines,
.nav-toggle-lines::before,
.nav-toggle-lines::after {
    display: block;
    width: 18px;
    height: 1px;
    background: currentColor;
    transition: transform var(--fast), opacity var(--fast);
}

.nav-toggle-lines {
    position: relative;
}

.nav-toggle-lines::before,
.nav-toggle-lines::after {
    content: "";
    position: absolute;
    left: 0;
}

.nav-toggle-lines::before {
    top: -6px;
}

.nav-toggle-lines::after {
    top: 6px;
}

.nav-toggle.is-active .nav-toggle-lines {
    transform: rotate(45deg);
}

.nav-toggle.is-active .nav-toggle-lines::before {
    opacity: 0;
}

.nav-toggle.is-active .nav-toggle-lines::after {
    transform: translateY(-6px) rotate(-90deg);
}

.nav-panel {
    max-height: 0;
    overflow: hidden;
    opacity: 0;
    transform: translateY(-6px);
    visibility: hidden;
    transition: max-height var(--slow), opacity var(--fast), transform var(--fast), visibility var(--fast);
}

.nav-panel.is-open {
    max-height: min(78vh, 760px);
    overflow-y: auto;
    opacity: 1;
    transform: translateY(0);
    visibility: visible;
}

.nav-section a,
.nav-direct,
.nav-section summary,
.nav-topic summary {
    min-height: 44px;
    border-radius: var(--radius);
    text-decoration: none;
}

.nav-sections {
    display: flex;
    width: min(calc(100% - 32px), 340px);
    flex-direction: column;
    gap: 0.35rem;
    margin-top: var(--space-4);
    margin-right: auto;
    margin-left: clamp(16px, 2.4vw, 32px);
    position: relative;
}

.nav-section {
    position: relative;
    border: 0;
    border-radius: calc(var(--radius) + 2px);
    background: var(--color-paper);
}

.nav-direct {
    display: flex;
    align-items: center;
    border: 0;
    padding: 0.72rem 0.9rem;
    background: transparent;
    color: var(--color-ink);
    font-weight: 640;
}

.nav-direct:hover,
.nav-direct.active {
    background: var(--color-accent-soft);
    color: var(--color-accent);
}

.nav-section summary,
.nav-topic summary {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-2);
    padding: 0.72rem 0.9rem;
    color: var(--color-ink);
    cursor: pointer;
    font-weight: 640;
    list-style: none;
}

.nav-topic summary {
    min-height: 40px;
    padding: 0.55rem 0.65rem;
    color: var(--color-muted);
    font-size: 0.95rem;
    font-weight: 600;
}

.nav-section summary::-webkit-details-marker,
.nav-topic summary::-webkit-details-marker {
    display: none;
}

.nav-section summary::after,
.nav-topic summary::after {
    content: "+";
    font-size: 1.2rem;
    line-height: 1;
}

.nav-section[open] > summary::after,
.nav-topic[open] > summary::after {
    content: "-";
    color: var(--color-accent);
}

.nav-section ul,
.nav-topic ul {
    position: static;
    width: auto;
    max-height: none;
    overflow: visible;
    margin: 0;
    list-style: none;
}

.nav-topics {
    padding: 0 0 var(--space-2);
}

.nav-section li {
    margin: 0;
}

.nav-topic {
    border-top: 1px solid var(--color-line);
}

.nav-pages {
    padding: 0 0 var(--space-2) var(--space-3);
}

.nav-section a {
    display: flex;
    align-items: center;
    margin: 0;
    min-height: 36px;
    padding: 0.45rem 0.65rem;
    color: var(--color-muted);
    font-size: 0.95rem;
}

.nav-section a:hover,
.nav-section a.active {
    background: var(--color-accent-soft);
    color: var(--color-accent);
}

.home-sections {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(min(100%, 240px), 1fr));
    gap: var(--space-5) var(--space-6);
    margin: var(--space-5) 0;
}

.home-sections section {
    border-top: 1px solid var(--color-line);
}

.home-sections h2 {
    max-width: none;
    margin: var(--space-3) 0 var(--space-2);
    font-size: 1rem;
    line-height: 1.25;
}

.home-sections ul {
    display: grid;
    gap: 0.2rem;
    margin: 0;
    padding: 0;
    list-style: none;
}

.home-sections li {
    margin: 0;
}

.home-sections a {
    display: block;
    padding: 0.32rem 0;
    color: var(--color-ink);
    text-decoration: none;
}

.home-sections a:hover {
    color: var(--color-accent);
    background: transparent;
}

.auto-understanding-check {
    margin-top: var(--space-7);
}

.understanding-form {
    display: grid;
    gap: var(--space-4);
}

.understanding-question {
    display: grid;
    gap: var(--space-2);
    margin: 0;
    border: 1px solid var(--color-line);
    border-radius: var(--radius);
    padding: var(--space-4);
}

.understanding-question legend {
    padding: 0 var(--space-2);
    font-weight: 650;
}

.understanding-question label {
    display: flex;
    align-items: flex-start;
    gap: var(--space-2);
    margin: 0;
}

.understanding-question input {
    width: auto;
    min-height: auto;
    margin-top: 0.35rem;
}

.understanding-question .understanding-numeric {
    align-items: center;
}

.understanding-question .understanding-numeric input {
    width: min(100%, 180px);
    min-height: 40px;
    margin-top: 0;
}

.understanding-feedback {
    margin: var(--space-2) 0 0;
    color: var(--color-muted);
    font-size: 0.95rem;
}

.understanding-question.is-correct {
    border-color: var(--color-success);
    background: rgba(23, 114, 69, 0.06);
}

.understanding-question.is-incorrect {
    border-color: var(--color-warning);
    background: rgba(154, 91, 0, 0.07);
}

.understanding-result {
    margin: 0;
    font-weight: 650;
}

.progress-summary,
.progress-list {
    margin: var(--space-5) 0;
}

.progress-stats {
    display: grid;
    grid-template-columns: auto 1fr auto 1fr;
    gap: var(--space-2) var(--space-3);
    align-items: baseline;
    width: fit-content;
    border-top: 1px solid var(--color-line);
    border-bottom: 1px solid var(--color-line);
    padding: var(--space-3) 0;
}

.progress-stats strong {
    font-size: 1.8rem;
    line-height: 1;
}

.progress-stats span,
.progress-list small {
    color: var(--color-muted);
}

.progress-list ul {
    display: grid;
    gap: var(--space-2);
    margin: 0;
    padding: 0;
    list-style: none;
}

.progress-list li {
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto auto;
    gap: var(--space-3);
    align-items: center;
    margin: 0;
    border-top: 1px solid var(--color-line);
    padding: var(--space-3) 0;
}

.progress-list span {
    font-weight: 650;
}

.breadcrumb {
    display: flex;
    flex-wrap: wrap;
    gap: 0.35rem;
    margin: 0 0 var(--space-5);
    padding: 0;
    color: var(--color-muted);
    font-size: 0.875rem;
    list-style: none;
}

.breadcrumb li {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    margin: 0;
}

.breadcrumb li + li::before {
    content: "/";
    color: var(--color-line);
}

.breadcrumb a {
    color: var(--color-muted);
    text-decoration: none;
}

.breadcrumb a:hover {
    color: var(--color-accent);
}

.stylish-list ol {
    display: grid;
    gap: var(--space-2);
    margin: var(--space-5) 0;
    padding-left: 0;
    list-style: none;
    counter-reset: list-item;
}

.stylish-list li {
    counter-increment: list-item;
    position: relative;
    margin: 0;
    border-top: 1px solid var(--color-line);
}

.stylish-list li::before {
    content: counter(list-item, decimal-leading-zero);
    position: absolute;
    top: 0.8rem;
    left: 0;
    color: var(--color-muted);
    font-size: 0.78rem;
    font-weight: 650;
}

.stylish-list a {
    display: block;
    min-height: 48px;
    margin-left: 2.5rem;
    padding: 0.72rem 0.5rem;
    color: var(--color-ink);
    text-decoration: none;
}

.stylish-list a:hover {
    color: var(--color-accent);
    background: var(--color-accent-soft);
    transform: translateX(4px);
}

.learning-outcome {
    margin: var(--space-6) 0;
    padding: var(--space-5);
    border: 1px solid var(--color-line);
    border-radius: var(--radius);
    background: var(--color-page);
}

.learning-outcome ol li {
    margin-top: 0.7rem;
}

.container,
.callout,
.quiz-container {
    width: 100%;
    margin: var(--space-5) 0;
    border: 1px solid var(--color-line);
    border-radius: var(--radius);
    background: var(--color-paper);
}

.container {
    display: flex;
    flex-direction: column;
    gap: var(--space-3);
    padding: var(--space-5);
}

.container > * {
    width: 100%;
}

.callout {
    display: flex;
    gap: var(--space-4);
    align-items: flex-start;
    padding: var(--space-5);
    border-left: 4px solid var(--color-accent);
    color: var(--color-ink);
}

.callout.warning {
    border-left-color: var(--color-warning);
    background: #fff8e6;
}

.callout.note {
    border-left-color: var(--color-muted);
    background: var(--color-page);
}

.callout .emoji,
.callout .icon {
    display: inline-grid;
    width: 38px;
    height: 38px;
    place-items: center;
    flex: 0 0 auto;
    border: 1px solid var(--color-line);
    border-radius: 50%;
    background: var(--color-page);
}

.callout .callout-text {
    flex: 1;
}

.callout strong {
    color: var(--color-ink);
    font-weight: 680;
}

.table-wrapper {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

table {
    width: 100%;
    min-width: 520px;
    border-collapse: collapse;
    margin: var(--space-5) 0;
    font-size: 0.95rem;
}

th,
td {
    padding: 0.85rem;
    border-bottom: 1px solid var(--color-line);
    text-align: left;
    vertical-align: top;
}

th {
    background: var(--color-ink);
    color: var(--color-paper);
    font-weight: 650;
}

tr:nth-child(even) {
    background: var(--color-page);
}

.accordion {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    margin: var(--space-3) 0 0;
    background: var(--color-paper);
    color: var(--color-ink);
}

.accordion.active {
    background: var(--color-ink);
    color: var(--color-paper);
}

.score {
    clear: both;
    display: block;
    margin-top: var(--space-4);
    color: var(--color-muted);
    font-size: 0.9rem;
    font-style: italic;
}

#feedback {
    color: var(--color-accent);
    font-style: italic;
}

.quiz-container {
    overflow: hidden;
}

.quiz-container h3 {
    max-width: none;
    margin: 0;
    padding: var(--space-5);
    border-bottom: 1px solid var(--color-line);
    background: var(--color-page);
    font-size: 1.1rem;
}

.quiz-container .quiz-content,
.quiz-container > :not(h3):not(.quiz-content) {
    margin: 0;
    padding: var(--space-5);
}

.quiz-container .problem-box,
.quiz-container .solution-box,
.quiz-container .choice-option {
    border: 1px solid var(--color-line);
    border-radius: var(--radius);
    background: var(--color-page);
}

.quiz-container .problem-box {
    min-height: 80px;
    margin-bottom: var(--space-4);
    padding: var(--space-5);
}

.quiz-container .button-container,
.quiz-container .choice-container {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-3);
    margin-bottom: var(--space-5);
}

.quiz-container .choice-container {
    flex-direction: column;
}

.quiz-container button {
    min-height: 44px;
}

.quiz-container button.secondary {
    background: var(--color-paper);
    color: var(--color-ink);
}

.quiz-container .choice-option {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    min-height: 48px;
    padding: var(--space-3) var(--space-4);
    cursor: pointer;
    transition: background-color var(--fast), border-color var(--fast), transform var(--fast);
}

.quiz-container .choice-option:hover,
.quiz-container .choice-option.selected {
    border-color: var(--color-accent);
    background: var(--color-accent-soft);
}

.quiz-container .choice-option input[type="radio"] {
    width: auto;
    min-height: auto;
    accent-color: var(--color-accent);
}

.quiz-container .quiz-footer {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    gap: var(--space-3);
    padding-top: var(--space-4);
    border-top: 1px solid var(--color-line);
}

.quiz-container .score-display {
    color: var(--color-muted);
    font-weight: 620;
}

.quiz-container .feedback-display.correct {
    color: var(--color-success);
}

.quiz-container .feedback-display.incorrect {
    color: #b3261e;
}

.quiz-container .progress-container {
    height: 6px;
    margin-top: var(--space-5);
    overflow: hidden;
    border-radius: 999px;
    background: var(--color-line);
}

.quiz-container .progress-bar {
    height: 100%;
    width: 0%;
    border-radius: inherit;
    background: var(--color-accent);
    transition: width var(--slow);
}

.quiz-container .solution-box {
    display: none;
    margin-top: var(--space-4);
    padding: var(--space-4);
    border-left: 4px solid var(--color-success);
}

.quiz-container .quiz-success {
    text-align: center;
}

.quiz-container .quiz-success .emoji {
    display: block;
    margin-bottom: var(--space-3);
    font-size: 2rem;
}

.quiz-container .quiz-success .title {
    margin-bottom: var(--space-2);
    color: var(--color-accent);
    font-size: 1.35rem;
    font-weight: 680;
}

footer,
#footer-placeholder {
    margin-top: var(--space-7);
    color: var(--color-muted);
    font-size: 0.88rem;
}

.site-footer {
    display: grid;
    gap: var(--space-3);
    border-top: 1px solid var(--color-line);
    padding-top: var(--space-4);
}

.footer-links {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-4);
}

.footer-links a,
.footer-license a {
    color: var(--color-accent);
}

.footer-license {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: var(--space-2);
    max-width: none;
    margin: 0;
}

#footer-placeholder img {
    display: inline-block;
    margin: 0 0.35rem 0 0;
    vertical-align: middle;
    border: 0;
}

.footer-license img {
    width: 88px;
    height: 31px;
}

.is-pressing {
    transform: scale(0.98);
}

.reveal-on-scroll {
    opacity: 0;
    transform: translateY(14px);
    transition: opacity var(--slow), transform var(--slow);
}

.reveal-on-scroll.is-visible {
    opacity: 1;
    transform: translateY(0);
}

@media (min-width: 760px) {
    body {
        margin-top: 24px;
    }

    .site-header {
        margin: 0 0 var(--space-6);
    }

    .nav-panel.is-open {
        padding-bottom: var(--space-1);
    }
}

@media (min-width: 980px) {
    body {
        width: min(
            calc(100% - 32px),
            calc(var(--desktop-nav-width) + var(--desktop-layout-gap) + var(--desktop-content-width))
        );
        min-height: calc(100vh - 72px);
    }

    .site-header {
        position: fixed;
        top: 0;
        left: max(
            16px,
            calc(
                (100vw - (var(--desktop-nav-width) + var(--desktop-layout-gap) + var(--desktop-content-width))) / 2
            )
        );
        width: min(
            calc(100% - 32px),
            calc(var(--desktop-nav-width) + var(--desktop-layout-gap) + var(--desktop-content-width))
        );
        height: 52px;
        margin: 0;
        padding: 0;
        overflow: visible;
        border: 1px solid var(--color-line);
        background: var(--color-paper);
        box-shadow: none;
        backdrop-filter: none;
    }

    .site-bar {
        align-items: center;
        min-height: 52px;
        padding: 8px 12px;
    }

    .nav-toggle {
        display: none;
    }

    .nav-panel,
    .nav-panel.is-open {
        position: absolute;
        top: 52px;
        left: 0;
        width: var(--desktop-nav-width);
        max-height: none;
        overflow: visible;
        opacity: 1;
        transform: none;
        visibility: visible;
    }

    .nav-panel {
        max-height: calc(100vh - 100px);
        overflow-y: auto;
        border: 1px solid var(--color-line);
        border-top: 0;
        background: var(--color-paper);
    }

    .nav-sections {
        width: 100%;
        margin-top: var(--space-3);
        margin-left: 0;
        padding: 0 12px 12px;
    }

    #breadcrumb,
    .page-content,
    #footer-placeholder {
        width: var(--desktop-content-width);
        max-width: 100%;
        margin-left: calc(var(--desktop-nav-width) + var(--desktop-layout-gap));
    }

    #breadcrumb {
        padding-top: 80px;
    }
}

@media (max-width: 700px) {
    body {
        width: 100%;
        margin: 0;
        padding: 0;
        box-shadow: none;
    }

    #breadcrumb,
    .page-content,
    #footer-placeholder {
        padding-right: 16px;
        padding-left: 16px;
        max-width: 100%;
        overflow-x: hidden;
    }

    h1,
    h2,
    h3,
    h4,
    h5,
    h6,
    li,
    label,
    legend,
    summary,
    blockquote {
        overflow-wrap: anywhere;
    }

    table {
        min-width: 0;
    }

    iframe {
        width: 100% !important;
        max-width: 100%;
    }

    .site-header {
        margin: 0 0 var(--space-5);
        padding: 0;
    }

    .site-bar {
        gap: var(--space-2);
        min-height: 54px;
        padding: 8px 16px;
    }

    .brand-mark {
        width: 34px;
        height: 34px;
    }

    .nav-toggle {
        min-width: 72px;
        padding-inline: 0.85rem;
    }

    .auth-button,
    .progress-link {
        width: 34px;
        min-height: 36px;
        font-size: 0.95rem;
    }

    .auth-controls {
        gap: 6px;
    }

    .nav-sections {
        width: calc(100% - 32px);
        margin-left: 16px;
    }

    .nav-panel.is-open {
        overflow-y: auto;
    }

    .nav-section ul {
        position: static;
        width: auto;
        max-height: none;
        margin: 0;
        border: 0;
        border-top: 1px solid var(--color-line);
        border-radius: 0 0 var(--radius) var(--radius);
        box-shadow: none;
    }

    .nav-section summary::after {
        content: "+";
    }

    .nav-section[open] summary::after {
        content: "-";
    }

    .learning-outcome,
    .container,
    .callout,
    .quiz-container .quiz-content,
    .quiz-container > :not(h3):not(.quiz-content) {
        padding: var(--space-4);
    }

    .callout {
        flex-direction: column;
    }

    .quiz-container .button-container {
        flex-direction: column;
    }

    .quiz-container button,
    .quiz-container .button-container button {
        width: 100%;
    }
}

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        scroll-behavior: auto !important;
        transition-duration: 0.01ms !important;
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
    }

    .reveal-on-scroll {
        opacity: 1;
        transform: none;
    }
}