:root {
    --bg: #0e1116;
    --bg-elev: #161b22;
    --bg-elev-2: #1f262f;
    --border: #2a313c;
    --text: #e6edf3;
    --text-muted: #9da7b3;
    --accent: #3fb950;
    --accent-soft: rgba(63, 185, 80, 0.15);
    --danger: #f85149;
    --warning: #d29922;
    --info: #58a6ff;
    --radius: 10px;
}

* { box-sizing: border-box; }

html, body {
    margin: 0;
    padding: 0;
    background: var(--bg);
    color: var(--text);
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Inter",
                 Roboto, "Helvetica Neue", Arial, sans-serif;
    font-size: 16px;
    line-height: 1.55;
}

a { color: var(--info); text-decoration: none; }
a:hover { text-decoration: underline; }

code {
    font-family: ui-monospace, "SF Mono", "JetBrains Mono",
                 Menlo, Consolas, monospace;
    background: var(--bg-elev-2);
    padding: 1px 6px;
    border-radius: 4px;
    font-size: 0.92em;
}

.container {
    max-width: 960px;
    margin: 0 auto;
    padding: 0 20px;
}

.site-header {
    background: linear-gradient(180deg, #12181f 0%, #0e1116 100%);
    border-bottom: 1px solid var(--border);
    padding: 48px 0 36px;
}
.site-header h1 {
    margin: 0 0 6px;
    font-size: 2.2rem;
    letter-spacing: -0.01em;
}
.tagline {
    margin: 0;
    color: var(--text-muted);
}

main { padding: 36px 0 60px; }

.notice {
    background: linear-gradient(180deg, rgba(210, 153, 34, 0.18) 0%, rgba(210, 153, 34, 0.06) 100%);
    border: 1px solid var(--warning);
    border-left: 4px solid var(--warning);
    border-radius: var(--radius);
    padding: 18px 22px;
    margin-bottom: 32px;
}
.notice__title {
    margin: 0 0 8px;
    font-size: 1.1rem;
    color: var(--warning);
    letter-spacing: 0.01em;
}
.notice p { margin: 6px 0; }
.notice__link {
    font-family: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;
    color: var(--warning);
    font-weight: 600;
}
.notice__link:hover { color: #f3c96b; }
.notice__hint {
    color: var(--text-muted);
    font-size: 0.92rem;
}

.intro h2,
.labs h2,
.lab-nav__title {
    margin-top: 0;
    font-size: 1.3rem;
    border-bottom: 1px solid var(--border);
    padding-bottom: 8px;
}

.lab-nav {
    background: var(--bg-elev);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 18px 22px;
    margin-bottom: 32px;
}
.lab-nav__title {
    margin: 0 0 12px;
}
.lab-nav__list {
    list-style: none;
    margin: 0;
    padding: 0;
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 8px;
}
.lab-nav__list a {
    display: flex;
    flex-direction: column;
    gap: 2px;
    padding: 10px 12px;
    background: var(--bg-elev-2);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text);
    transition: border-color 0.15s ease, color 0.15s ease;
}
.lab-nav__list a:hover {
    border-color: var(--info);
    color: var(--info);
    text-decoration: none;
}
.lab-nav__name {
    font-weight: 600;
}
.lab-nav__path {
    font-family: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;
    font-size: 0.85rem;
    color: var(--text-muted);
}

.labs { margin-top: 40px; }

.lab-card {
    background: var(--bg-elev);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 20px 22px;
    margin-bottom: 18px;
    transition: border-color 0.15s ease, transform 0.15s ease;
}
.lab-card:hover {
    border-color: var(--info);
}
.lab-card__header {
    display: flex;
    gap: 8px;
    margin-bottom: 8px;
}
.lab-card__tag,
.lab-card__difficulty {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    padding: 2px 8px;
    border-radius: 999px;
    background: var(--bg-elev-2);
    color: var(--text-muted);
    border: 1px solid var(--border);
}
.lab-card__difficulty[data-level="easy"]    { color: var(--accent);  border-color: var(--accent); }
.lab-card__difficulty[data-level="medium"]  { color: var(--warning); border-color: var(--warning); }
.lab-card__difficulty[data-level="hard"]    { color: var(--danger);  border-color: var(--danger); }

.lab-card h3 {
    margin: 6px 0 10px;
    font-size: 1.2rem;
}
.lab-card h3 a { color: var(--text); }
.lab-card h3 a:hover { color: var(--info); text-decoration: none; }

.lab-card__goal {
    background: var(--accent-soft);
    border-left: 3px solid var(--accent);
    padding: 10px 12px;
    border-radius: 6px;
    margin: 12px 0;
}

.btn {
    display: inline-block;
    background: var(--info);
    color: #0e1116;
    padding: 8px 14px;
    border-radius: 6px;
    font-weight: 600;
    font-size: 0.92rem;
}
.btn:hover { background: #79b8ff; text-decoration: none; }

.site-footer {
    border-top: 1px solid var(--border);
    padding: 20px 0;
    color: var(--text-muted);
    font-size: 0.9rem;
}