:root {
    color-scheme: light;
    --bg: #f4f7fb;
    --bg-soft: #e8eef7;
    --panel: #fff;
    --panel-soft: #eef4fb;
    --line: #d6e1ef;
    --line-strong: #b8c9df;
    --ink: #10233f;
    --ink-dim: #63738a;
    --accent: #2f6fed;
    --accent-strong: #2056bd;
    --accent-soft: #dce9ff;
    --mint: #1fae6b;
    --mint-strong: #168a56;
    --sage: #397b75;
    --honey: #e5a94f;
    --footer: #fff;
    --mono: 'DM Mono', ui-monospace, SFMono-Regular, Menlo, monospace;
    --sans: 'Manrope', ui-sans-serif, system-ui, sans-serif;
    --maxw: 1160px;
    --shadow: 0 16px 32px rgba(16, 35, 63, .09)
}

html[data-theme="dark"] {
    color-scheme: dark;
    --bg: #091a32;
    --bg-soft: #0d2340;
    --panel: #102744;
    --panel-soft: #132d4d;
    --line: #244260;
    --line-strong: #385979;
    --ink: #f5f8ff;
    --ink-dim: #aabbd0;
    --accent: #72a5ff;
    --accent-strong: #9fc2ff;
    --accent-soft: #1c3e6a;
    --mint: #22c47a;
    --mint-strong: #34d68f;
    --sage: #82c9bd;
    --honey: #f0c36d;
    --footer: #07162a;
    --shadow: 0 18px 40px rgba(4, 17, 38, .28)
}

* {
    box-sizing: border-box
}

html {
    scroll-behavior: smooth
}

body {
    margin: 0;
    background: var(--bg);
    color: var(--ink);
    font-family: var(--sans);
    font-size: 16px;
    line-height: 1.65;
    -webkit-font-smoothing: antialiased;
    transition: background .35s ease, color .35s ease
}

a {
    color: var(--accent-strong)
}

a:focus-visible,
button:focus-visible {
    outline: 3px solid var(--accent);
    outline-offset: 4px;
    border-radius: 8px
}

.wrap {
    max-width: var(--maxw);
    margin: 0 auto;
    padding: 0 32px
}

header {
    position: sticky;
    top: 0;
    z-index: 20;
    background: color-mix(in srgb, var(--bg) 90%, transparent);
    backdrop-filter: blur(16px);
    border-bottom: 1px solid color-mix(in srgb, var(--line) 82%, transparent);
    transition: background .35s ease, border-color .35s ease
}

.titlebar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 17px 0;
    gap: 18px
}

.mark {
    font: 600 13px var(--mono);
    letter-spacing: .02em;
    color: var(--ink);
    display: flex;
    align-items: center;
    gap: 10px;
    text-decoration: none
}

.mark .dot {
    width: 16px;
    height: 16px;
    border-radius: 6px;
    background: linear-gradient(135deg, var(--accent), var(--accent-strong));
    box-shadow: 0 0 0 5px var(--accent-soft), inset 0 1px 1px rgba(255, 255, 255, .35);
    transition: transform .25s ease, border-radius .25s ease
}

.mark:hover .dot {
    transform: scale(1.15) rotate(-6deg);
    border-radius: 9px
}

nav {
    display: flex;
    align-items: center;
    gap: 20px;
    font: 11px var(--mono);
    letter-spacing: .08em;
    text-transform: uppercase
}

nav a {
    color: var(--ink-dim);
    text-decoration: none;
    transition: color .2s ease
}

nav a:hover {
    color: var(--accent-strong)
}

.theme-toggle {
    border: 1px solid var(--line-strong);
    background: var(--panel);
    color: var(--ink);
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 7px 13px 7px 7px;
    border-radius: 999px;
    font: 600 11px var(--mono);
    cursor: pointer;
    transition: transform .2s ease, background .3s ease, border-color .2s ease, color .2s ease, box-shadow .2s ease
}

.theme-toggle:hover {
    transform: translateY(-2px);
    border-color: var(--accent);
    color: var(--accent-strong);
    box-shadow: 0 7px 16px color-mix(in srgb, var(--accent) 18%, transparent)
}

.theme-toggle:active {
    transform: translateY(0)
}

.theme-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 22px;
    height: 22px;
    border-radius: 50%;
    background: var(--accent-soft);
    color: var(--accent-strong);
    line-height: 1
}

.theme-label:after {
    content: 'Dark mode'
}

html[data-theme="dark"] .theme-label:after {
    content: 'Light mode'
}

footer {
    border-top: 1px solid var(--line);
    padding: 34px 0;
    background: var(--footer);
    transition: background .35s ease, border-color .35s ease
}

.footer-grid {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 20px;
    flex-wrap: wrap
}

.footer-links {
    display: flex;
    gap: 18px;
    flex-wrap: wrap;
    font: 12px var(--mono)
}

.footer-note {
    color: var(--ink-dim);
    font: 11px var(--mono);
    letter-spacing: .04em
}

.frame {
    background: var(--panel);
    border: 1px solid var(--line);
    border-radius: 14px;
    box-shadow: var(--shadow);
    transition: transform .25s ease, border-color .25s ease, box-shadow .25s ease
}

a.frame:hover {
    transform: translateY(-5px);
    border-color: var(--accent)
}

.page-head {
    padding: 56px 0 40px
}

.eyebrow {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    background: var(--accent-soft);
    color: var(--accent-strong);
    padding: 8px 13px;
    border-radius: 999px;
    font: 600 11px var(--mono);
    letter-spacing: .04em;
    margin-bottom: 18px
}

.eyebrow::before {
    content: '\2726';
    font-size: 14px
}

.page-head h1 {
    max-width: 820px;
    font-size: clamp(34px, 5.5vw, 54px);
    line-height: 1.05;
    letter-spacing: -0.05em;
    margin: 0 0 14px
}

.page-head p.lede {
    max-width: 640px;
    font-size: 16.5px;
    margin: 0;
    color: var(--ink-dim)
}

section.block {
    padding: 12px 0 76px;
    scroll-margin-top: 76px
}

.section-heading {
    display: flex;
    align-items: flex-end;
    justify-content: space-between;
    gap: 20px;
    margin-bottom: 20px
}

.section-heading h2 {
    font-size: 28px;
    line-height: 1.15;
    letter-spacing: -.05em;
    margin: 0
}

.section-heading p {
    margin: 0;
    color: var(--ink-dim);
    font-size: 13px
}

.lessons {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 16px
}

.lesson-card {
    min-height: 200px;
    padding: 23px 21px;
    display: flex;
    flex-direction: column;
    gap: 12px;
    text-decoration: none
}

.lc-top {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: 10px
}

.lc-title {
    display: flex;
    align-items: center;
    gap: 9px;
    min-width: 0
}

.lesson-card h3 {
    font-size: 15px;
    line-height: 1.35;
    font-weight: 700;
    letter-spacing: -0.01em;
    margin: 0
}

.lesson-card p {
    color: var(--ink-dim);
    font-size: 13px;
    line-height: 1.7;
    margin: 0
}

.number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    flex: 0 0 auto;
    width: 22px;
    height: 22px;
    border-radius: 999px;
    background: var(--accent-soft);
    color: var(--accent-strong);
    font: 700 10px var(--mono)
}

.stamp.planned {
    font: 700 10px var(--mono);
    letter-spacing: .08em;
    text-transform: uppercase;
    padding: 4px 8px;
    border-radius: 999px;
    background: color-mix(in srgb, var(--honey) 24%, var(--panel));
    color: color-mix(in srgb, var(--honey) 60%, var(--ink));
    white-space: nowrap
}

@media (max-width:800px) {
    .lessons {
        grid-template-columns: 1fr
    }
}