:root {
    --bg: #12150f;
    --bg-2: #1b2016;
    --panel: #22281c;
    --line: #343c2c;
    --text: #e8eadc;
    --muted: #9aa38a;
    --accent: #d6f26a;
    --accent-ink: #1a2208;
    --danger: #e07a5f;
    --ok: #8fce6a;
    --paper: #f4efe4;
    --paper-ink: #1d1a14;
    --paper-muted: #6b6458;
    --mono: "IBM Plex Mono", ui-monospace, monospace;
    --sans: "Manrope", sans-serif;
    --serif: "Source Serif 4", Georgia, serif;
}

* { box-sizing: border-box; }
html, body { margin: 0; min-height: 100%; }
body {
    font-family: var(--sans);
    background: var(--bg);
    color: var(--text);
    line-height: 1.5;
}
a { color: inherit; text-decoration: none; }
button, input, textarea, select { font: inherit; }

.logo {
    font-weight: 800;
    letter-spacing: -0.04em;
    font-size: 1.15rem;
}
.logo span {
    margin-left: 0.4rem;
    color: var(--accent);
    font-weight: 600;
    font-size: 0.78rem;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.site-header, .site-footer {
    width: min(1120px, calc(100% - 40px));
    margin: 0 auto;
}
.site-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 28px 0;
}
.site-header nav { display: flex; gap: 22px; align-items: center; color: var(--muted); }
.site-footer { color: var(--muted); padding: 40px 0 60px; font-size: 0.92rem; }

.hero {
    width: min(1120px, calc(100% - 40px));
    margin: 20px auto 70px;
    display: grid;
    grid-template-columns: 1.2fr 0.8fr;
    gap: 48px;
    align-items: center;
}
.kicker {
    color: var(--accent);
    font-family: var(--mono);
    font-size: 0.8rem;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}
.hero h1 {
    font-size: clamp(2.4rem, 5vw, 4.2rem);
    line-height: 0.95;
    letter-spacing: -0.05em;
    margin: 12px 0 18px;
}
.lead { color: var(--muted); font-size: 1.12rem; max-width: 46ch; }
.hero-card {
    background: var(--bg-2);
    border: 1px solid var(--line);
    padding: 28px;
}
.hero-card h3 { margin: 0 0 14px; }
.hero-card ol { margin: 0; padding-left: 18px; color: var(--muted); }
.hero-card li + li { margin-top: 10px; }

.features, .track-grid {
    width: min(1120px, calc(100% - 40px));
    margin: 0 auto 70px;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 16px;
}
.card, .feature, .track {
    background: var(--bg-2);
    border: 1px solid var(--line);
    padding: 22px;
}
.feature h3, .track h3 { margin: 8px 0; }
.muted, .feature p, .track p { color: var(--muted); }
.lang-tag {
    display: inline-block;
    font-family: var(--mono);
    font-size: 0.75rem;
    color: var(--accent);
    border: 1px solid var(--line);
    padding: 3px 8px;
}

.btn, button.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background: var(--accent);
    color: var(--accent-ink);
    border: 0;
    padding: 11px 16px;
    font-weight: 700;
    cursor: pointer;
}
.btn-small { padding: 8px 12px; font-size: 0.92rem; }
.btn-ghost {
    background: transparent;
    color: var(--text);
    border: 1px solid var(--line);
}
.btn-danger { background: var(--danger); color: #fff; }
.btn-row { display: flex; gap: 10px; flex-wrap: wrap; }

.auth-wrap {
    width: min(440px, calc(100% - 40px));
    margin: 60px auto;
    background: var(--bg-2);
    border: 1px solid var(--line);
    padding: 32px;
}
.auth-wrap h1 { margin: 8px 0 22px; letter-spacing: -0.04em; }
label { display: block; margin: 0 0 6px; font-size: 0.88rem; color: var(--muted); }
input, textarea, select {
    width: 100%;
    background: var(--bg);
    color: var(--text);
    border: 1px solid var(--line);
    padding: 11px 12px;
    margin-bottom: 14px;
}
textarea { min-height: 140px; resize: vertical; }
.form-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }

.app-shell { display: grid; grid-template-columns: 250px 1fr; min-height: 100vh; }
.sidebar {
    background: var(--bg-2);
    border-right: 1px solid var(--line);
    padding: 24px 18px;
    display: flex;
    flex-direction: column;
    position: sticky;
    top: 0;
    height: 100vh;
}
.sidebar-user { margin: 28px 0 18px; }
.sidebar-user span, .nav-label { color: var(--muted); font-size: 0.82rem; }
.side-nav { display: flex; flex-direction: column; gap: 4px; }
.side-nav a, .sidebar-out {
    padding: 9px 10px;
    color: var(--muted);
}
.side-nav a.active, .side-nav a:hover { background: var(--panel); color: var(--text); }
.nav-label { margin: 20px 10px 8px; text-transform: uppercase; letter-spacing: 0.08em; }
.sidebar-out { margin-top: auto; }

.app-main { padding: 32px 40px 60px; }
.page-head { display: flex; justify-content: space-between; gap: 16px; align-items: flex-end; margin-bottom: 24px; }
.page-head h1 { margin: 0; letter-spacing: -0.04em; font-size: 1.9rem; }

.stat-grid, .course-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 14px;
    margin-bottom: 28px;
}
.stat, .course-card {
    background: var(--bg-2);
    border: 1px solid var(--line);
    padding: 18px;
}
.stat b { display: block; font-size: 1.8rem; letter-spacing: -0.04em; }
.course-card h3 { margin: 10px 0 8px; }
.progress {
    height: 6px;
    background: var(--panel);
    margin: 12px 0;
}
.progress > i {
    display: block;
    height: 100%;
    background: var(--accent);
}
.meta { color: var(--muted); font-size: 0.88rem; }

.table-wrap { overflow: auto; border: 1px solid var(--line); }
table { width: 100%; border-collapse: collapse; background: var(--bg-2); }
th, td { text-align: left; padding: 12px 14px; border-bottom: 1px solid var(--line); vertical-align: top; }
th { color: var(--muted); font-size: 0.8rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.05em; }
.badge {
    display: inline-block;
    font-size: 0.75rem;
    padding: 3px 7px;
    border: 1px solid var(--line);
    color: var(--muted);
}
.badge-ok { color: var(--ok); }
.badge-warn { color: #e6c36a; }
.badge-acc { color: var(--accent-ink); background: var(--accent); border-color: var(--accent); }

.flash { padding: 12px 14px; margin-bottom: 18px; border: 1px solid var(--line); }
.flash-ok { color: var(--ok); }
.flash-error { color: var(--danger); }

.lesson-layout {
    display: grid;
    grid-template-columns: 280px 1fr;
    gap: 24px;
}
.lesson-nav {
    background: var(--bg-2);
    border: 1px solid var(--line);
    padding: 16px;
    position: sticky;
    top: 16px;
    max-height: calc(100vh - 32px);
    overflow: auto;
}
.lesson-nav h4 { margin: 16px 0 8px; font-size: 0.82rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.06em; }
.lesson-nav h4:first-child { margin-top: 0; }
.lesson-nav a { display: block; padding: 7px 8px; color: var(--muted); font-size: 0.92rem; }
.lesson-nav a.active { color: var(--accent-ink); background: var(--accent); }
.lesson-nav a.done { color: var(--text); }

.lesson-paper {
    background: var(--paper);
    color: var(--paper-ink);
    padding: 36px 40px 48px;
    min-height: 70vh;
}
.lesson-paper h1, .lesson-paper h2, .lesson-paper h3 { font-family: var(--serif); letter-spacing: -0.03em; }
.lesson-paper h1 { margin-top: 0; }
.lesson-body { font-family: var(--serif); font-size: 1.12rem; line-height: 1.7; }
.lesson-body h2 { margin-top: 1.6em; }
.lesson-body p { margin: 0 0 1em; }
.lesson-body ul, .lesson-body ol { margin: 0 0 1em; padding-left: 1.2em; }
.lesson-body pre, .code-block {
    font-family: var(--mono);
    font-size: 0.88rem;
    background: #1b1f16;
    color: #e7edcf;
    padding: 14px 16px;
    overflow: auto;
    line-height: 1.55;
}
.lesson-body code, .inline-code {
    font-family: var(--mono);
    font-size: 0.88em;
    background: #e7e0d2;
    padding: 0 4px;
}
.lesson-body pre code { background: none; padding: 0; color: inherit; }
.callout {
    border-left: 4px solid #b7c04a;
    background: #efe8d6;
    padding: 12px 14px;
    margin: 0 0 1em;
}
.lesson-actions {
    display: flex;
    justify-content: space-between;
    gap: 12px;
    margin-top: 28px;
    padding-top: 18px;
    border-top: 1px solid #ddd4c2;
}

.quiz-item { margin-bottom: 22px; }
.quiz-item label.opt {
    display: block;
    border: 1px solid #ddd4c2;
    padding: 10px 12px;
    margin-bottom: 8px;
    cursor: pointer;
    background: #fffdf8;
}
.practice-editor textarea {
    min-height: 260px;
    font-family: var(--mono);
    background: #1b1f16;
    color: #e7edcf;
    border-color: #2a3120;
}

.announce { border-left: 3px solid var(--accent); padding-left: 14px; margin-bottom: 18px; }
.split { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }

@media (max-width: 900px) {
    .hero, .features, .track-grid, .stat-grid, .course-grid, .lesson-layout, .form-grid, .split, .app-shell {
        grid-template-columns: 1fr;
    }
    .sidebar { position: relative; height: auto; }
    .app-main { padding: 22px 16px 40px; }
    .lesson-paper { padding: 22px 18px 32px; }
}