/* ---------------------------------------------------------------
   Yu-Fang Yang - personal site
   Typography: Cormorant Garamond (serif headings), Inter (body)
   Theme: warm off-white + deep charcoal
   --------------------------------------------------------------- */

:root {
    --bg: #faf9f5;
    --bg-card: #ffffff;
    --bg-dark: #14181d;
    --ink: #1a1a1a;
    --ink-soft: #4a4a4a;
    --ink-mute: #7a7a7a;
    --ink-inv: #ecebe4;
    --ink-inv-soft: #b8b7ae;
    --rule: #e6e3da;
    --rule-dark: #2b2f35;
    --accent: #6b5c3f;
    --maxw: 960px;
    --nav-h: 72px;
}

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

html { scroll-behavior: smooth; }

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    font-weight: 300;
    font-size: 17px;
    line-height: 1.65;
    color: var(--ink);
    background: var(--bg);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

h1, h2, h3, h4 {
    font-family: 'Cormorant Garamond', Georgia, serif;
    font-weight: 500;
    letter-spacing: -0.01em;
    line-height: 1.15;
    color: var(--ink);
}

a { color: var(--ink); text-decoration: none; border-bottom: 1px solid transparent; transition: border-color 180ms ease, color 180ms ease; }
a:hover { border-bottom-color: var(--ink); }

p { margin-bottom: 1rem; }

/* ---------- Skip nav ---------- */
.skip-nav {
    position: absolute; left: -9999px; top: 0;
    background: var(--ink); color: var(--bg); padding: 0.6rem 1rem;
    z-index: 1000; font-size: 14px;
}
.skip-nav:focus { left: 1rem; top: 1rem; }

/* ---------- Nav ---------- */
#navbar {
    position: sticky; top: 0; z-index: 100;
    display: flex; align-items: center; justify-content: space-between;
    padding: 0 2rem;
    height: var(--nav-h);
    background: rgba(250, 249, 245, 0.85);
    backdrop-filter: saturate(140%) blur(10px);
    -webkit-backdrop-filter: saturate(140%) blur(10px);
    border-bottom: 1px solid transparent;
    transition: border-color 200ms ease, background 200ms ease;
}
#navbar.scrolled { border-bottom-color: var(--rule); }

.nav-logo {
    font-family: 'Cormorant Garamond', Georgia, serif;
    font-size: 1.4rem;
    font-weight: 500;
    letter-spacing: 0.01em;
    border-bottom: none;
}
.nav-logo:hover { border-bottom: none; color: var(--accent); }

.nav-links { display: flex; gap: 2rem; }
.nav-links a {
    font-size: 0.92rem;
    font-weight: 400;
    color: var(--ink-soft);
    border-bottom: none;
    padding-bottom: 2px;
}
.nav-links a:hover { color: var(--ink); border-bottom: 1px solid var(--ink); }
.nav-links a.active { color: var(--ink); border-bottom: 1px solid var(--ink); }

/* mobile nav toggle */
.nav-toggle {
    display: none;
    width: 32px; height: 32px;
    background: transparent; border: none; cursor: pointer;
    flex-direction: column; justify-content: center; align-items: center;
    gap: 5px;
}
.nav-toggle span {
    display: block; width: 22px; height: 1.5px; background: var(--ink);
    transition: transform 200ms ease, opacity 200ms ease;
}

/* ---------- Layout sections ---------- */
main { min-height: calc(100vh - var(--nav-h)); }

.section-light, .section-dark {
    padding: 6rem 2rem;
}
.section-light { background: var(--bg); color: var(--ink); }
.section-dark { background: var(--bg-dark); color: var(--ink-inv); }

.section-light > *, .section-dark > * { max-width: var(--maxw); margin-left: auto; margin-right: auto; }

.section-heading {
    font-size: 2.2rem;
    font-weight: 500;
    margin-bottom: 2.5rem;
    letter-spacing: -0.015em;
}
.section-label {
    font-family: 'Inter', sans-serif;
    font-size: 0.78rem;
    font-weight: 400;
    letter-spacing: 0.18em;
    text-transform: uppercase;
    color: var(--ink-inv-soft);
    margin-bottom: 2rem;
}

/* ---------- Hero ---------- */
.hero-plain {
    padding-top: 8rem;
    padding-bottom: 6rem;
}
.hero-plain-content { max-width: 760px; }
.hero-name {
    font-size: clamp(2.8rem, 6vw, 4.2rem);
    font-weight: 400;
    margin-bottom: 1.2rem;
    letter-spacing: -0.02em;
}
.hero-role {
    font-size: 1.05rem;
    color: var(--ink-soft);
    margin-bottom: 0.6rem;
    font-weight: 400;
}
.hero-lede {
    font-size: 1.25rem;
    color: var(--ink-soft);
    line-height: 1.55;
    margin-bottom: 2.5rem;
    max-width: 620px;
    font-weight: 300;
}
.hero-buttons { display: flex; flex-wrap: wrap; gap: 0.9rem; }

/* ---------- Buttons ---------- */
.btn {
    display: inline-block;
    padding: 0.7rem 1.3rem;
    font-size: 0.92rem;
    font-weight: 400;
    letter-spacing: 0.01em;
    border-radius: 2px;
    cursor: pointer;
    transition: background 180ms ease, color 180ms ease, border-color 180ms ease;
    border-bottom: none;
}
.btn-bordered {
    background: transparent;
    color: var(--ink);
    border: 1px solid var(--ink);
}
.btn-bordered:hover { background: var(--ink); color: var(--bg); border-bottom: 1px solid var(--ink); }

/* ---------- Recent work ---------- */
.recent-work { padding-top: 2rem; }
.work-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.8rem;
}
.work-card {
    padding: 1.8rem;
    background: var(--bg-card);
    border: 1px solid var(--rule);
    border-radius: 3px;
    transition: transform 220ms ease, box-shadow 220ms ease;
}
.work-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 14px 32px -18px rgba(0,0,0,0.15);
}
.card-title {
    font-size: 1.35rem;
    margin-bottom: 0.8rem;
    line-height: 1.25;
    font-weight: 500;
}
.card-description {
    font-size: 0.96rem;
    color: var(--ink-soft);
    margin-bottom: 0.9rem;
    line-height: 1.55;
}
.card-meta {
    font-size: 0.82rem;
    color: var(--ink-mute);
    letter-spacing: 0.04em;
    text-transform: uppercase;
    margin-bottom: 0;
}

/* ---------- Connect (dark) ---------- */
.connect { text-align: left; }
.connect .section-label { color: var(--ink-inv-soft); }
.social-row {
    display: flex; flex-wrap: wrap; gap: 2rem;
}
.social-link {
    color: var(--ink-inv);
    font-size: 1.1rem;
    font-family: 'Cormorant Garamond', Georgia, serif;
    font-weight: 400;
    letter-spacing: 0.01em;
    border-bottom: 1px solid transparent;
}
.social-link:hover { border-bottom: 1px solid var(--ink-inv); color: var(--ink-inv); }

/* ---------- Generic article / page content ---------- */
.page-content {
    max-width: var(--maxw);
    margin: 0 auto;
    padding: 4rem 2rem 6rem;
}
.page-content h1 {
    font-size: clamp(2.2rem, 5vw, 3rem);
    font-weight: 500;
    margin-bottom: 0.8rem;
    letter-spacing: -0.015em;
}
.page-content .page-lede {
    font-size: 1.15rem;
    color: var(--ink-soft);
    margin-bottom: 3rem;
    max-width: 640px;
    font-weight: 300;
}
.page-content h2 {
    font-size: 1.7rem;
    font-weight: 500;
    margin-top: 3rem;
    margin-bottom: 1rem;
}
.page-content h3 {
    font-size: 1.25rem;
    font-family: 'Inter', sans-serif;
    font-weight: 400;
    margin-top: 1.8rem;
    margin-bottom: 0.4rem;
    letter-spacing: 0;
}
.page-content p { margin-bottom: 1rem; color: var(--ink-soft); max-width: 720px; }
.page-content ul, .page-content ol { margin: 0 0 1.2rem 1.4rem; color: var(--ink-soft); }
.page-content li { margin-bottom: 0.4rem; }
.page-content hr { border: none; border-top: 1px solid var(--rule); margin: 3rem 0; }

/* publication list */
.pub-list { list-style: none; margin-left: 0; }
.pub-list li {
    padding: 1.2rem 0;
    border-bottom: 1px solid var(--rule);
    margin-bottom: 0;
}
.pub-list li:last-child { border-bottom: none; }
.pub-title { font-weight: 400; color: var(--ink); display: block; margin-bottom: 0.3rem; }
.pub-meta { font-size: 0.88rem; color: var(--ink-mute); letter-spacing: 0.02em; }
.pub-authors { font-size: 0.92rem; color: var(--ink-soft); margin-bottom: 0.2rem; }

/* ---------- Footer ---------- */
footer {
    background: var(--bg);
    padding: 3rem 2rem 2.5rem;
    border-top: 1px solid var(--rule);
    color: var(--ink-soft);
    font-size: 0.9rem;
}
footer > * { max-width: var(--maxw); margin-left: auto; margin-right: auto; }
.footer-nav {
    display: flex; flex-wrap: wrap; gap: 1.8rem;
    margin-bottom: 1.8rem;
    padding-bottom: 1.8rem;
    border-bottom: 1px solid var(--rule);
}
.footer-nav a { color: var(--ink-soft); font-size: 0.9rem; border-bottom: none; }
.footer-nav a:hover { color: var(--ink); }
.footer-right { display: flex; gap: 1.2rem; }
.footer-right a { color: var(--ink-soft); border-bottom: none; }
.footer-right a:hover { color: var(--ink); }

.back-to-top {
    display: inline-block;
    margin-top: 1.5rem;
    font-size: 0.85rem;
    color: var(--ink-mute);
    border-bottom: none;
}
.back-to-top:hover { color: var(--ink); }

/* ---------- Fade-in animation ---------- */
.fade-in {
    opacity: 0;
    transform: translateY(18px);
    transition: opacity 700ms ease, transform 700ms ease;
}
.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ---------- Responsive ---------- */
@media (max-width: 720px) {
    #navbar { padding: 0 1.2rem; }
    .nav-toggle { display: flex; }
    .nav-links {
        position: absolute; top: var(--nav-h); left: 0; right: 0;
        flex-direction: column; gap: 0;
        background: var(--bg);
        border-bottom: 1px solid var(--rule);
        padding: 0.6rem 1.2rem;
        display: none;
    }
    .nav-links.open { display: flex; }
    .nav-links a { padding: 0.9rem 0; border-bottom: 1px solid var(--rule); }
    .nav-links a:last-child { border-bottom: none; }

    .section-light, .section-dark { padding: 4rem 1.2rem; }
    .hero-plain { padding-top: 4rem; padding-bottom: 3rem; }
    .page-content { padding: 2.5rem 1.2rem 4rem; }
    .section-heading { font-size: 1.8rem; margin-bottom: 1.8rem; }
    .work-grid { gap: 1.2rem; }
    .hero-buttons { gap: 0.6rem; }
    .btn { padding: 0.6rem 1rem; font-size: 0.88rem; }
    footer { padding: 2rem 1.2rem 1.8rem; }
}