:root {
    --bg-accent: #dfe7ff;
    --panel: rgba(255, 255, 255, 0.96);
    --panel-strong: #ffffff;
    --panel-border: rgba(106, 90, 205, 0.16);
    --text: #1f2a44;
    --muted: #5f6f86;
    --accent: #6a5acd;
    --accent-dark: #5443c4;
    --accent-soft: rgba(106, 90, 205, 0.12);
    --radius: 8px;
    --sans: "Segoe UI", Tahoma, sans-serif;
}

[data-theme="dark"] {
    --bg-accent: #07130f;
    --panel: rgba(13, 22, 18, 0.96);
    --panel-strong: #080f0c;
    --panel-border: rgba(0, 255, 136, 0.22);
    --text: #d7ffe8;
    --muted: #8ccaa7;
    --accent: #00d979;
    --accent-dark: #00a85f;
    --accent-soft: rgba(0, 255, 136, 0.11);
}

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

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    min-width: 320px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    font-family: var(--sans);
    color: var(--text);
    background:
        radial-gradient(circle at top left, rgba(106, 90, 205, 0.16), transparent 30%),
        linear-gradient(160deg, #f6f8fc 0%, #edf2f7 58%, #e9eef7 100%);
}

[data-theme="dark"] body,
body[data-theme="dark"] {
    background:
        radial-gradient(circle at top left, rgba(0, 255, 136, 0.08), transparent 30%),
        linear-gradient(160deg, #030705 0%, #07110d 58%, #020403 100%);
}

a {
    color: inherit;
    text-decoration: none;
}

.container {
    width: min(100% - 2vw, 88rem);
    margin: 0 auto;
}

.site-header {
    position: relative;
    z-index: 10;
    background: color-mix(in srgb, var(--panel-strong) 90%, transparent);
    border-bottom: 1px solid var(--panel-border);
    backdrop-filter: blur(14px);
}

.navbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 14px;
    padding: 10px 0;
    flex-wrap: wrap;
}

.logo {
    color: var(--accent);
    font-weight: 800;
    font-size: 1.25rem;
    white-space: nowrap;
}

.nav-links,
.auth-buttons {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 10px;
}

.nav-links a {
    color: var(--muted);
    font-size: 0.9rem;
    font-weight: 650;
    white-space: nowrap;
}

.nav-links a:hover,
.nav-links a[aria-current="page"] {
    color: var(--accent);
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 34px;
    padding: 7px 14px;
    border: 1px solid var(--panel-border);
    border-radius: 999px;
    color: var(--accent);
    background: var(--panel);
    font-weight: 700;
    font-size: 0.86rem;
}

.btn-primary {
    color: #fff;
    background: linear-gradient(135deg, var(--accent), var(--accent-dark));
    border-color: transparent;
}

[data-theme="dark"] .btn-primary,
body[data-theme="dark"] .btn-primary {
    color: #00140a;
}

.theme-switcher {
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.theme-label {
    color: var(--muted);
    font-size: 0.82rem;
    white-space: nowrap;
}

.switch {
    position: relative;
    display: inline-block;
    width: 44px;
    height: 24px;
}

.switch input {
    width: 0;
    height: 0;
    opacity: 0;
}

.slider {
    position: absolute;
    inset: 0;
    cursor: pointer;
    background: #cfd8ea;
    border-radius: 999px;
    transition: 0.2s ease;
}

.slider::before {
    content: "";
    position: absolute;
    left: 3px;
    top: 3px;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: #fff;
    transition: 0.2s ease;
    box-shadow: 0 2px 8px rgba(31, 42, 68, 0.2);
}

.switch input:checked + .slider {
    background: var(--accent);
}

.switch input:checked + .slider::before {
    transform: translateX(20px);
}

.page {
    flex: 1;
    padding: clamp(24px, 4vw, 46px) 0;
}

.hero-panel,
.content-card,
.topic-card,
.article-body {
    background: var(--panel);
    border: 1px solid var(--panel-border);
    border-radius: var(--radius);
}

.hero-panel {
    padding: clamp(24px, 5vw, 52px);
    margin-bottom: 22px;
}

.hero-kicker,
.eyebrow {
    margin: 0 0 8px;
    color: var(--accent);
    font-size: 0.78rem;
    font-weight: 800;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

h1 {
    margin: 0;
    max-width: 880px;
    font-size: clamp(2rem, 5vw, 4rem);
    line-height: 1.05;
}

.hero-text {
    max-width: 780px;
    margin: 16px 0 0;
    color: var(--muted);
    font-size: clamp(1rem, 2vw, 1.22rem);
    line-height: 1.65;
}

.hero-actions,
.button-row {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 20px;
}

.topic-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
    gap: 14px;
}

.topic-card {
    display: block;
    padding: 18px;
    min-height: 170px;
}

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

.topic-card h2,
.topic-card h3 {
    margin: 0 0 8px;
    font-size: 1.14rem;
    line-height: 1.25;
}

.topic-card p,
.content-card p,
.article-body p,
.article-body li {
    color: var(--muted);
    line-height: 1.7;
}

.topic-card p {
    margin: 0;
}

.lesson-card {
    display: flex;
    flex-direction: column;
}

.lesson-open {
    margin-top: auto;
    padding-top: 14px;
    color: var(--accent);
    font-weight: 800;
    font-size: 0.88rem;
}

.lessons-toolbar {
    max-width: 620px;
    margin-top: 22px;
}

.lessons-search {
    margin-top: 6px;
}

.lessons-status {
    margin-top: 10px;
    font-size: 0.92rem;
}

.lessons-tree {
    display: grid;
    gap: 14px;
}

.lesson-group,
.lesson-child {
    background: var(--panel);
    border: 1px solid var(--panel-border);
    border-radius: var(--radius);
    overflow: hidden;
}

.lesson-child {
    margin: 10px 0 0;
    background: color-mix(in srgb, var(--panel) 84%, var(--accent-soft));
}

.lesson-group summary,
.lesson-child summary {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    padding: 16px 18px;
    cursor: pointer;
    color: var(--text);
    font-weight: 850;
    list-style: none;
}

.lesson-group summary::-webkit-details-marker,
.lesson-child summary::-webkit-details-marker {
    display: none;
}

.lesson-group summary::after,
.lesson-child summary::after {
    content: "+";
    display: grid;
    place-items: center;
    width: 26px;
    height: 26px;
    border-radius: 999px;
    background: var(--accent-soft);
    color: var(--accent);
    font-weight: 900;
}

.lesson-group[open] > summary::after,
.lesson-child[open] > summary::after {
    content: "-";
}

.lesson-list,
.lesson-children {
    display: grid;
    gap: 10px;
    padding: 0 14px 14px;
}

.lesson-row {
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto;
    align-items: center;
    gap: 12px;
    padding: 14px;
    border: 1px solid var(--panel-border);
    border-radius: var(--radius);
    background: var(--panel-strong);
}

.lesson-row h3 {
    margin: 0 0 4px;
    font-size: 1rem;
}

.lesson-row p {
    margin: 0;
    color: var(--muted);
    line-height: 1.5;
    font-size: 0.9rem;
}

.lesson-empty {
    padding: 22px;
    color: var(--muted);
    background: var(--panel);
    border: 1px solid var(--panel-border);
    border-radius: var(--radius);
}

@media (max-width: 640px) {
    .lesson-row {
        grid-template-columns: 1fr;
    }

    .lesson-row .btn {
        width: 100%;
    }
}

.content-grid {
    display: grid;
    grid-template-columns: minmax(0, 1.5fr) minmax(260px, 0.8fr);
    gap: 16px;
    margin-top: 16px;
}

.content-card,
.article-body {
    padding: clamp(20px, 3vw, 32px);
}

.content-card h2,
.article-body h2 {
    margin: 0 0 12px;
    font-size: clamp(1.4rem, 2.4vw, 2rem);
}

.article-body {
    max-width: 900px;
}

.article-body ul {
    padding-left: 20px;
}

.toc {
    display: grid;
    gap: 8px;
    margin-top: 14px;
}

.toc a {
    color: var(--accent);
    font-weight: 700;
}

.kbd-visual {
    display: grid;
    gap: 6px;
    padding: 14px;
    background: var(--bg-accent);
    border-radius: var(--radius);
}

.kbd-row {
    display: grid;
    grid-template-columns: repeat(10, minmax(0, 1fr));
    gap: 5px;
}

.kbd-row span {
    display: grid;
    place-items: center;
    min-height: 34px;
    border-radius: 6px;
    background: var(--panel-strong);
    border: 1px solid var(--panel-border);
    color: var(--text);
    font-weight: 800;
    font-size: 0.9rem;
}

.note {
    border-left: 4px solid var(--accent);
    padding: 12px 14px;
    background: var(--accent-soft);
    color: var(--text);
}

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

@media (max-width: 720px) {
    .navbar,
    .auth-buttons {
        align-items: flex-start;
        flex-direction: column;
    }

    .nav-links {
        width: 100%;
    }

    .site-header {
        position: relative;
        top: auto;
    }

    .topic-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .container {
        width: min(100% - 10px, 88rem);
    }
}