:root {
            --bg: #f6f7fb;
            --surface: #ffffff;
            --text: #1f2430;
            --muted: #5b6475;
            --accent: #4f46e5;
            --accent-soft: #eef0ff;
            --border: #e3e6ef;
        }

        @media (prefers-color-scheme: dark) {
            :root {
                --bg: #12141a;
                --surface: #1b1e27;
                --text: #eef0f6;
                --muted: #a3abbd;
                --accent: #8b87ff;
                --accent-soft: #272a3d;
                --border: #2b3040;
            }
        }

        * { box-sizing: border-box; }

        body {
            margin: 0;
            font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
            background: var(--bg);
            color: var(--text);
        }

        header {
            padding: 2rem 1.5rem 1rem;
            max-width: 1100px;
            margin: 0 auto;
        }

        header h1 {
            margin: 0;
            font-size: clamp(1.5rem, 4vw, 2.2rem);
        }

        /* ---------- NAV ---------- */
        nav {
            position: sticky;
            top: 0;
            z-index: 10;
            display: flex;
            flex-wrap: wrap;
            gap: 0.5rem;
            max-width: 1100px;
            margin: 0.5rem auto 1.5rem;
            padding: 0.6rem;
            background: var(--surface);
            border: 1px solid var(--border);
            border-radius: 14px;
            box-shadow: 0 4px 14px rgba(0, 0, 0, 0.06);
        }

        nav a {
            padding: 0.55rem 1.1rem;
            border-radius: 999px;
            color: var(--muted);
            font-weight: 500;
            font-size: 0.95rem;
            text-decoration: none;
            transition: background 0.2s, color 0.2s, transform 0.2s;
        }

        nav a:hover {
            background: var(--accent-soft);
            color: var(--accent);
            transform: translateY(-1px);
        }

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

        nav a.active,
        nav a[aria-current="page"] {
            background: var(--accent);
            color: #fff;
        }

        @media (max-width: 480px) {
            nav a { flex: 1 1 calc(50% - 0.5rem); text-align: center; }
        }