/* Learn Pi — Obsidian vault tutorial (inspired by learn-claude-code progression) */
@font-face {
	font-family: "Inter";
	src: url("assets/fonts/inter-latin-400-normal.woff2") format("woff2");
	font-style: normal;
	font-weight: 400;
	font-display: swap;
}

@font-face {
	font-family: "Inter";
	src: url("assets/fonts/inter-latin-500-normal.woff2") format("woff2");
	font-style: normal;
	font-weight: 500;
	font-display: swap;
}

@font-face {
	font-family: "Inter";
	src: url("assets/fonts/inter-latin-600-normal.woff2") format("woff2");
	font-style: normal;
	font-weight: 600;
	font-display: swap;
}

@font-face {
	font-family: "Inter";
	src: url("assets/fonts/inter-latin-700-normal.woff2") format("woff2");
	font-style: normal;
	font-weight: 700;
	font-display: swap;
}

@font-face {
	font-family: "JetBrains Mono";
	src: url("assets/fonts/jetbrains-mono-latin-400-normal.woff2") format("woff2");
	font-style: normal;
	font-weight: 400;
	font-display: swap;
}

@font-face {
	font-family: "JetBrains Mono";
	src: url("assets/fonts/jetbrains-mono-latin-500-normal.woff2") format("woff2");
	font-style: normal;
	font-weight: 500 700;
	font-display: swap;
}

:root {
	--bg: #1e1e1e;
	--bg-secondary: #252525;
	--bg-tertiary: #2a2a2a;
	--bg-hover: #2e2e2e;
	--bg-active: #333333;
	--border: rgba(255, 255, 255, 0.08);
	--border-strong: rgba(255, 255, 255, 0.12);
	--text: #dcddde;
	--text-muted: #b0b0b0;
	--text-faint: #8d8d8d;
	--accent: #7c6df0;
	--accent-hover: #8b7cf7;
	--accent-solid: #6552c7;
	--accent-solid-hover: #5745b4;
	--accent-soft: rgba(124, 109, 240, 0.14);
	--accent-border: rgba(124, 109, 240, 0.35);
	--success: #68b984;
	--warning: #d4a017;
	--stage1: #5b8def;
	--stage2: #68b984;
	--stage3: #d4a017;
	--stage4: #e07a9a;
	--stage5: #9b7ed9;
	--stage6: #4db8c4;
	--radius: 6px;
	--radius-lg: 10px;
	--sidebar-w: 280px;
	--font: "Inter", "Segoe UI", system-ui, -apple-system, sans-serif;
	--font-mono: "JetBrains Mono", "Cascadia Code", "Fira Code", ui-monospace, monospace;
	--shadow: 0 8px 32px rgba(0, 0, 0, 0.35);
	--ease: cubic-bezier(0.22, 1, 0.36, 1);
	--nav-h: 48px;
	--content-w: 760px;
	color-scheme: dark;
}

[data-theme="light"] {
	--bg: #ffffff;
	--bg-secondary: #f7f7f7;
	--bg-tertiary: #f0f0f0;
	--bg-hover: #ebebeb;
	--bg-active: #e4e4e4;
	--border: rgba(0, 0, 0, 0.08);
	--border-strong: rgba(0, 0, 0, 0.12);
	--text: #2e2e2e;
	--text-muted: #595959;
	--text-faint: #707070;
	--accent: #6048bf;
	--accent-hover: #4f3aa5;
	--accent-solid: #6048bf;
	--accent-solid-hover: #4f3aa5;
	--accent-soft: rgba(112, 93, 207, 0.1);
	--accent-border: rgba(112, 93, 207, 0.3);
	--shadow: 0 8px 32px rgba(0, 0, 0, 0.08);
	color-scheme: light;
}

*,
*::before,
*::after {
	box-sizing: border-box;
	margin: 0;
	padding: 0;
}

html {
	scroll-behavior: smooth;
}

body {
	font-family: var(--font);
	font-size: 15px;
	line-height: 1.7;
	color: var(--text);
	background: var(--bg);
	min-height: 100dvh;
	-webkit-font-smoothing: antialiased;
	overflow-x: hidden;
}

::selection {
	background: var(--accent-soft);
	color: var(--text);
}

a {
	color: var(--accent);
	text-decoration: none;
	transition: color 0.15s var(--ease);
}

a:hover {
	color: var(--accent-hover);
	text-decoration: underline;
	text-underline-offset: 3px;
}

code {
	font-family: var(--font-mono);
	font-size: 0.88em;
	background: var(--accent-soft);
	color: var(--accent);
	padding: 0.1em 0.4em;
	border-radius: 4px;
}

/* Layout */
.app {
	display: grid;
	grid-template-columns: var(--sidebar-w) minmax(0, 1fr);
	min-height: 100dvh;
	transition: grid-template-columns 0.22s var(--ease);
}

.app.sidebar-collapsed {
	grid-template-columns: 0 minmax(0, 1fr);
}

.sidebar {
	position: sticky;
	top: 0;
	height: 100dvh;
	background: var(--bg-secondary);
	border-right: 1px solid var(--border);
	display: flex;
	flex-direction: column;
	width: var(--sidebar-w);
	overflow: visible;
	z-index: 40;
	transition: transform 0.22s var(--ease), opacity 0.16s ease;
}

.app.sidebar-collapsed .sidebar {
	transform: translateX(-100%);
	opacity: 0;
	pointer-events: none;
}

.sidebar-header {
	display: flex;
	align-items: center;
	gap: 10px;
	padding: 14px 16px;
	border-bottom: 1px solid var(--border);
	min-height: var(--nav-h);
}

.logo-copy {
	min-width: 0;
	flex: 1;
}

.sidebar-collapse {
	width: 28px;
	height: 28px;
	padding: 0;
	background: transparent;
	font-size: 20px;
	line-height: 1;
}

.sidebar-resizer {
	position: absolute;
	top: 0;
	right: -4px;
	width: 8px;
	height: 100%;
	cursor: col-resize;
	touch-action: none;
	z-index: 2;
}

.sidebar-resizer::after {
	content: "";
	position: absolute;
	top: 0;
	bottom: 0;
	left: 3px;
	width: 2px;
	background: var(--accent);
	opacity: 0;
	transition: opacity 0.15s;
}

.sidebar-resizer:hover::after,
.sidebar-resizer:focus-visible::after,
body.sidebar-resizing .sidebar-resizer::after {
	opacity: 0.8;
}

body.sidebar-resizing {
	cursor: col-resize;
	user-select: none;
}

body.sidebar-resizing .app {
	transition: none;
}

.logo {
	width: 28px;
	height: 28px;
	border-radius: 6px;
	background: var(--accent-soft);
	border: 1px solid var(--accent-border);
	display: grid;
	place-items: center;
	font-weight: 700;
	font-size: 13px;
	color: var(--accent);
	flex-shrink: 0;
}

.logo-text {
	font-weight: 600;
	font-size: 14px;
	letter-spacing: -0.01em;
}

.logo-sub {
	font-size: 11px;
	color: var(--text-faint);
	margin-top: 1px;
}

.progress-bar-wrap {
	padding: 10px 14px 4px;
}

.progress-jump {
	display: block;
	width: 100%;
	padding: 8px 10px;
	border: 1px solid transparent;
	border-radius: var(--radius);
	background: transparent;
	color: inherit;
	font: inherit;
	text-align: left;
	cursor: pointer;
	transition: background 0.12s, border-color 0.12s;
}

.progress-jump:hover {
	background: var(--bg-hover);
	border-color: var(--border);
}

.progress-jump:focus-visible {
	outline: 2px solid var(--accent);
	outline-offset: 2px;
}

.progress-meta {
	display: flex;
	justify-content: space-between;
	font-size: 11px;
	color: var(--text-faint);
	margin-bottom: 6px;
}

.progress-track {
	height: 4px;
	background: var(--bg);
	border-radius: 99px;
	overflow: hidden;
}

.progress-fill {
	height: 100%;
	width: 0%;
	background: var(--accent);
	border-radius: 99px;
	transition: width 0.35s var(--ease);
}

.progress-next {
	margin-top: 6px;
	font-size: 11px;
	color: var(--accent);
	font-weight: 500;
	line-height: 1.35;
	overflow: hidden;
	text-overflow: ellipsis;
	white-space: nowrap;
}

.sidebar-search {
	margin: 8px 12px;
	position: relative;
}

.sidebar-search input {
	width: 100%;
	background: var(--bg);
	border: 1px solid var(--border);
	border-radius: var(--radius);
	padding: 8px 12px 8px 32px;
	color: var(--text);
	font: inherit;
	font-size: 13px;
	outline: none;
	transition: border-color 0.15s, box-shadow 0.15s;
}

.sidebar-search input::placeholder {
	color: var(--text-faint);
}

.sidebar-search input:focus {
	border-color: var(--accent-border);
	box-shadow: 0 0 0 3px var(--accent-soft);
}

.sidebar-search .icon {
	position: absolute;
	left: 10px;
	top: 50%;
	transform: translateY(-50%);
	color: var(--text-faint);
	pointer-events: none;
	display: flex;
}

.nav-section {
	padding: 4px 8px 12px;
	flex: 1;
	overflow-y: auto;
}

.nav-label {
	font-size: 11px;
	font-weight: 600;
	text-transform: uppercase;
	letter-spacing: 0.06em;
	color: var(--text-faint);
	padding: 10px 10px 4px;
}

.nav-item {
	display: flex;
	align-items: center;
	gap: 8px;
	width: 100%;
	padding: 6px 10px;
	border: none;
	background: transparent;
	color: var(--text-muted);
	font: inherit;
	font-size: 13px;
	border-radius: var(--radius);
	cursor: pointer;
	text-align: left;
	transition: background 0.12s, color 0.12s;
}

.nav-item:hover {
	background: var(--bg-hover);
	color: var(--text);
}

.nav-item.active {
	background: var(--accent-soft);
	color: var(--accent);
	font-weight: 500;
}

.nav-item .sid {
	font-family: var(--font-mono);
	font-size: 11px;
	color: var(--text-faint);
	min-width: 28px;
	flex-shrink: 0;
}

.nav-item.active .sid {
	color: var(--accent);
}

.nav-item .check {
	margin-left: auto;
	font-size: 11px;
	color: var(--success);
	opacity: 0;
}

.nav-item.done .check {
	opacity: 1;
}

.sidebar-footer {
	padding: 12px;
	border-top: 1px solid var(--border);
	display: flex;
	gap: 6px;
	flex-wrap: wrap;
}

.icon-btn {
	display: inline-flex;
	align-items: center;
	justify-content: center;
	gap: 6px;
	padding: 6px 10px;
	border: 1px solid var(--border);
	background: var(--bg);
	color: var(--text-muted);
	border-radius: var(--radius);
	font: inherit;
	font-size: 12px;
	cursor: pointer;
	transition: background 0.12s, color 0.12s, border-color 0.12s;
}

.icon-btn:hover {
	background: var(--bg-hover);
	color: var(--text);
	border-color: var(--border-strong);
}

.icon-btn:disabled {
	opacity: 0.38;
	cursor: not-allowed;
}

.kbd {
	font-family: var(--font-mono);
	font-size: 10px;
	padding: 1px 5px;
	border-radius: 3px;
	background: var(--bg-tertiary);
	border: 1px solid var(--border);
	color: var(--text-faint);
}

.main {
	min-width: 0;
	display: flex;
	flex-direction: column;
}

.topbar {
	position: sticky;
	top: 0;
	z-index: 30;
	display: flex;
	align-items: center;
	justify-content: space-between;
	gap: 12px;
	padding: 0 28px;
	height: var(--nav-h);
	background: color-mix(in srgb, var(--bg) 88%, transparent);
	backdrop-filter: blur(12px);
	-webkit-backdrop-filter: blur(12px);
	border-bottom: 1px solid var(--border);
}

.breadcrumb {
	display: flex;
	align-items: center;
	gap: 6px;
	font-size: 13px;
	color: var(--text-muted);
	min-width: 0;
}

.breadcrumb span.current {
	color: var(--text);
	font-weight: 500;
	overflow: hidden;
	text-overflow: ellipsis;
	white-space: nowrap;
}

.topbar-actions {
	display: flex;
	align-items: center;
	gap: 8px;
	flex-shrink: 0;
}

.menu-toggle {
	display: inline-flex;
	width: 30px;
	height: 30px;
	padding: 0;
	flex-shrink: 0;
}

.content {
	flex: 1;
	padding: 36px 28px 100px;
	max-width: calc(var(--content-w) + 56px);
	width: 100%;
	margin: 0 auto;
}

.view {
	display: none;
	animation: fadeIn 0.28s var(--ease);
}

.view.active {
	display: block;
}

@keyframes fadeIn {
	from {
		opacity: 0;
		transform: translateY(6px);
	}
	to {
		opacity: 1;
		transform: none;
	}
}

/* Typography */
h1 {
	font-size: clamp(1.65rem, 3.5vw, 2.1rem);
	font-weight: 650;
	letter-spacing: -0.03em;
	line-height: 1.25;
	margin-bottom: 12px;
}

h2 {
	font-size: 1.2rem;
	font-weight: 600;
	letter-spacing: -0.02em;
	margin: 2.25rem 0 0.75rem;
	padding-bottom: 0.4rem;
	border-bottom: 1px solid var(--border);
}

h3 {
	font-size: 1.02rem;
	font-weight: 600;
	margin: 1.4rem 0 0.5rem;
}

h1,
h2,
h3 {
	scroll-margin-top: calc(var(--nav-h) + 18px);
}

.heading-anchor {
	display: inline-block;
	margin-left: 0.45em;
	color: var(--text-faint);
	font-family: var(--font-mono);
	font-size: 0.72em;
	font-weight: 500;
	opacity: 0;
	text-decoration: none;
	transition: opacity 0.15s, color 0.15s;
}

h2:hover .heading-anchor,
h3:hover .heading-anchor,
.heading-anchor:focus-visible {
	opacity: 1;
}

.heading-anchor:hover {
	color: var(--accent);
	text-decoration: none;
}

/* Contextual heading outline */
.page-outline {
	position: fixed;
	top: calc(var(--nav-h) + 20px);
	right: max(14px, env(safe-area-inset-right));
	z-index: 38;
	width: min(220px, calc(100vw - 32px));
	max-height: calc(100dvh - var(--nav-h) - 40px);
	overflow: hidden auto;
	background: color-mix(in srgb, var(--bg-secondary) 94%, transparent);
	border: 1px solid var(--border-strong);
	border-radius: var(--radius-lg);
	box-shadow: var(--shadow);
	backdrop-filter: blur(12px);
	transform: translateX(calc(100% + 24px));
	visibility: hidden;
	transition: transform 0.2s var(--ease), visibility 0.2s;
}

.page-outline[hidden] {
	display: none !important;
}

.page-outline.open {
	transform: none;
	visibility: visible;
}

.page-outline-header {
	position: sticky;
	top: 0;
	display: flex;
	align-items: center;
	justify-content: space-between;
	gap: 8px;
	padding: 9px 10px 9px 12px;
	background: var(--bg-secondary);
	border-bottom: 1px solid var(--border);
	font-family: var(--font-mono);
	font-size: 10px;
	font-weight: 600;
	letter-spacing: 0.06em;
	text-transform: uppercase;
	color: var(--text-faint);
}

.page-outline-close {
	width: 26px;
	height: 26px;
	padding: 0;
	font-size: 16px;
}

.page-outline-list {
	display: grid;
	gap: 2px;
	padding: 7px;
	overscroll-behavior: contain;
}

.page-outline-link {
	display: block;
	padding: 6px 8px;
	border-radius: var(--radius);
	color: var(--text-muted);
	font-size: 12px;
	line-height: 1.35;
}

.page-outline-link.level-h3 {
	padding-left: 18px;
	font-size: 11px;
	color: var(--text-faint);
}

.page-outline-link:hover,
.page-outline-link.active {
	background: var(--accent-soft);
	color: var(--accent);
	text-decoration: none;
}

@media (min-width: 1500px) {
	.outline-toggle {
		display: none;
	}

	.page-outline:not([hidden]) {
		transform: none;
		visibility: visible;
		box-shadow: none;
	}

	.page-outline-close {
		display: none;
	}
}

.lead {
	font-size: 1.05rem;
	color: var(--text-muted);
	line-height: 1.75;
	max-width: 62ch;
	margin-bottom: 1.25rem;
}

p {
	margin-bottom: 1rem;
	max-width: 68ch;
}

.meta-row {
	display: flex;
	flex-wrap: wrap;
	gap: 8px;
	margin-bottom: 1.25rem;
}

.badge {
	display: inline-flex;
	align-items: center;
	gap: 5px;
	padding: 3px 10px;
	font-size: 12px;
	font-weight: 500;
	border-radius: 999px;
	background: var(--bg-tertiary);
	border: 1px solid var(--border);
	color: var(--text-muted);
}

.badge.accent {
	background: var(--accent-soft);
	border-color: var(--accent-border);
	color: var(--accent);
}

.badge.ok {
	color: var(--success);
	border-color: color-mix(in srgb, var(--success) 30%, transparent);
	background: color-mix(in srgb, var(--success) 10%, transparent);
}

/* Motto (learn-claude-code style) */
.motto {
	margin: 1.25rem 0 1.5rem;
	padding: 16px 18px;
	border-left: 3px solid var(--accent);
	background: var(--bg-secondary);
	border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
}

.motto .label {
	font-size: 11px;
	font-weight: 600;
	text-transform: uppercase;
	letter-spacing: 0.06em;
	color: var(--text-faint);
	margin-bottom: 6px;
}

.motto blockquote {
	font-size: 1.05rem;
	font-style: italic;
	color: var(--text);
	line-height: 1.55;
	border: none;
	margin: 0;
	padding: 0;
}

.motto .explain {
	margin: 8px 0 0;
	font-size: 13px;
	font-style: normal;
	color: var(--text-muted);
}

.quote {
	margin: 1.25rem 0;
	padding: 16px 18px;
	border-left: 3px solid var(--accent);
	background: var(--bg-secondary);
	border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
	font-size: 15px;
	color: var(--text-muted);
	font-style: italic;
}

.quote strong {
	font-style: normal;
	color: var(--text);
}

/* Mermaid diagrams */
.diagram-wrap {
	margin: 1.25rem 0 1.5rem;
	border: 1px solid var(--border);
	border-radius: var(--radius-lg);
	background: var(--bg-secondary);
	overflow: hidden;
}

.diagram-header {
	display: flex;
	align-items: center;
	justify-content: space-between;
	gap: 10px;
	padding: 6px 8px 6px 14px;
	border-bottom: 1px solid var(--border);
	font-size: 12px;
	font-weight: 500;
	color: var(--text-faint);
	letter-spacing: 0.02em;
}

.diagram-toggle,
.tutorial-gallery-toggle {
	display: inline-flex;
	align-items: center;
	gap: 8px;
	min-width: 0;
	padding: 4px 0;
	border: 0;
	background: transparent;
	color: inherit;
	font: inherit;
	font-weight: inherit;
	letter-spacing: inherit;
	cursor: pointer;
	text-align: left;
}

.section-chevron {
	display: inline-block;
	color: var(--accent);
	font-size: 11px;
	transition: transform 0.18s var(--ease);
}

[aria-expanded="false"] > .section-chevron {
	transform: rotate(-90deg);
}

.diagram-header-actions {
	display: flex;
	align-items: center;
	gap: 6px;
}

.diagram-expand {
	background: transparent;
}

.diagram-host {
	padding: 16px 12px;
	overflow-x: auto;
	display: flex;
	justify-content: center;
	min-height: 120px;
}

.diagram-host .mermaid {
	margin: 0 auto;
	background: transparent;
}

.diagram-host svg {
	max-width: 100%;
	height: auto;
}

.diagram-host[hidden],
.tutorial-gallery-grid[hidden] {
	display: none !important;
}

.diagram-error {
	margin: 0;
	padding: 12px;
	font-size: 13px;
	color: var(--warning);
	max-width: none;
}

/* Pattern box */
.pattern {
	margin: 1.25rem 0;
	padding: 16px 18px;
	background: var(--bg-secondary);
	border: 1px solid var(--border);
	border-radius: var(--radius-lg);
	font-family: var(--font-mono);
	font-size: 12.5px;
	line-height: 1.65;
	color: var(--text-muted);
	overflow-x: auto;
	white-space: pre;
}

.pattern .hi {
	color: var(--accent);
}

/* Cards / grids */
.grid-2 {
	display: grid;
	grid-template-columns: repeat(2, 1fr);
	gap: 12px;
	margin: 1.25rem 0;
}

.grid-3 {
	display: grid;
	grid-template-columns: repeat(3, 1fr);
	gap: 12px;
	margin: 1.25rem 0;
}

.card {
	background: var(--bg-secondary);
	border: 1px solid var(--border);
	border-radius: var(--radius-lg);
	padding: 14px 16px;
	transition: border-color 0.15s, background 0.15s, transform 0.2s var(--ease);
	color: inherit;
	font: inherit;
	text-align: left;
}

button.card {
	width: 100%;
	cursor: pointer;
	display: block;
}

.card:hover {
	border-color: var(--border-strong);
	background: var(--bg-tertiary);
}

.card.interactive {
	cursor: pointer;
}

.card.interactive:hover {
	border-color: var(--accent-border);
	transform: translateY(-1px);
}

.card:focus-visible {
	outline: 2px solid var(--accent);
	outline-offset: 2px;
}

.card-title {
	font-weight: 600;
	font-size: 14px;
	margin-bottom: 6px;
	display: flex;
	align-items: center;
	gap: 8px;
}

.card-desc {
	font-size: 13px;
	color: var(--text-muted);
	line-height: 1.55;
	margin: 0;
	max-width: none;
}

.card-meta {
	margin-top: 8px;
	font-size: 11px;
	color: var(--text-faint);
	font-family: var(--font-mono);
}

/* Lesson cards on home */
.lesson-card {
	display: flex;
	gap: 12px;
	align-items: flex-start;
	padding: 12px 14px;
	border: 1px solid var(--border);
	border-radius: var(--radius-lg);
	background: var(--bg-secondary);
	cursor: pointer;
	text-align: left;
	width: 100%;
	font: inherit;
	color: inherit;
	transition: border-color 0.15s, background 0.15s, transform 0.2s var(--ease);
}

.lesson-card:hover {
	border-color: var(--accent-border);
	background: var(--bg-tertiary);
	transform: translateY(-1px);
}

.lesson-card .num {
	font-family: var(--font-mono);
	font-size: 12px;
	font-weight: 600;
	color: var(--accent);
	min-width: 32px;
	padding-top: 2px;
}

.lesson-card .body {
	flex: 1;
	min-width: 0;
}

.lesson-card .title {
	font-weight: 600;
	font-size: 14px;
	margin-bottom: 2px;
}

.lesson-card .mot {
	font-size: 12px;
	color: var(--text-muted);
	font-style: italic;
	line-height: 1.45;
}

.lesson-card.done {
	border-color: color-mix(in srgb, var(--success) 35%, transparent);
}

.lesson-card.done .num {
	color: var(--success);
}

/* Stage path */
.stage-grid {
	display: grid;
	gap: 12px;
	margin: 1.25rem 0;
}

.stage {
	border: 1px solid var(--border);
	border-radius: var(--radius-lg);
	padding: 14px 16px;
	background: var(--bg-secondary);
	border-left-width: 3px;
	transition: border-color 0.15s, box-shadow 0.15s;
}

.stage.stage-current {
	box-shadow: 0 0 0 1px var(--accent-border);
}

.stage.stage-complete {
	opacity: 0.92;
}

.stage-toggle {
	display: flex;
	align-items: center;
	justify-content: space-between;
	gap: 10px;
	width: 100%;
	padding: 0;
	border: none;
	background: none;
	color: inherit;
	font: inherit;
	cursor: pointer;
	text-align: left;
}

.stage-toggle h3 {
	margin: 0;
}

.stage-progress {
	font-family: var(--font-mono);
	font-size: 11px;
	padding: 2px 8px;
	border-radius: 999px;
	background: var(--bg);
	border: 1px solid var(--border);
	color: var(--text-faint);
	flex-shrink: 0;
}

.stage-progress.complete {
	color: var(--success);
	border-color: color-mix(in srgb, var(--success) 35%, transparent);
}

.stage.collapsed ul {
	display: none;
}

.stage.collapsed .stage-toggle h3::after {
	content: " ▸";
	color: var(--text-faint);
	font-weight: 400;
}

.continue-hint {
	margin: -0.5rem 0 1rem;
	font-size: 13px;
	color: var(--text-muted);
	max-width: 62ch;
}

.nav-filter-empty {
	padding: 12px 10px;
	font-size: 12px;
	color: var(--text-faint);
	display: flex;
	flex-direction: column;
	align-items: flex-start;
	gap: 8px;
}

.nav-filter-empty[hidden] {
	display: none !important;
}

.stage[data-stage="1"] {
	border-left-color: var(--stage1);
}
.stage[data-stage="2"] {
	border-left-color: var(--stage2);
}
.stage[data-stage="3"] {
	border-left-color: var(--stage3);
}
.stage[data-stage="4"] {
	border-left-color: var(--stage4);
}
.stage[data-stage="5"] {
	border-left-color: var(--stage5);
}
.stage[data-stage="6"] {
	border-left-color: var(--stage6);
}

.stage h3 {
	margin: 0 0 8px;
	font-size: 14px;
}

.stage ul {
	list-style: none;
	display: grid;
	gap: 4px;
}

.stage li {
	font-size: 13px;
	color: var(--text-muted);
}

.stage li button {
	background: none;
	border: none;
	color: var(--accent);
	font: inherit;
	font-size: 13px;
	cursor: pointer;
	padding: 0;
}

.stage li button:hover {
	text-decoration: underline;
}

/* Callout */
.callout {
	display: flex;
	gap: 12px;
	padding: 14px 16px;
	border-radius: var(--radius-lg);
	background: var(--accent-soft);
	border: 1px solid var(--accent-border);
	margin: 1.25rem 0;
	font-size: 14px;
}

.callout.warn {
	background: color-mix(in srgb, var(--warning) 12%, transparent);
	border-color: color-mix(in srgb, var(--warning) 35%, transparent);
}

.callout-icon {
	flex-shrink: 0;
	color: var(--accent);
	font-size: 16px;
	line-height: 1.4;
}

.callout.warn .callout-icon {
	color: var(--warning);
}

.callout p {
	margin: 0;
	color: var(--text);
	max-width: none;
}

/* Code */
.code-block {
	position: relative;
	background: var(--bg-secondary);
	border: 1px solid var(--border);
	border-radius: var(--radius-lg);
	margin: 1rem 0 1.5rem;
	overflow: hidden;
}

.code-block-header {
	display: flex;
	align-items: center;
	justify-content: space-between;
	padding: 6px 12px;
	border-bottom: 1px solid var(--border);
	font-size: 12px;
	color: var(--text-faint);
}

.code-block pre {
	padding: 14px 16px;
	overflow-x: auto;
	font-family: var(--font-mono);
	font-size: 12.5px;
	line-height: 1.6;
	color: var(--text);
	margin: 0;
}

.code-block .comment {
	color: var(--text-faint);
}

.code-block .cmd {
	color: var(--accent);
}

.copy-btn.copied {
	color: var(--success);
	border-color: color-mix(in srgb, var(--success) 40%, transparent);
}

/* Concept chips */
.concepts {
	display: flex;
	flex-wrap: wrap;
	gap: 6px;
	margin: 0.75rem 0 1.25rem;
}

.concept {
	font-family: var(--font-mono);
	font-size: 11px;
	padding: 3px 8px;
	border-radius: 4px;
	background: var(--bg-tertiary);
	border: 1px solid var(--border);
	color: var(--text-muted);
}

/* Feature list */
.feature-list {
	list-style: none;
	display: grid;
	gap: 6px;
	margin: 1rem 0;
}

.feature-list li {
	display: grid;
	grid-template-columns: 20px 1fr;
	gap: 10px;
	padding: 8px 10px;
	border-radius: var(--radius);
	border: 1px solid transparent;
	font-size: 14px;
}

.feature-list li:hover {
	background: var(--bg-secondary);
	border-color: var(--border);
}

.feature-list .mark {
	color: var(--accent);
	font-weight: 600;
}

/* Table */
.table-wrap {
	overflow-x: auto;
	margin: 1rem 0 1.5rem;
	border: 1px solid var(--border);
	border-radius: var(--radius-lg);
}

table {
	width: 100%;
	border-collapse: collapse;
	font-size: 13.5px;
}

th,
td {
	padding: 10px 14px;
	text-align: left;
	border-bottom: 1px solid var(--border);
}

th {
	background: var(--bg-secondary);
	font-weight: 600;
	font-size: 12px;
	color: var(--text-muted);
	text-transform: uppercase;
	letter-spacing: 0.04em;
}

tr:last-child td {
	border-bottom: none;
}

tr:hover td {
	background: var(--bg-secondary);
}

td code {
	font-size: 12px;
}

/* Lesson nav footer */
.lesson-nav {
	display: flex;
	justify-content: space-between;
	gap: 12px;
	margin-top: 2.5rem;
	padding-top: 1.25rem;
	border-top: 1px solid var(--border);
	flex-wrap: wrap;
}

.lesson-nav .btn {
	flex: 1;
	min-width: 140px;
}

.lesson-actions {
	display: flex;
	gap: 8px;
	flex-wrap: wrap;
	margin-top: 1.25rem;
}

.btn {
	display: inline-flex;
	align-items: center;
	justify-content: center;
	gap: 6px;
	padding: 8px 14px;
	border-radius: var(--radius);
	font: inherit;
	font-size: 13px;
	font-weight: 500;
	cursor: pointer;
	border: 1px solid var(--border);
	background: var(--bg-secondary);
	color: var(--text);
	text-decoration: none;
	transition: background 0.12s, border-color 0.12s, color 0.12s;
}

.btn:hover {
	background: var(--bg-hover);
	border-color: var(--border-strong);
	text-decoration: none;
	color: var(--text);
}

.btn.primary {
	background: var(--accent-solid);
	border-color: var(--accent-solid);
	color: #fff;
}

.btn.primary:hover {
	background: var(--accent-solid-hover);
	border-color: var(--accent-solid-hover);
	color: #fff;
}

.btn.ghost {
	background: transparent;
}

.btn.done-btn.is-done {
	color: var(--success);
	border-color: color-mix(in srgb, var(--success) 40%, transparent);
}

details {
	margin: 1rem 0;
	border: 1px solid var(--border);
	border-radius: var(--radius-lg);
	background: var(--bg-secondary);
	overflow: hidden;
}

summary {
	padding: 12px 14px;
	cursor: pointer;
	font-weight: 500;
	font-size: 14px;
	list-style: none;
	display: flex;
	align-items: center;
	gap: 8px;
}

summary::-webkit-details-marker {
	display: none;
}

summary::before {
	content: "▸";
	color: var(--accent);
	font-size: 12px;
	transition: transform 0.15s;
}

details[open] summary::before {
	transform: rotate(90deg);
}

details .inner {
	padding: 0 14px 14px;
	border-top: 1px solid var(--border);
	padding-top: 12px;
}

.page-footer {
	margin-top: 2.5rem;
	padding-top: 1.25rem;
	border-top: 1px solid var(--border);
	font-size: 12px;
	color: var(--text-faint);
}

.link-strip {
	display: flex;
	flex-wrap: wrap;
	gap: 10px;
	margin: 1.25rem 0;
}

/* Palette */
.palette-backdrop {
	position: fixed;
	inset: 0;
	background: rgba(0, 0, 0, 0.55);
	backdrop-filter: blur(4px);
	z-index: 100;
	display: none;
	align-items: flex-start;
	justify-content: center;
	padding-top: min(18vh, 120px);
}

.palette-backdrop.open {
	display: flex;
	animation: fadeIn 0.15s var(--ease);
}

.palette {
	width: min(520px, calc(100vw - 32px));
	background: var(--bg-secondary);
	border: 1px solid var(--border-strong);
	border-radius: 12px;
	box-shadow: var(--shadow);
	overflow: hidden;
}

.palette-heading {
	display: flex;
	align-items: center;
	justify-content: space-between;
	gap: 12px;
	padding: 9px 14px;
	border-bottom: 1px solid var(--border);
	font-size: 12px;
	font-weight: 600;
	color: var(--text-muted);
}

.palette-hint {
	font-size: 10px;
	font-weight: 400;
	color: var(--text-faint);
}

.palette input {
	width: 100%;
	padding: 14px 16px;
	border: none;
	border-bottom: 1px solid var(--border);
	background: transparent;
	color: var(--text);
	font: inherit;
	font-size: 15px;
	outline: none;
}

.palette input::placeholder {
	color: var(--text-faint);
}

.palette-list {
	max-height: 360px;
	overflow-y: auto;
	padding: 6px;
}

.palette-item {
	display: grid;
	grid-template-columns: minmax(0, 1fr) minmax(120px, 42%);
	align-items: center;
	gap: 12px;
	width: 100%;
	padding: 10px 12px;
	border: none;
	background: transparent;
	border-radius: var(--radius);
	color: var(--text);
	font: inherit;
	font-size: 13.5px;
	cursor: pointer;
	text-align: left;
}

.palette-item-main {
	display: flex;
	align-items: center;
	gap: 8px;
	min-width: 0;
}

.palette-item-kind {
	min-width: 38px;
	padding: 2px 5px;
	border: 1px solid var(--border);
	border-radius: 4px;
	font-family: var(--font-mono);
	font-size: 9px;
	font-weight: 500;
	text-align: center;
	color: var(--text-faint);
}

.palette-item-title {
	overflow: hidden;
	text-overflow: ellipsis;
	white-space: nowrap;
}

.palette-item:hover,
.palette-item.focused {
	background: var(--accent-soft);
	color: var(--accent);
}

.palette-item .hint {
	font-size: 11px;
	color: var(--text-faint);
	line-height: 1.35;
	display: -webkit-box;
	-webkit-line-clamp: 2;
	-webkit-box-orient: vertical;
	overflow: hidden;
}

.palette-empty {
	padding: 20px;
	text-align: center;
	color: var(--text-faint);
	font-size: 13px;
}

.sidebar-overlay {
	display: none;
	position: fixed;
	inset: 0;
	background: rgba(0, 0, 0, 0.45);
	z-index: 35;
}

.sidebar-overlay.open {
	display: block;
}

ul.plain {
	margin: 0.75rem 0 1.25rem 1.2rem;
	color: var(--text-muted);
}

ul.plain li {
	margin-bottom: 0.4rem;
}

@media (max-width: 900px) {
	.app {
		grid-template-columns: 1fr;
	}

	.app.sidebar-collapsed {
		grid-template-columns: 1fr;
	}

	.sidebar {
		position: fixed;
		left: 0;
		top: 0;
		width: min(var(--sidebar-w), 88vw);
		transform: translateX(-100%);
		transition: transform 0.25s var(--ease);
		box-shadow: var(--shadow);
	}

	.app.sidebar-collapsed .sidebar {
		transform: translateX(-100%);
		opacity: 1;
		pointer-events: auto;
	}

	.sidebar.open,
	.app.sidebar-collapsed .sidebar.open {
		transform: none;
	}


	.sidebar-collapse,
	.sidebar-resizer {
		display: none;
	}

	.content {
		padding: 24px 16px 80px;
	}

	.topbar {
		padding: 0 14px;
	}

	.grid-2,
	.grid-3 {
		grid-template-columns: 1fr;
	}
}

/* Image tutorials */
.tutorial-gallery {
	margin: 1.25rem 0 1.5rem;
	border: 1px solid var(--border);
	border-radius: var(--radius-lg);
	background: var(--bg-secondary);
	overflow: hidden;
}

.tutorial-gallery-header {
	display: flex;
	align-items: center;
	justify-content: space-between;
	gap: 10px;
	padding: 8px 14px;
	border-bottom: 1px solid var(--border);
}

.tutorial-gallery-header .label {
	font-size: 12px;
	font-weight: 600;
	text-transform: uppercase;
	letter-spacing: 0.05em;
	color: var(--text-faint);
}

.tutorial-gallery-meta {
	font-size: 11px;
	font-family: var(--font-mono);
	color: var(--text-faint);
}

.tutorial-gallery-grid {
	display: grid;
	gap: 0;
}

.tutorial-figure {
	margin: 0;
	padding: 14px 16px 16px;
	border-bottom: 1px solid var(--border);
}

.tutorial-figure:last-child {
	border-bottom: none;
}

.tutorial-figure-frame {
	position: relative;
	border: 1px solid var(--border);
	border-radius: var(--radius);
	background: var(--bg);
	overflow: hidden;
	cursor: zoom-in;
	transition: border-color 0.15s, box-shadow 0.15s;
}

.tutorial-figure-frame:hover {
	border-color: var(--accent-border);
	box-shadow: 0 0 0 3px var(--accent-soft);
}

.tutorial-figure img {
	display: block;
	width: 100%;
	height: auto;
	max-height: min(420px, 55vh);
	object-fit: contain;
	background: var(--bg);
}

.tutorial-step {
	position: absolute;
	top: 8px;
	left: 8px;
	z-index: 1;
	font-size: 11px;
	font-weight: 600;
	padding: 3px 8px;
	border-radius: 999px;
	background: color-mix(in srgb, var(--bg) 88%, transparent);
	border: 1px solid var(--border);
	color: var(--accent);
	backdrop-filter: blur(6px);
}

.tutorial-figure figcaption {
	margin-top: 10px;
	font-size: 13px;
	color: var(--text-muted);
	line-height: 1.5;
}

/* Mid-article figures (manual HTML embed) */
.content > .tutorial-figure,
.view .tutorial-figure.inline {
	margin: 1.25rem 0;
}

/* Lightbox */
.lightbox {
	position: fixed;
	inset: 0;
	z-index: 200;
	display: flex;
	align-items: center;
	justify-content: center;
	padding: 24px;
	background: rgba(0, 0, 0, 0.78);
	backdrop-filter: blur(6px);
}

.lightbox[hidden] {
	display: none !important;
}

.lightbox-close {
	position: absolute;
	top: 16px;
	right: 16px;
	width: 40px;
	height: 40px;
	border: 1px solid var(--border-strong);
	border-radius: 99px;
	background: var(--bg-secondary);
	color: var(--text);
	font-size: 22px;
	line-height: 1;
	cursor: pointer;
}

.lightbox-close:hover {
	background: var(--bg-hover);
}

.lightbox-figure {
	margin: 0;
	max-width: min(1100px, 100%);
	max-height: 100%;
	display: flex;
	flex-direction: column;
	align-items: center;
	gap: 12px;
}

.lightbox-figure img {
	max-width: 100%;
	max-height: calc(100dvh - 100px);
	object-fit: contain;
	border-radius: var(--radius);
	box-shadow: var(--shadow);
	background: var(--bg);
}

.lightbox-figure figcaption {
	font-size: 13px;
	color: #ddd;
	text-align: center;
	max-width: 60ch;
}

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

/* Mermaid focus view */
.diagram-lightbox {
	position: fixed;
	inset: 0;
	z-index: 210;
	display: grid;
	grid-template-rows: auto minmax(0, 1fr);
	background: color-mix(in srgb, var(--bg) 94%, transparent);
	backdrop-filter: blur(12px);
}

.diagram-lightbox[hidden] {
	display: none !important;
}

.diagram-lightbox-bar {
	display: flex;
	align-items: center;
	justify-content: space-between;
	gap: 16px;
	min-height: 64px;
	padding: 10px 16px 10px 20px;
	background: var(--bg-secondary);
	border-bottom: 1px solid var(--border-strong);
}

.diagram-lightbox-kicker {
	font-family: var(--font-mono);
	font-size: 10px;
	letter-spacing: 0.08em;
	color: var(--accent);
}

.diagram-lightbox-title {
	font-size: 14px;
	font-weight: 600;
	color: var(--text);
}

.diagram-lightbox-actions {
	display: flex;
	align-items: center;
	gap: 6px;
	flex-shrink: 0;
}

.diagram-zoom-value {
	min-width: 58px;
	padding: 6px 8px;
	border: 1px solid var(--border);
	border-radius: var(--radius);
	background: var(--bg);
	color: var(--text-muted);
	font: 500 11px var(--font-mono);
	cursor: pointer;
}

.diagram-lightbox-close {
	margin-left: 6px;
	font-size: 18px;
}

.diagram-lightbox-canvas {
	min-width: 0;
	min-height: 0;
	overflow: auto;
	display: flex;
	align-items: center;
	padding: clamp(20px, 5vw, 64px);
	background-image: radial-gradient(circle, var(--border-strong) 1px, transparent 1px);
	background-size: 20px 20px;
}

.diagram-lightbox-stage {
	width: 100%;
	min-width: 100%;
	flex: 0 0 100%;
	margin: auto;
	display: flex;
	align-items: center;
	transition: width 0.18s var(--ease);
}

.diagram-lightbox-stage svg {
	display: block;
	width: var(--diagram-zoom, 100%) !important;
	max-width: none !important;
	height: auto !important;
	min-height: 0 !important;
	flex: 0 0 auto;
	margin: auto;
	transition: width 0.18s var(--ease);
}

@media (max-width: 620px) {
	.diagram-lightbox-bar {
		align-items: flex-start;
		padding: 10px 12px;
	}

	.diagram-lightbox-kicker {
		display: none;
	}

	.diagram-lightbox-title {
		max-width: 34vw;
		overflow: hidden;
		text-overflow: ellipsis;
		white-space: nowrap;
	}

	.diagram-lightbox-canvas {
		padding: 16px;
	}
}

/* Toast */
.toast {
	position: fixed;
	bottom: 24px;
	left: 50%;
	transform: translateX(-50%);
	z-index: 150;
	display: flex;
	align-items: center;
	gap: 12px;
	padding: 10px 14px;
	border-radius: 10px;
	background: var(--bg-tertiary);
	border: 1px solid var(--border-strong);
	box-shadow: var(--shadow);
	font-size: 13px;
	color: var(--text);
	max-width: min(420px, calc(100vw - 32px));
}

.toast[hidden] {
	display: none !important;
}

.toast-action {
	flex-shrink: 0;
	border: none;
	background: var(--accent-solid);
	color: #fff;
	font: inherit;
	font-size: 12px;
	font-weight: 600;
	padding: 6px 10px;
	border-radius: var(--radius);
	cursor: pointer;
}

.toast-action:hover {
	background: var(--accent-solid-hover);
}

/* A11y helpers */
.skip-link {
	position: absolute;
	left: -9999px;
	top: 8px;
	z-index: 300;
	padding: 8px 12px;
	background: var(--accent-solid);
	color: #fff;
	border-radius: var(--radius);
	font-weight: 600;
	font-size: 13px;
}

.skip-link:focus {
	left: 8px;
}

.visually-hidden {
	position: absolute;
	width: 1px;
	height: 1px;
	padding: 0;
	margin: -1px;
	overflow: hidden;
	clip: rect(0, 0, 0, 0);
	white-space: nowrap;
	border: 0;
}

:focus-visible {
	outline: 2px solid var(--accent);
	outline-offset: 2px;
}

.btn:focus-visible,
.icon-btn:focus-visible,
.nav-item:focus-visible,
.lesson-card:focus-visible {
	outline: 2px solid var(--accent);
	outline-offset: 2px;
}

.palette-backdrop[hidden] {
	display: none !important;
}

/* Shortcut reference */
.shortcuts-backdrop {
	position: fixed;
	inset: 0;
	z-index: 205;
	display: none;
	align-items: center;
	justify-content: center;
	padding: max(20px, env(safe-area-inset-top)) max(20px, env(safe-area-inset-right))
		max(20px, env(safe-area-inset-bottom)) max(20px, env(safe-area-inset-left));
	background: rgba(0, 0, 0, 0.58);
	backdrop-filter: blur(6px);
}

.shortcuts-backdrop.open {
	display: flex;
}

.shortcuts-backdrop[hidden] {
	display: none !important;
}

.shortcuts {
	width: min(520px, 100%);
	max-height: min(620px, 90dvh);
	overflow: auto;
	overscroll-behavior: contain;
	background: var(--bg-secondary);
	border: 1px solid var(--border-strong);
	border-radius: 12px;
	box-shadow: var(--shadow);
}

.shortcuts-header {
	display: flex;
	align-items: center;
	justify-content: space-between;
	gap: 12px;
	padding: 11px 12px 11px 16px;
	border-bottom: 1px solid var(--border);
	font-weight: 600;
}

.shortcuts-table td:first-child {
	width: 42%;
	white-space: nowrap;
}

/* Platform polish */
html {
	scroll-padding-top: calc(var(--nav-h) + 18px);
	overscroll-behavior-y: none;
}

:is(a, button, [role="button"], summary) {
	-webkit-tap-highlight-color: transparent;
	touch-action: manipulation;
}

:is(.progress-meta, .progress-next, .stage-progress, .badge, .tutorial-gallery-meta, .diagram-zoom-value) {
	font-variant-numeric: tabular-nums;
}

:is(h1, h2, h3, .card-title, .motto blockquote) {
	text-wrap: balance;
}

:is(p, li, figcaption, .card-desc) {
	text-wrap: pretty;
}

.sidebar {
	padding-top: env(safe-area-inset-top);
	padding-bottom: env(safe-area-inset-bottom);
}

.topbar {
	padding-left: max(28px, env(safe-area-inset-left));
	padding-right: max(28px, env(safe-area-inset-right));
}

.content {
	padding-bottom: calc(100px + env(safe-area-inset-bottom));
}

:is(.nav-section, .palette-list, .diagram-lightbox-canvas, .lightbox, .tutorial-gallery-grid) {
	overscroll-behavior: contain;
}

.lightbox {
	padding-top: max(24px, env(safe-area-inset-top));
	padding-right: max(24px, env(safe-area-inset-right));
	padding-bottom: max(24px, env(safe-area-inset-bottom));
	padding-left: max(24px, env(safe-area-inset-left));
}

.tutorial-figure-frame:focus-visible {
	outline: 2px solid var(--accent);
	outline-offset: 3px;
	border-color: var(--accent-border);
}

body.shortcuts-open {
	overflow: hidden;
}

@media (max-width: 900px) {
	.topbar {
		padding-left: max(14px, env(safe-area-inset-left));
		padding-right: max(14px, env(safe-area-inset-right));
	}

	.content {
		padding-bottom: calc(80px + env(safe-area-inset-bottom));
	}
}

@media (max-width: 620px) {
	.topbar-actions > .badge,
	.topbar-actions > a.btn {
		display: none;
	}

	.outline-toggle {
		padding-inline: 9px;
	}

	.palette-heading {
		align-items: flex-start;
		flex-direction: column;
		gap: 5px;
	}

	.palette-item {
		grid-template-columns: 1fr;
		gap: 4px;
	}

	.palette-item .hint {
		padding-left: 46px;
	}
}

@media print {
	:root {
		--bg: #ffffff;
		--bg-secondary: #ffffff;
		--text: #111111;
		--text-muted: #333333;
		--text-faint: #555555;
		--border: rgba(0, 0, 0, 0.2);
		--border-strong: rgba(0, 0, 0, 0.32);
		color-scheme: light;
	}

	body {
		font-size: 11pt;
		background: #fff;
		color: #111;
		overflow: visible;
	}

	.sidebar,
	.sidebar-overlay,
	.topbar,
	.page-outline,
	.palette-backdrop,
	.lightbox,
	.diagram-lightbox,
	.shortcuts-backdrop,
	.toast,
	.lesson-actions,
	.lesson-nav,
	.heading-anchor,
	.diagram-expand,
	.copy-btn {
		display: none !important;
	}

	.app,
	.app.sidebar-collapsed {
		display: block;
	}

	.content {
		max-width: none;
		padding: 0;
		margin: 0;
	}

	.view.active {
		display: block;
		animation: none;
	}

	.diagram-wrap,
	.tutorial-gallery,
	.code-block,
	.card,
	details,
	.callout,
	.motto {
		break-inside: avoid;
		box-shadow: none;
	}

	a[href^="http"]::after {
		content: " (" attr(href) ")";
		font-size: 0.8em;
		word-break: break-all;
	}
}

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