*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    --bg: #fff;
    --text: #1d1d1f;
    --text-secondary: #6e6e73;
    --accent: #0071e3;
    --section-alt: #f5f5f7;
    --font: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'Helvetica Neue', sans-serif;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    -webkit-font-smoothing: antialiased;
}

/* ─── Nav ─────────────────────────────────────────── */

nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 40px;
    height: 52px;
    background: rgba(0, 0, 0, 0.72);
    backdrop-filter: saturate(180%) blur(20px);
    -webkit-backdrop-filter: saturate(180%) blur(20px);
}

.nav-brand {
    font-size: 17px;
    font-weight: 600;
    color: #fff;
    text-decoration: none;
    letter-spacing: -0.01em;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 32px;
}

.nav-links a {
    font-size: 14px;
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    transition: color 0.2s;
}

.nav-links a:hover {
    color: #fff;
}

.nav-links .nav-cta {
    color: var(--accent);
    font-weight: 500;
}

.nav-links .nav-cta:hover {
    color: #409cff;
}

/* ─── Content ──────────────────────────────────────── */

article {
    max-width: 720px;
    margin: 0 auto;
    padding: 140px 40px 80px;
    line-height: 1.7;
}

article h1 {
    font-size: clamp(32px, 5vw, 56px);
    font-weight: 700;
    letter-spacing: -0.025em;
    margin-bottom: 32px;
    line-height: 1.1;
}

article h2 {
    font-size: clamp(24px, 3.5vw, 36px);
    font-weight: 600;
    letter-spacing: -0.02em;
    margin: 48px 0 20px 0;
    line-height: 1.2;
    color: var(--text);
}

article h3 {
    font-size: 20px;
    font-weight: 600;
    margin: 32px 0 12px 0;
    color: var(--text);
}

article p {
    font-size: 18px;
    margin-bottom: 20px;
    color: var(--text);
    line-height: 1.75;
}

article ul,
article ol {
    font-size: 18px;
    margin: 20px 0 20px 24px;
    color: var(--text);
}

article li {
    margin-bottom: 12px;
    line-height: 1.7;
}

article strong {
    font-weight: 600;
    color: var(--text);
}

article em {
    font-style: italic;
    color: var(--text-secondary);
}

article a {
    color: var(--accent);
    text-decoration: none;
    border-bottom: 0.5px solid var(--accent);
    transition: opacity 0.2s;
}

article a:hover {
    opacity: 0.7;
}

article blockquote {
    border-left: 3px solid var(--section-alt);
    padding-left: 24px;
    margin: 32px 0;
    color: var(--text-secondary);
    font-style: italic;
}

article code {
    background: var(--section-alt);
    padding: 2px 6px;
    border-radius: 4px;
    font-family: 'Menlo', 'Monaco', 'Courier New', monospace;
    font-size: 14px;
    color: #c7254e;
}

article pre {
    background: var(--section-alt);
    padding: 16px;
    border-radius: 8px;
    overflow-x: auto;
    margin: 24px 0;
}

article pre code {
    background: none;
    padding: 0;
    color: inherit;
    font-size: 14px;
    line-height: 1.5;
}

/* ─── Footer ───────────────────────────────────────── */

footer {
    border-top: 1px solid #d2d2d7;
    padding: 40px;
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    font-size: 13px;
    color: var(--text-secondary);
}

footer a {
    color: var(--text-secondary);
    text-decoration: none;
}

footer a:hover {
    color: var(--text);
}

.footer-links {
    display: flex;
    gap: 24px;
}

/* ─── Responsive ───────────────────────────────────── */

@media (max-width: 768px) {
    nav {
        padding: 0 20px;
    }

    .nav-links {
        gap: 20px;
    }

    article {
        padding: 120px 24px 60px;
    }

    article h1 {
        margin-bottom: 24px;
    }

    article h2 {
        margin-top: 40px;
        margin-bottom: 16px;
    }

    article p,
    article ul,
    article ol {
        font-size: 16px;
    }

    footer {
        flex-direction: column;
        align-items: flex-start;
        padding: 32px 24px;
    }
}