html {
	scrollbar-gutter: stable;
}

:root {
	--bg: #f8f8f8;
	--fg: #222;
	--muted: #444;
	--faint: #777;
	--link: #0055cc;
	--col-half: 410px;
}

html[data-theme="dark"] {
	--bg: #161616;
	--fg: #e8e8e8;
	--muted: #b6b6b6;
	--faint: #8a8a8a;
	--link: #6cb0ff;
}

body {
	position: relative;
	margin-top: 0;
	padding-top: 0;
	background: var(--bg);
	color: var(--fg);
	transition: background-color 0.2s ease, color 0.2s ease;
}

p { color: var(--muted); }
a { color: var(--link); }
.soon { color: var(--faint); font-style: italic; }

/*
 * .page-heading is the single sticky block.
 * Row 1: h1 (flex:1) + toggle
 * Row 2: .quicklinks strip (flex-basis:100% forces it to its own row)
 * Same layout on mobile and desktop — quicklinks is always a horizontal strip.
 */

.page-heading {
	position: sticky;
	top: 0;
	z-index: 15;
	display: flex;
	flex-wrap: wrap;
	align-items: center;
	padding-top: 0.4rem;
	background: var(--bg);
	transition: background-color 0.2s ease;
}

.page-heading h1 {
	flex: 1;
	min-width: 0;
	margin: 0;
	font-size: clamp(2rem, 8vw, 3rem);
}

#theme-toggle {
	position: static;
	flex-shrink: 0;
	width: 2rem;
	height: 2rem;
	padding: 0;
	border: 1px solid var(--faint);
	border-radius: 50%;
	background: transparent;
	color: var(--fg);
	cursor: pointer;
	font-size: 1rem;
	display: inline-flex;
	align-items: center;
	justify-content: center;
	font-family: system-ui, sans-serif;
}

#theme-toggle:hover {
	border-color: var(--link);
	color: var(--link);
}

/* back arrow — CSS chevron, no Unicode glyph metrics */
.ql-back {
	display: inline-flex;
	align-items: center;
	justify-content: center;
	align-self: center;
	flex-shrink: 0;
	text-decoration: none;
	color: var(--link);
	width: 1.5rem;
	height: 1.5rem;
}

.ql-back::before {
	content: '';
	display: block;
	width: 0.42rem;
	height: 0.42rem;
	border-left: 2px solid currentColor;
	border-bottom: 2px solid currentColor;
	transform: rotate(45deg) translate(15%, 0);
}

.ql-back:hover { opacity: 0.7; }

/* "play" button in quicklinks — reverse of link colors */
.ql-play {
	display: inline-block;
	padding: 0.1rem 0.55rem;
	background: var(--link);
	color: var(--bg) !important;
	border-radius: 3px;
	text-decoration: none;
	font-size: 0.9rem;
	line-height: 1.5;
}
.ql-play:hover { opacity: 0.8; }

/* Mobile: quicklinks is the second sticky row, directly below the heading */
.quicklinks {
	flex-basis: 100%;
	height: 2.5rem;
	display: flex;
	align-items: center;
	gap: 0.5rem;
	padding: 0;
	border-top: 1px solid var(--faint);
	overflow-x: auto;
}

.quicklinks ul {
	display: flex;
	align-items: center;
	gap: 1.25rem;
	margin: 0;
	padding: 0;
	list-style: none;
	overflow-x: auto;
	flex: 1;
	min-width: 0;
}

.quicklinks li {
	font-size: 0.9rem;
	white-space: nowrap;
	margin: 0;
}

/* ─── Thumbnail side strips ─────────────────────────────────────────────── */

/* Base: all thumbnail strips */
.thumb-col {
	position: fixed;
	z-index: 10;
	display: flex;
	flex-direction: column;
	gap: 3px;
	overflow: hidden;
	top: 0;
	bottom: 0;
}

.thumb-col img {
	display: block;
	width: 100%;
	flex-shrink: 0;
	object-fit: cover;
	aspect-ratio: 1;
	border-radius: 2px;
	cursor: default;
	pointer-events: none;
}

/* Left/top/bottom strips hidden on mobile */
.thumb-left, .thumb-top, .thumb-bottom { display: none; }
/* top strip never shown */
.thumb-top { display: none !important; }

/* Right strip on mobile: its own scroll container, independent of the page */
.thumb-right {
	right: 4px;
	width: 56px;
	overflow-y: auto;
	overscroll-behavior: contain; /* don't chain scroll to the page */
	-webkit-overflow-scrolling: touch;
	scrollbar-width: none;
}
.thumb-right::-webkit-scrollbar { display: none; }

/* Inner wrapper: plain flex column (images are duplicated for the cyclic loop) */
.thumb-right .thumb-scroll {
	display: flex;
	flex-direction: column;
	gap: 3px;
}

/* ─── Desktop: thumbnail frame + heading below top strip ─────────────────── */
@media (min-width: 1240px) {
	:root {
		--thumb-size: calc((100vh - 12 * 3px) / 13);
	}

	body {
		margin-top: 0;
		padding-top: 0;
	}

	.page-heading { top: 0; }

	/* Side strips: 8px gap from the content column */
	.thumb-left {
		display: flex;
		right: calc(50% + var(--col-half) + 8px);
		left: auto;
		top: 0;
		bottom: 0;
		width: var(--thumb-size);
	}
	.thumb-right {
		left: calc(50% + var(--col-half) + 8px);
		right: auto;
		top: 0;
		bottom: 0;
		width: var(--thumb-size);
		overflow: hidden; /* static frame on desktop, no scrolling */
	}

	.thumb-left img, .thumb-right img {
		flex: 0 0 var(--thumb-size);
		width: var(--thumb-size);
		height: var(--thumb-size);
		aspect-ratio: unset;
		flex-shrink: 0;
	}

}