/* ===========================================
   YouTube University - Project Styles
   =========================================== */

/* YouTube University runs slightly smaller than the site default (18px) for
   a denser, more reading-oriented feel — closer to the typography scale of
   reference sites like Teaching AI Ethics. All spacing and type in this
   project uses rem, so this single override scales everything uniformly. */
html:has(.yt-video-page),
html:has(.yt-course-page),
html:has(.yt-index-page) {
    font-size: 17px;
}

/* Controls (search, depth, tags) */

.yt-controls {
    margin: var(--spacing-md) 0 var(--spacing-lg);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.yt-control-row {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
    align-items: flex-end;
}

.yt-control-label {
    display: block;
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.25rem;
}

.yt-search-label {
    flex: 1 1 280px;
}

.yt-depth-label,
.yt-sort-label {
    flex: 0 0 auto;
}

.yt-view-toggle {
    flex: 0 0 auto;
    display: flex;
    flex-direction: column;
}

.yt-segmented {
    display: inline-flex;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    overflow: hidden;
    background: var(--color-card-bg);
}

.yt-seg-btn {
    appearance: none;
    background: transparent;
    color: var(--color-text);
    border: 0;
    padding: 0.55rem 0.85rem;
    font-family: inherit;
    font-size: 0.85rem;
    cursor: pointer;
    transition: background 0.12s, color 0.12s;
}

.yt-seg-btn + .yt-seg-btn {
    border-left: 1px solid var(--color-border);
}

.yt-seg-btn:hover {
    background: var(--color-control-bg);
}

.yt-seg-btn[aria-pressed="true"] {
    background: var(--color-accent);
    color: #fff;
}

[data-theme="dark"] .yt-seg-btn[aria-pressed="true"] {
    background: var(--color-accent-medium, #3b82f6);
    color: var(--color-dark-bg);
}

.yt-controls input[type="search"],
.yt-controls select {
    width: 100%;
    padding: 0.55rem 0.75rem;
    background: var(--color-card-bg);
    color: var(--color-text);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    font-family: inherit;
    font-size: 0.95rem;
    transition: border-color 0.15s, box-shadow 0.15s;
}

.yt-controls input[type="search"]:focus,
.yt-controls select:focus {
    outline: none;
    border-color: var(--color-accent);
    box-shadow: 0 0 0 3px var(--color-accent-light);
}

.yt-controls select {
    cursor: pointer;
    min-width: 9rem;
}

/* Search + suggestion dropdown */

.yt-search-wrap {
    position: relative;
}

.yt-suggestions {
    position: absolute;
    top: calc(100% + 4px);
    left: 0;
    right: 0;
    z-index: 20;
    margin: 0;
    padding: 0.3rem 0;
    list-style: none;
    background: var(--color-card-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    box-shadow: 0 6px 24px rgba(0, 0, 0, 0.08);
    max-height: 22rem;
    overflow-y: auto;
}

[data-theme="dark"] .yt-suggestions {
    box-shadow: 0 6px 24px rgba(0, 0, 0, 0.5);
}

.yt-suggestion {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    padding: 0.45rem 0.7rem;
    cursor: pointer;
    font-size: 0.92rem;
    line-height: 1.3;
    transition: background 0.1s;
}

.yt-suggestion:hover,
.yt-suggestion.is-focus {
    background: var(--color-control-bg);
}

.yt-suggestion-type {
    flex: 0 0 auto;
    font-size: 0.65rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--color-text-muted);
    background: var(--color-control-bg);
    padding: 0.1rem 0.45rem;
    border-radius: 999px;
    min-width: 4.5rem;
    text-align: center;
}

.yt-suggestion.is-focus .yt-suggestion-type {
    background: var(--color-bg);
}

.yt-suggestion-label {
    flex: 1;
    min-width: 0;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.yt-suggestion-label mark {
    background: transparent;
    color: var(--color-accent);
    font-weight: 600;
}

[data-theme="dark"] .yt-suggestion-label mark {
    color: var(--color-accent-medium, #3b82f6);
}

/* Advanced search disclosure */

.yt-advanced {
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    background: var(--color-card-bg);
}

.yt-advanced[open] {
    background: transparent;
}

.yt-advanced-summary {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.55rem 0.75rem;
    cursor: pointer;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--color-text);
    list-style: none;
    user-select: none;
}

.yt-advanced-summary::-webkit-details-marker {
    display: none;
}

.yt-advanced-summary::before {
    content: '▸';
    color: var(--color-text-muted);
    font-size: 0.75rem;
    transition: transform 0.15s;
}

.yt-advanced[open] .yt-advanced-summary::before {
    transform: rotate(90deg);
}

.yt-advanced-label {
    flex: 1;
}

.yt-advanced-active {
    font-size: 0.7rem;
    color: var(--color-accent);
    font-weight: 600;
}

[data-theme="dark"] .yt-advanced-active {
    color: var(--color-accent-medium, #3b82f6);
}

.yt-advanced-active:empty {
    display: none;
}

.yt-clear-all {
    appearance: none;
    background: transparent;
    color: var(--color-text-muted);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    padding: 0.15rem 0.55rem;
    font-family: inherit;
    font-size: 0.75rem;
    font-weight: 500;
    cursor: pointer;
    transition: color 0.12s, border-color 0.12s, background 0.12s;
}

.yt-clear-all:hover {
    color: var(--color-error, #ef4444);
    border-color: var(--color-error, #ef4444);
    background: rgba(239, 68, 68, 0.08);
}

[data-theme="dark"] .yt-clear-all:hover {
    background: rgba(239, 68, 68, 0.15);
}

.yt-advanced-body {
    padding: 0.5rem 0.75rem 0.85rem;
    display: flex;
    flex-direction: column;
    gap: 0.85rem;
    border-top: 1px solid var(--color-border);
}

.yt-advanced-group {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.yt-advanced-group[hidden] {
    display: none;
}

.yt-chip-row {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
}

.yt-advanced-hint {
    font-size: 0.78rem;
    color: var(--color-text-muted);
    margin: 0;
    line-height: 1.4;
}

.yt-empty-inline {
    font-size: 0.82rem;
    color: var(--color-text-muted);
    margin: 0;
    padding: 0.25rem 0;
}

/* Tag filter chips */

.yt-tag-filter {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
}

.yt-tag-chip {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    padding: 0.35rem 0.7rem;
    background: var(--color-card-bg);
    color: var(--color-text);
    border: 1px solid var(--color-border);
    border-radius: 999px;
    font-family: inherit;
    font-size: 0.8rem;
    cursor: pointer;
    transition: background 0.12s, border-color 0.12s, color 0.12s;
}

.yt-tag-chip:hover {
    border-color: var(--color-accent);
}

.yt-tag-chip[aria-pressed="true"] {
    background: var(--color-accent);
    border-color: var(--color-accent);
    color: #fff;
}

[data-theme="dark"] .yt-tag-chip[aria-pressed="true"] {
    color: var(--color-dark-bg);
    background: var(--color-accent-medium, #3b82f6);
    border-color: var(--color-accent-medium, #3b82f6);
}

.yt-tag-count {
    font-size: 0.7rem;
    opacity: 0.7;
    font-variant-numeric: tabular-nums;
}

.yt-count {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    margin: 0;
}

/* Video grid */

.yt-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-xl);
    /* Keep the page height stable as filters shrink the result set.
       Without this, picking a tag shortens the page and the controls
       appear to jump up under the user's cursor. */
    min-height: 70vh;
    align-content: start;
}

.yt-list-grouped {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

.yt-channel-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.yt-channel-header {
    display: flex;
    align-items: baseline;
    gap: 0.6rem;
    border-bottom: 1px solid var(--color-border);
    padding: 0.4rem 0;
}

.yt-channel-name {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--color-text);
    transition: color 0.12s;
}

.yt-channel-name-link {
    text-decoration: none;
    color: inherit;
}

.yt-channel-name-link:hover .yt-channel-name {
    color: var(--color-accent);
    text-decoration: underline;
    text-decoration-thickness: 1px;
    text-underline-offset: 4px;
}

[data-theme="dark"] .yt-channel-name-link:hover .yt-channel-name {
    color: var(--color-accent-medium, #3b82f6);
}

.yt-channel-count {
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--color-text-muted);
    font-variant-numeric: tabular-nums;
}

.yt-channel-cards {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: var(--spacing-md);
}

.yt-channel-see-all {
    align-self: flex-start;
    margin-top: 0.25rem;
    font-size: 0.85rem;
    color: var(--color-accent);
    text-decoration: none;
    padding: 0.25rem 0;
    transition: color 0.12s, transform 0.12s;
}

.yt-channel-see-all:hover {
    text-decoration: underline;
    transform: translateX(2px);
}

[data-theme="dark"] .yt-channel-see-all {
    color: var(--color-accent-medium, #3b82f6);
}

.yt-card {
    display: flex;
    flex-direction: column;
    background: var(--color-card-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    overflow: hidden;
    text-decoration: none;
    color: inherit;
    transition: transform 0.15s, border-color 0.15s, box-shadow 0.15s;
}

.yt-card:hover {
    transform: translateY(-2px);
    border-color: var(--color-accent);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}

[data-theme="dark"] .yt-card:hover {
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.4);
}

.yt-card-thumb {
    position: relative;
    aspect-ratio: 16 / 9;
    background: #000;
    overflow: hidden;
}

.yt-card-thumb img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
    transition: filter 0.15s, opacity 0.15s;
}

/* Dim thumbnails in dark mode so the bright YouTube previews don't dominate
   the card UI; full color returns on hover so the user can identify videos
   they're looking at closely. */
[data-theme="dark"] .yt-card-thumb img {
    opacity: 0.75;
}

[data-theme="dark"] .yt-card:hover .yt-card-thumb img {
    opacity: 1;
}

/* Bump the card body a half-step brighter in dark mode so title + channel
   text reads with more contrast against the page background. */
[data-theme="dark"] .yt-card {
    background: #2a3543;
}

.yt-card-duration {
    position: absolute;
    right: 0.5rem;
    bottom: 0.5rem;
    background: rgba(0, 0, 0, 0.8);
    color: #fff;
    font-size: 0.75rem;
    padding: 0.15rem 0.4rem;
    border-radius: var(--radius-sm);
    font-variant-numeric: tabular-nums;
}

.yt-card-body {
    padding: 0.85rem 1rem 1rem;
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
    flex: 1;
}

.yt-card-title {
    font-size: 1rem;
    font-weight: 600;
    line-height: 1.3;
    margin: 0;
}

.yt-card-channel {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    margin: 0;
}

.yt-card-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
    align-items: center;
    margin-top: auto;
    padding-top: 0.4rem;
}

.yt-card-tags {
    display: inline-flex;
    flex-wrap: wrap;
    gap: 0.3rem;
}

/* Tag pill */

.yt-tag {
    display: inline-block;
    padding: 0.15rem 0.5rem;
    background: var(--color-control-bg);
    color: var(--color-text-muted);
    border-radius: 999px;
    font-size: 0.72rem;
    font-family: var(--font-mono);
    line-height: 1.5;
}

a.yt-tag-link {
    text-decoration: none;
    transition: background 0.12s, color 0.12s;
}

a.yt-tag-link:hover {
    background: var(--color-accent);
    color: #fff;
}

[data-theme="dark"] a.yt-tag-link:hover {
    background: var(--color-accent-medium, #3b82f6);
    color: var(--color-dark-bg);
}

button.yt-card-tag {
    font-family: var(--font-mono);
    cursor: pointer;
    border: 1px solid transparent;
    transition: background 0.12s, color 0.12s, border-color 0.12s;
}

button.yt-card-tag:hover {
    background: var(--color-accent);
    color: #fff;
    border-color: var(--color-accent);
}

button.yt-card-tag.is-active {
    background: var(--color-accent);
    color: #fff;
    border-color: var(--color-accent);
}

[data-theme="dark"] button.yt-card-tag:hover,
[data-theme="dark"] button.yt-card-tag.is-active {
    background: var(--color-accent-medium, #3b82f6);
    color: var(--color-dark-bg);
    border-color: var(--color-accent-medium, #3b82f6);
}

/* Depth badge */

.yt-depth {
    display: inline-block;
    padding: 0.15rem 0.55rem;
    border-radius: 999px;
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    line-height: 1.5;
}

.yt-depth-foundational {
    background: rgba(16, 185, 129, 0.15);
    color: #047857;
}

.yt-depth-applied {
    background: rgba(37, 99, 235, 0.15);
    color: #1d4ed8;
}

.yt-depth-reflective {
    background: rgba(168, 85, 247, 0.15);
    color: #7c3aed;
}

[data-theme="dark"] .yt-depth-foundational {
    color: #6ee7b7;
}

[data-theme="dark"] .yt-depth-applied {
    color: #bfdbfe;
}

[data-theme="dark"] .yt-depth-reflective {
    color: #d8b4fe;
}

.yt-loading,
.yt-empty {
    grid-column: 1 / -1;
    color: var(--color-text-muted);
    text-align: center;
    padding: var(--spacing-lg);
}

/* ===========================================
   Per-video page
   =========================================== */

.yt-video-page {
    max-width: 880px;
    margin: 0 auto;
}

.yt-breadcrumb {
    margin: var(--spacing-sm) 0 var(--spacing-md);
    font-size: 0.85rem;
    color: var(--color-text-muted);
}

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

.yt-breadcrumb a:hover {
    text-decoration: underline;
}

.yt-breadcrumb-current {
    color: var(--color-text);
}

.yt-breadcrumb span[aria-hidden] {
    margin: 0 0.4rem;
}

.yt-video-hero {
    /* This gap should match the section-to-section gap below (a yt-section's
       margin-bottom). Both are --spacing-lg; the apparent inequality came
       from the <header> below carrying a browser-default margin that stacked
       on top of this one — see .yt-video-header reset. */
    margin-bottom: var(--spacing-lg);
}

.yt-video-header {
    /* The site's layout.css applies `header { padding: var(--spacing-md) 0 }`
       to every <header>. That padding-bottom stacked inside .yt-video-hero on
       top of the hero's own margin-bottom, inflating the gap above the first
       section's divider. Zero both so the hero's margin-bottom is the only
       contributor — matching the section-to-section gap below it. */
    margin: 0;
    padding: 0;
}

.yt-embed {
    aspect-ratio: 16 / 9;
    width: 100%;
    background: #000;
    border-radius: var(--radius-md);
    overflow: hidden;
    margin-bottom: var(--spacing-md);
}

.yt-embed iframe {
    width: 100%;
    height: 100%;
    border: 0;
    display: block;
}

.yt-video-header h1 {
    font-size: 1.75rem;
    line-height: 1.2;
    margin: 0 0 0.5rem;
}

.yt-video-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
    align-items: center;
    color: var(--color-text-muted);
    font-size: 0.95rem;
    margin: 0 0 0.65rem;
}

.yt-channel {
    color: var(--color-text);
    font-weight: 500;
}

a.yt-channel-link {
    text-decoration: none;
    transition: color 0.12s;
}

a.yt-channel-link:hover {
    color: var(--color-accent);
    text-decoration: underline;
    text-decoration-thickness: 1px;
    text-underline-offset: 3px;
}

[data-theme="dark"] a.yt-channel-link:hover {
    color: var(--color-accent-medium, #3b82f6);
}

.yt-sep {
    color: var(--color-border);
}

.yt-tags-row {
    display: flex;
    flex-wrap: wrap;
    gap: 0.35rem;
    margin: 0 0 0.65rem;
}

.yt-domain-trail {
    margin: 0 0 0.65rem;
    font-size: 0.85rem;
    color: var(--color-text-muted);
}

.yt-domain-trail:empty {
    display: none;
}

.yt-domain-link {
    color: var(--color-text);
    text-decoration: none;
    border-bottom: 1px dotted var(--color-border);
    transition: color 0.12s, border-color 0.12s;
}

.yt-domain-link:hover {
    color: var(--color-accent);
    border-bottom-color: var(--color-accent);
}

[data-theme="dark"] .yt-domain-link:hover {
    color: var(--color-accent-medium, #3b82f6);
    border-bottom-color: var(--color-accent-medium, #3b82f6);
}

.yt-citekey-link {
    color: var(--color-accent);
    text-decoration: none;
    border-bottom: 1px dotted var(--color-accent);
    transition: color 0.12s, border-bottom-style 0.12s;
}

.yt-citekey-link:hover {
    border-bottom-style: solid;
}

[data-theme="dark"] .yt-citekey-link {
    color: var(--color-accent-medium, #3b82f6);
    border-bottom-color: var(--color-accent-medium, #3b82f6);
}

.yt-watch-on-yt {
    margin: 0;
    font-size: 0.9rem;
}

.yt-watch-on-yt a {
    color: var(--color-accent);
    text-decoration: none;
}

.yt-watch-on-yt a:hover {
    text-decoration: underline;
}

/* Sections */

.yt-section {
    margin-bottom: var(--spacing-lg);
    padding-top: var(--spacing-sm);
    border-top: 1px solid var(--color-border);
}

.yt-section h2 {
    font-size: 1.15rem;
    margin: 0 0 var(--spacing-sm);
}

.yt-prose {
    font-family: var(--font-serif);
    font-size: 1.05rem;
    line-height: 1.65;
}

.yt-prose p {
    margin: 0 0 0.85rem;
}

.yt-prose p:last-child {
    margin-bottom: 0;
}

.yt-prose code {
    font-family: var(--font-mono);
    font-size: 0.92em;
    padding: 0.1em 0.35em;
    background: var(--color-control-bg);
    border-radius: var(--radius-sm);
}

/* Questions */

.yt-questions-intro {
    font-size: 0.92rem;
    color: var(--color-text-muted);
    margin: 0 0 var(--spacing-sm);
}

.yt-questions {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 0.85rem;
}

.yt-questions li {
    padding: 0.85rem 1rem;
    background: #fafbfc;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    line-height: 1.55;
    font-family: var(--font-serif);
}

/* The question row (number + text + bloom badge) lays out horizontally;
   the answer reveal sits below it inside the same <li>. */
.yt-q-row {
    display: flex;
    align-items: flex-start;
    gap: 0.5rem;
}

.yt-question-answer {
    margin-top: 0.5rem;
    /* Override the course-answer 1.5rem left indent — video-page questions
       don't have the hanging indent that course quiz items use. */
    margin-left: 0;
    /* The yt-course-answer styles handle the rest (Show/Hide answer pill,
       expanded background, prose typography). */
}

.yt-q-text {
    flex: 1;
    min-width: 0;
}

[data-theme="dark"] .yt-questions li {
    background: var(--color-card-bg);
}

.yt-q-num {
    font-family: var(--font-mono);
    font-weight: 600;
    color: var(--color-accent);
    flex-shrink: 0;
}

[data-theme="dark"] .yt-q-num {
    color: var(--color-accent-medium, #3b82f6);
}

/* Before you watch — Prerequisites + Learning outcomes side by side */

.yt-before-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-md);
}

.yt-before-group {
    background: #fafbfc;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    padding: 0.85rem 1rem 1rem;
}

[data-theme="dark"] .yt-before-group {
    background: var(--color-card-bg);
}

.yt-before-heading {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--color-text-muted);
    margin: 0 0 0.55rem;
}

.yt-before-list {
    margin: 0;
    padding-left: 1.2rem;
    list-style: disc;
    line-height: 1.55;
    font-family: var(--font-serif);
}

.yt-before-list li {
    margin-bottom: 0.35rem;
}

.yt-before-list li:last-child {
    margin-bottom: 0;
}

/* Watch for — clickable timestamps into YouTube */

.yt-watch-for-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 0.55rem;
}

.yt-watch-for-list li {
    display: grid;
    grid-template-columns: auto 1fr;
    gap: 0.65rem;
    align-items: baseline;
    line-height: 1.55;
    font-family: var(--font-serif);
}

.yt-watch-for-time {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--color-accent);
    text-decoration: none;
    padding: 0.1rem 0.45rem;
    background: var(--color-control-bg);
    border-radius: var(--radius-sm);
    min-width: 3rem;
    text-align: center;
    transition: background 0.12s, color 0.12s;
}

.yt-watch-for-time:hover {
    background: var(--color-accent);
    color: #fff;
}

[data-theme="dark"] .yt-watch-for-time {
    color: var(--color-accent-medium, #3b82f6);
}

[data-theme="dark"] .yt-watch-for-time:hover {
    background: var(--color-accent-medium, #3b82f6);
    color: var(--color-dark-bg);
}

.yt-bloom {
    flex-shrink: 0;
    align-self: center;
    font-family: var(--font-mono);
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-text-muted);
    background: var(--color-control-bg);
    padding: 0.15rem 0.55rem;
    border-radius: 999px;
}

[data-theme="dark"] .yt-bloom {
    background: var(--color-bg);
}

.yt-q-text {
    /* Keeps the question prose visually distinct from the leading badges */
}

.yt-questions code {
    font-family: var(--font-mono);
    font-size: 0.92em;
    padding: 0.1em 0.35em;
    background: var(--color-control-bg);
    border-radius: var(--radius-sm);
}

/* Related videos */

.yt-related-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: var(--spacing-sm);
}

.yt-related-card {
    display: flex;
    flex-direction: column;
    background: var(--color-card-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    overflow: hidden;
    text-decoration: none;
    color: inherit;
    transition: transform 0.15s, border-color 0.15s;
}

.yt-related-card:hover {
    transform: translateY(-2px);
    border-color: var(--color-accent);
}

.yt-related-thumb {
    aspect-ratio: 16 / 9;
    background: #000;
    overflow: hidden;
}

.yt-related-thumb img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
}

.yt-related-info {
    padding: 0.6rem 0.75rem 0.75rem;
}

.yt-related-title {
    font-size: 0.92rem;
    font-weight: 600;
    line-height: 1.3;
    margin-bottom: 0.25rem;
}

.yt-related-meta {
    font-size: 0.78rem;
    color: var(--color-text-muted);
}

/* Mobile */

@media (max-width: 640px) {
    .yt-video-header h1 {
        font-size: 1.35rem;
    }
    .yt-control-row {
        flex-direction: column;
        align-items: stretch;
    }
    .yt-search-label,
    .yt-depth-label,
    .yt-sort-label,
    .yt-view-toggle {
        flex: 1 1 auto;
    }
    .yt-segmented {
        width: 100%;
    }
    .yt-seg-btn {
        flex: 1;
    }
}

/* ===========================================
   Course pages
   =========================================== */

.yt-course-page {
    max-width: 880px;
    margin: 0 auto;
}

.yt-course-header {
    margin-bottom: var(--spacing-md);
}

.yt-course-eyebrow {
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--color-text-muted);
    margin: 0 0 0.4rem;
}

.yt-course-header h1 {
    font-size: 2rem;
    line-height: 1.15;
    margin: 0 0 0.6rem;
}

.yt-course-description {
    font-size: 1.05rem;
    line-height: 1.5;
    color: var(--color-text-muted);
    margin: 0 0 0.7rem;
    font-family: var(--font-serif);
}

.yt-course-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
    align-items: center;
    font-size: 0.9rem;
    color: var(--color-text-muted);
    margin: 0;
}

.yt-course-meta-item {
    font-variant-numeric: tabular-nums;
}

/* Module sections — slightly stronger separation than ordinary yt-section */

.yt-course-module {
    padding-top: var(--spacing-md);
}

.yt-course-module > h2 {
    font-size: 1.35rem;
    margin-bottom: var(--spacing-sm);
}

/* Video item: card on top, prose below */

.yt-course-video {
    margin: var(--spacing-sm) 0 var(--spacing-md);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.yt-course-video-card {
    display: grid;
    grid-template-columns: 200px 1fr;
    gap: 1rem;
    background: #fafbfc;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    overflow: hidden;
    text-decoration: none;
    color: inherit;
    transition: transform 0.15s, border-color 0.15s, box-shadow 0.15s;
}

[data-theme="dark"] .yt-course-video-card {
    background: var(--color-card-bg);
}

.yt-course-video-card:hover {
    transform: translateY(-1px);
    border-color: var(--color-accent);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.06);
}

.yt-course-video-thumb {
    position: relative;
    aspect-ratio: 16 / 9;
    background: #000;
    overflow: hidden;
}

.yt-course-video-thumb img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
}

.yt-course-video-body {
    padding: 0.7rem 1rem 0.7rem 0;
    display: flex;
    flex-direction: column;
    gap: 0.3rem;
    justify-content: center;
}

.yt-course-video-title {
    font-size: 1rem;
    font-weight: 600;
    line-height: 1.3;
    margin: 0;
}

.yt-course-video-channel {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    margin: 0;
}

.yt-course-video-meta {
    display: flex;
    gap: 0.4rem;
    align-items: center;
    margin-top: 0.2rem;
}

.yt-course-video-card-missing {
    grid-template-columns: 1fr;
    padding: 0.85rem 1rem;
}

.yt-course-video-missing {
    color: var(--color-error);
    font-style: italic;
}

/* Connecting prose: a soft inline note between videos */

.yt-course-connecting {
    margin: var(--spacing-sm) 0;
    padding-left: 1rem;
    border-left: 3px solid var(--color-border);
}

.yt-course-connecting-label {
    display: block;
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--color-text-muted);
    margin-bottom: 0.25rem;
}

/* Quiz blocks */

.yt-course-quiz {
    margin-top: var(--spacing-md);
    padding: var(--spacing-sm) var(--spacing-sm) 0.6rem;
    background: #fafbfc;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
}

[data-theme="dark"] .yt-course-quiz {
    background: var(--color-card-bg);
}

.yt-course-quiz-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-text);
    margin: 0 0 0.6rem;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--color-border);
}

.yt-course-quiz-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 0.85rem;
}

.yt-course-quiz-item {
    padding: 0.4rem 0;
}

.yt-course-quiz-head {
    display: flex;
    gap: 0.5rem;
    align-items: flex-start;
    margin-bottom: 0.5rem;
    line-height: 1.5;
    font-family: var(--font-serif);
}

.yt-course-quiz-num {
    font-family: var(--font-mono);
    font-weight: 600;
    color: var(--color-accent);
    flex-shrink: 0;
}

[data-theme="dark"] .yt-course-quiz-num {
    color: var(--color-accent-medium, #3b82f6);
}

.yt-course-quiz-text {
    flex: 1;
    min-width: 0;
}

.yt-course-qtype {
    flex-shrink: 0;
    align-self: center;
}

.yt-course-choices {
    list-style: none;
    padding: 0 0 0 1.5rem;
    margin: 0 0 0.5rem;
    display: flex;
    flex-direction: column;
    gap: 0.3rem;
    font-family: var(--font-serif);
    line-height: 1.45;
}

.yt-course-choice-letter {
    font-family: var(--font-mono);
    font-weight: 600;
    color: var(--color-text-muted);
    margin-right: 0.3rem;
}

/* Collapsible answer */

.yt-course-answer {
    margin-left: 1.5rem;
    padding: 0.4rem 0;
}

.yt-course-answer summary {
    list-style: none;
    cursor: pointer;
    display: inline-block;
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--color-accent);
    padding: 0.2rem 0.6rem;
    border: 1px solid var(--color-accent);
    border-radius: 999px;
    transition: background 0.12s, color 0.12s;
    user-select: none;
}

.yt-course-answer summary::-webkit-details-marker {
    display: none;
}

.yt-course-answer summary::before {
    content: 'Show answer';
}

.yt-course-answer[open] summary::before {
    content: 'Hide answer';
}

.yt-course-answer summary:hover {
    background: var(--color-accent);
    color: #fff;
}

[data-theme="dark"] .yt-course-answer summary {
    color: var(--color-accent-medium, #3b82f6);
    border-color: var(--color-accent-medium, #3b82f6);
}

[data-theme="dark"] .yt-course-answer summary:hover {
    background: var(--color-accent-medium, #3b82f6);
    color: var(--color-dark-bg);
}

.yt-course-answer[open] {
    background: var(--color-control-bg);
    border-radius: var(--radius-sm);
    padding: 0.5rem 0.85rem 0.65rem;
    margin-top: 0.4rem;
}

.yt-course-answer[open] .yt-prose {
    margin-top: 0.5rem;
    font-size: 0.95rem;
}

/* Final assessment */

.yt-course-final {
    margin-top: var(--spacing-lg);
    padding-top: var(--spacing-md);
    border-top: 2px solid var(--color-border);
}

.yt-course-final h2 {
    font-size: 1.35rem;
}

/* Mobile */

@media (max-width: 640px) {
    .yt-course-video-card {
        grid-template-columns: 1fr;
    }
    .yt-course-video-body {
        padding: 0.6rem 0.85rem 0.85rem;
    }
    .yt-course-header h1 {
        font-size: 1.5rem;
    }
}

/* ===========================================
   Courses section on the YouTube University index
   =========================================== */

/* On the YouTube University index, tighten the gap between hero and the
   Courses teaser. The global .hero rule applies 4rem of bottom margin which
   is too generous when the teaser sits right below. */
.hero:has(+ .yt-courses-section),
.hero:has(+ .yt-search-hint) {
    margin-bottom: var(--spacing-md);
}

.yt-courses-section {
    margin: 0 0 var(--spacing-sm);
}

.yt-courses-header {
    margin-bottom: 0.25rem;
}

.yt-courses-header h2 {
    font-size: 1.15rem;
    margin: 0 0 0.25rem;
}

.yt-courses-blurb {
    font-size: 0.9rem;
    color: var(--color-text-muted);
    margin: 0;
}

.yt-courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--spacing-sm);
}

.yt-course-card {
    display: flex;
    flex-direction: column;
    gap: 0.45rem;
    padding: 0.85rem 1rem 1rem;
    background: #fafbfc;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    text-decoration: none;
    color: inherit;
    transition: transform 0.15s, border-color 0.15s, box-shadow 0.15s;
}

[data-theme="dark"] .yt-course-card {
    background: var(--color-card-bg);
}

.yt-course-card:hover {
    transform: translateY(-1px);
    border-color: var(--color-accent);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.06);
}

.yt-course-card-head {
    display: flex;
    align-items: baseline;
    gap: 0.5rem;
}

.yt-course-card-num {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--color-text-muted);
    background: var(--color-control-bg);
    padding: 0.1rem 0.45rem;
    border-radius: 999px;
}

.yt-course-card-title {
    flex: 1;
    font-size: 1rem;
    font-weight: 600;
    line-height: 1.25;
    margin: 0;
}

.yt-course-card-status {
    font-size: 0.65rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--color-text-muted);
    background: var(--color-control-bg);
    padding: 0.1rem 0.45rem;
    border-radius: 999px;
    align-self: center;
}

.yt-course-card-desc {
    font-size: 0.9rem;
    line-height: 1.45;
    color: var(--color-text-muted);
    margin: 0;
    font-family: var(--font-serif);
}

.yt-course-card-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
    align-items: center;
    font-size: 0.78rem;
    color: var(--color-text-muted);
    margin: 0;
    font-variant-numeric: tabular-nums;
}

/* Interactive multiple-choice quiz options */

.yt-course-choices-interactive {
    list-style: none;
    padding: 0;
    margin: 0 0 0.6rem;
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.yt-course-choices-interactive li {
    margin: 0;
}

.yt-course-choice-btn {
    width: 100%;
    text-align: left;
    display: flex;
    gap: 0.5rem;
    align-items: flex-start;
    padding: 0.55rem 0.85rem;
    background: var(--color-card-bg);
    color: var(--color-text);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    font-family: var(--font-serif);
    font-size: 0.95rem;
    line-height: 1.45;
    cursor: pointer;
    transition: background 0.12s, border-color 0.12s, transform 0.12s;
}

.yt-course-choice-btn:hover {
    border-color: var(--color-accent);
    background: var(--color-control-bg);
}

[data-theme="dark"] .yt-course-choice-btn:hover {
    border-color: var(--color-accent-medium, #3b82f6);
}

.yt-course-choice-btn:focus-visible {
    outline: 2px solid var(--color-accent);
    outline-offset: 2px;
}

.yt-course-choice-btn.is-correct {
    background: rgba(16, 185, 129, 0.1);
    border-color: var(--color-success, #10b981);
    color: var(--color-text);
}

.yt-course-choice-btn.is-incorrect {
    background: rgba(239, 68, 68, 0.1);
    border-color: var(--color-error, #ef4444);
    color: var(--color-text);
}

[data-theme="dark"] .yt-course-choice-btn.is-correct {
    background: rgba(16, 185, 129, 0.2);
}

[data-theme="dark"] .yt-course-choice-btn.is-incorrect {
    background: rgba(239, 68, 68, 0.2);
}

.yt-course-choice-btn .yt-course-choice-letter {
    flex-shrink: 0;
    font-family: var(--font-mono);
    font-weight: 600;
    color: var(--color-text-muted);
}

.yt-course-choice-btn.is-correct .yt-course-choice-letter::after {
    content: ' ✓';
    color: var(--color-success, #10b981);
}

.yt-course-choice-btn.is-incorrect .yt-course-choice-letter::after {
    content: ' ✗';
    color: var(--color-error, #ef4444);
}

.yt-course-choice-text {
    flex: 1;
    min-width: 0;
}

/* Per-choice explanation panel */

.yt-course-explanation {
    margin-top: 0.5rem;
    padding: 0.75rem 1rem 0.6rem;
    background: var(--color-control-bg);
    border-radius: var(--radius-sm);
    font-family: var(--font-serif);
    font-size: 0.95rem;
    line-height: 1.5;
    position: relative;
}

.yt-course-explanation[hidden] {
    display: none;
}

.yt-course-explanation-verdict {
    font-family: var(--font-sans);
    font-size: 0.85rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    margin: 0 0 0.4rem;
}

.yt-course-explanation-verdict.is-correct {
    color: var(--color-success, #10b981);
}

.yt-course-explanation-verdict.is-incorrect {
    color: var(--color-error, #ef4444);
}

.yt-course-explanation-body {
    margin: 0;
}

.yt-course-explanation-body p {
    margin: 0;
}

.yt-course-reset {
    margin-top: 0.6rem;
    appearance: none;
    background: transparent;
    color: var(--color-text-muted);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    padding: 0.25rem 0.7rem;
    font-family: inherit;
    font-size: 0.78rem;
    cursor: pointer;
    transition: background 0.12s, color 0.12s, border-color 0.12s;
}

.yt-course-reset:hover {
    background: var(--color-card-bg);
    color: var(--color-text);
    border-color: var(--color-accent);
}

/* "Coming soon" badge inside the Courses header */

.yt-courses-soon {
    font-family: var(--font-mono);
    font-size: 0.65rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--color-text-muted);
    background: var(--color-control-bg);
    padding: 0.15rem 0.5rem;
    border-radius: 999px;
    vertical-align: 0.2em;
    margin-left: 0.4rem;
}

/* Brief search-functionality hint above the controls */

.yt-search-hint {
    margin: 0 0 var(--spacing-sm);
    padding: 0.6rem 0.85rem;
    background: var(--color-control-bg);
    border-left: 3px solid var(--color-accent);
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    line-height: 1.5;
    color: var(--color-text-muted);
}

.yt-search-hint p {
    margin: 0;
}

[data-theme="dark"] .yt-search-hint {
    border-left-color: var(--color-accent-medium, #3b82f6);
}