/* ============================================================
   Lanyin (Elaine) Zhang — personal site
   Design language: "engineering paper" — warm paper ground,
   ink typography, serif display + mono labels, one warm accent.
   ============================================================ */

:root {
    --paper: #faf7f1;
    --paper-soft: #f3efe5;
    --ink: #1d1b16;
    --ink-soft: #6b675c;
    --ink-faint: #98927f;
    --line: #e3ddcf;
    --line-strong: #cfc7b4;
    --accent: #c04a17;
    --accent-soft: #c04a1722;

    --font-display: "Newsreader", "Noto Serif SC", "Songti SC", serif;
    --font-body: "Inter", "Noto Sans SC", "PingFang SC", -apple-system, sans-serif;
    --font-mono: "IBM Plex Mono", "SFMono-Regular", Menlo, monospace;

    --frame-w: 1080px;
    --pad: clamp(1.25rem, 4vw, 3rem);
}

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

html { scroll-behavior: smooth; }

body {
    font-family: var(--font-body);
    background: var(--paper);
    color: var(--ink);
    line-height: 1.7;
    font-size: 1rem;
    -webkit-font-smoothing: antialiased;
    text-rendering: optimizeLegibility;
}

::selection { background: var(--accent); color: var(--paper); }

a { color: inherit; }

[hidden] { display: none !important; }

/* ---------- the paper frame: hairline rails down the page ---------- */

.frame {
    max-width: var(--frame-w);
    margin: 0 auto;
    border-left: 1px solid var(--line);
    border-right: 1px solid var(--line);
    min-height: 100vh;
    background:
        radial-gradient(var(--line) 0.5px, transparent 0.5px) 0 0 / 28px 28px,
        var(--paper);
    background-attachment: fixed;
}

@media (max-width: 1120px) {
    .frame { border-left: none; border-right: none; }
}

/* ---------- nav ---------- */

.nav {
    position: sticky;
    top: 0;
    z-index: 100;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    padding: 0.9rem var(--pad);
    border-bottom: 1px solid var(--line);
    background: color-mix(in srgb, var(--paper) 88%, transparent);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
}

.nav-name {
    font-family: var(--font-display);
    font-size: 1.15rem;
    font-weight: 600;
    letter-spacing: -0.01em;
    text-decoration: none;
    white-space: nowrap;
}

.nav-name em { color: var(--accent); font-style: normal; }

.nav-links {
    display: flex;
    gap: clamp(0.8rem, 2.5vw, 1.8rem);
    align-items: center;
}

.nav-links a {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    text-decoration: none;
    color: var(--ink-soft);
    transition: color 0.2s ease;
}

.nav-links a:hover { color: var(--accent); }

@media (max-width: 720px) {
    .nav-links a:not(.nav-link-keep) { display: none; }
}

/* language toggle — always visible, deliberately prominent */

.lang-toggle {
    display: inline-flex;
    border: 1px solid var(--line-strong);
    border-radius: 999px;
    overflow: hidden;
    background: var(--paper);
    cursor: pointer;
    padding: 0;
    flex-shrink: 0;
}

.lang-toggle span {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    letter-spacing: 0.08em;
    padding: 0.35rem 0.8rem;
    color: var(--ink-soft);
    transition: background 0.25s ease, color 0.25s ease;
}

.lang-toggle span.lang-active {
    background: var(--ink);
    color: var(--paper);
}

.lang-toggle:hover span:not(.lang-active) { color: var(--accent); }

/* ---------- shared section scaffolding ---------- */

.section {
    padding: clamp(4rem, 9vw, 7rem) var(--pad);
    border-bottom: 1px solid var(--line);
}

.section-head {
    display: flex;
    align-items: baseline;
    gap: 1.25rem;
    margin-bottom: clamp(2rem, 5vw, 3.5rem);
}

.section-num {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    letter-spacing: 0.14em;
    color: var(--accent);
}

.section-head h2 {
    font-family: var(--font-display);
    font-size: clamp(1.9rem, 4vw, 2.8rem);
    font-weight: 500;
    letter-spacing: -0.02em;
    line-height: 1.1;
}

.section-rule {
    flex: 1;
    height: 1px;
    background: var(--line-strong);
    transform-origin: left center;
}

.eyebrow {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    letter-spacing: 0.16em;
    text-transform: uppercase;
    color: var(--ink-faint);
}

/* ---------- hero ---------- */

.hero {
    position: relative;
    padding: clamp(5rem, 12vw, 9rem) var(--pad) clamp(4rem, 9vw, 7rem);
    border-bottom: 1px solid var(--line);
    overflow: hidden;
}

#hero-canvas {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
}

.hero-inner { position: relative; }

.hero .eyebrow {
    display: block;
    margin-bottom: 2rem;
    color: var(--accent);
}

.hero h1 {
    font-family: var(--font-display);
    font-weight: 500;
    font-size: clamp(2.4rem, 6.5vw, 4.6rem);
    line-height: 1.08;
    letter-spacing: -0.025em;
    max-width: 18ch;
}

.hero h1 .accent { color: var(--accent); font-style: italic; }

.hero-line-mask { display: block; overflow: hidden; }
.hero-line { display: block; }

.hero-sub {
    margin-top: 2.2rem;
    max-width: 56ch;
    color: var(--ink-soft);
    font-size: clamp(1rem, 1.6vw, 1.12rem);
}

.hero-cta {
    margin-top: 2.6rem;
    display: flex;
    gap: 1.5rem;
    flex-wrap: wrap;
    align-items: center;
}

.btn {
    font-family: var(--font-mono);
    font-size: 0.78rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    text-decoration: none;
    padding: 0.7rem 1.4rem;
    border: 1px solid var(--ink);
    border-radius: 999px;
    transition: background 0.25s ease, color 0.25s ease, border-color 0.25s ease;
}

.btn-solid { background: var(--ink); color: var(--paper); }
.btn-solid:hover { background: var(--accent); border-color: var(--accent); }
.btn-ghost { color: var(--ink); }
.btn-ghost:hover { border-color: var(--accent); color: var(--accent); }

/* ---------- about ---------- */

.about-grid {
    display: grid;
    grid-template-columns: minmax(0, 1.6fr) minmax(0, 1fr);
    gap: clamp(2rem, 5vw, 4.5rem);
    align-items: start;
}

.about-text p {
    font-size: clamp(1.05rem, 1.7vw, 1.2rem);
    line-height: 1.85;
    color: var(--ink);
}

.about-text p + p { margin-top: 1.4rem; }

.about-text .lede {
    font-family: var(--font-display);
    font-size: clamp(1.3rem, 2.4vw, 1.65rem);
    line-height: 1.5;
}

.about-aside { display: grid; gap: 1.5rem; }

.about-photo {
    width: 100%;
    max-width: 320px;
    aspect-ratio: 4 / 5;
    object-fit: cover;
    border: 1px solid var(--line-strong);
    filter: saturate(0.85) contrast(1.02);
}

.about-facts {
    list-style: none;
    border-top: 1px solid var(--line-strong);
}

.about-facts li {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    padding: 0.7rem 0;
    border-bottom: 1px solid var(--line);
    font-size: 0.9rem;
}

.about-facts .k {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--ink-faint);
    padding-top: 0.2rem;
    white-space: nowrap;
}

.about-facts .v { text-align: right; color: var(--ink-soft); }

@media (max-width: 820px) {
    .about-grid { grid-template-columns: 1fr; }
    .about-photo { max-width: 260px; }
}

/* ---------- directions (research map) ---------- */

.directions-intro {
    max-width: 62ch;
    color: var(--ink-soft);
    margin-bottom: clamp(2rem, 4vw, 3rem);
}

.directions-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    border-top: 1px solid var(--line-strong);
    border-left: 1px solid var(--line-strong);
}

.direction {
    border-right: 1px solid var(--line-strong);
    border-bottom: 1px solid var(--line-strong);
    padding: clamp(1.5rem, 3vw, 2.5rem);
    position: relative;
    transition: background 0.3s ease;
}

.direction:hover { background: var(--paper-soft); }

.direction-index {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    letter-spacing: 0.14em;
    color: var(--accent);
}

.direction h3 {
    font-family: var(--font-display);
    font-size: clamp(1.3rem, 2.2vw, 1.6rem);
    font-weight: 500;
    letter-spacing: -0.01em;
    margin: 0.8rem 0 1rem;
    line-height: 1.25;
}

.direction p { color: var(--ink-soft); font-size: 0.95rem; }

.direction ul {
    margin-top: 1.1rem;
    list-style: none;
}

.direction li {
    position: relative;
    padding-left: 1.1rem;
    color: var(--ink-soft);
    font-size: 0.9rem;
    line-height: 1.6;
    margin-top: 0.45rem;
}

.direction li::before {
    content: "";
    position: absolute;
    left: 0;
    top: 0.62em;
    width: 5px;
    height: 5px;
    background: var(--accent);
    border-radius: 50%;
}

@media (max-width: 820px) {
    .directions-grid { grid-template-columns: 1fr; }
}

/* ---------- projects ---------- */

.project-featured {
    border: 1px solid var(--line-strong);
    padding: clamp(1.6rem, 3.5vw, 2.8rem);
    margin-bottom: 2rem;
    background: var(--paper-soft);
    position: relative;
    overflow: hidden;
}

.project-featured::after {
    content: "ERC-7527";
    position: absolute;
    right: -0.4rem;
    bottom: -1.8rem;
    font-family: var(--font-display);
    font-size: clamp(4rem, 10vw, 7rem);
    font-style: italic;
    color: var(--accent);
    opacity: 0.08;
    pointer-events: none;
    white-space: nowrap;
}

.project-featured h3 {
    font-family: var(--font-display);
    font-size: clamp(1.6rem, 3vw, 2.2rem);
    font-weight: 500;
    letter-spacing: -0.015em;
    margin: 0.8rem 0 1rem;
    line-height: 1.2;
}

.project-featured p {
    color: var(--ink-soft);
    max-width: 60ch;
    margin-bottom: 1.6rem;
}

.project-links { display: flex; gap: 1.25rem; flex-wrap: wrap; }

.text-link {
    font-family: var(--font-mono);
    font-size: 0.76rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    text-decoration: none;
    color: var(--ink);
    border-bottom: 1px solid var(--line-strong);
    padding-bottom: 0.2rem;
    transition: color 0.2s ease, border-color 0.2s ease;
}

.text-link:hover { color: var(--accent); border-color: var(--accent); }

.text-link .arrow { color: var(--accent); }

.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(min(100%, 300px), 1fr));
    gap: 1.25rem;
}

.project-card {
    border: 1px solid var(--line-strong);
    padding: 1.6rem;
    display: flex;
    flex-direction: column;
    gap: 0.7rem;
    text-decoration: none;
    transition: background 0.3s ease, transform 0.3s ease;
}

.project-card:hover { background: var(--paper-soft); transform: translateY(-3px); }

.project-tag {
    font-family: var(--font-mono);
    font-size: 0.66rem;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--accent);
}

.project-card h3 {
    font-family: var(--font-display);
    font-size: 1.3rem;
    font-weight: 500;
    line-height: 1.25;
}

.project-card p { color: var(--ink-soft); font-size: 0.92rem; flex: 1; }

.project-card .text-link { align-self: flex-start; }

/* ---------- writings ---------- */

.writings-list { list-style: none; border-top: 1px solid var(--line-strong); }

.writings-item {
    border-bottom: 1px solid var(--line);
}

.writings-item a {
    display: grid;
    grid-template-columns: 7.5rem 1fr auto;
    gap: 1.5rem;
    align-items: baseline;
    padding: 1.3rem 0.5rem;
    text-decoration: none;
    transition: background 0.25s ease;
}

.writings-item a:hover { background: var(--paper-soft); }
.writings-item a:hover .writings-title { color: var(--accent); }

.writings-date {
    font-family: var(--font-mono);
    font-size: 0.74rem;
    letter-spacing: 0.08em;
    color: var(--ink-faint);
}

.writings-title {
    font-family: var(--font-display);
    font-size: clamp(1.1rem, 2vw, 1.35rem);
    font-weight: 500;
    line-height: 1.35;
    transition: color 0.2s ease;
}

.writings-cat {
    font-family: var(--font-mono);
    font-size: 0.66rem;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--ink-faint);
    white-space: nowrap;
}

@media (max-width: 640px) {
    .writings-item a { grid-template-columns: 1fr; gap: 0.3rem; }
}

.writings-more-wrap { margin-top: 2rem; }

/* ---------- media ---------- */

.media-grid {
    display: grid;
    grid-template-columns: minmax(0, 1.4fr) minmax(0, 1fr);
    gap: clamp(1.5rem, 4vw, 3rem);
    align-items: start;
}

.video-container {
    position: relative;
    aspect-ratio: 16 / 9;
    border: 1px solid var(--line-strong);
}

.video-container iframe {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    border: 0;
}

.media-note h3 {
    font-family: var(--font-display);
    font-size: 1.4rem;
    font-weight: 500;
    margin: 0.6rem 0 0.8rem;
    line-height: 1.3;
}

.media-note p { color: var(--ink-soft); font-size: 0.95rem; }

@media (max-width: 820px) {
    .media-grid { grid-template-columns: 1fr; }
}

/* ---------- contact ---------- */

.contact { text-align: left; }

.contact-big {
    font-family: var(--font-display);
    font-size: clamp(1.8rem, 4.5vw, 3.2rem);
    font-weight: 500;
    letter-spacing: -0.02em;
    line-height: 1.2;
    max-width: 22ch;
    margin-bottom: 2.2rem;
}

.contact-big .accent { color: var(--accent); font-style: italic; }

.contact-links { display: flex; gap: 1.25rem; flex-wrap: wrap; }

/* ---------- footer ---------- */

footer {
    padding: 2rem var(--pad);
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    flex-wrap: wrap;
    font-family: var(--font-mono);
    font-size: 0.7rem;
    letter-spacing: 0.1em;
    color: var(--ink-faint);
}

footer a { color: inherit; text-decoration: none; }
footer a:hover { color: var(--accent); }

/* ============================================================
   Writings index page (timeline)
   ============================================================ */

.page-header { padding: clamp(3.5rem, 8vw, 6rem) var(--pad) 0; }

.page-header h1 {
    font-family: var(--font-display);
    font-size: clamp(2.2rem, 5.5vw, 3.8rem);
    font-weight: 500;
    letter-spacing: -0.02em;
    margin: 1.2rem 0 1rem;
}

.page-header .page-sub { color: var(--ink-soft); max-width: 58ch; }

.cat-filters {
    display: flex;
    gap: 0.6rem;
    flex-wrap: wrap;
    padding: 2rem var(--pad) 0;
}

.cat-btn {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    background: none;
    border: 1px solid var(--line-strong);
    border-radius: 999px;
    color: var(--ink-soft);
    padding: 0.4rem 1rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

.cat-btn:hover { border-color: var(--accent); color: var(--accent); }
.cat-btn.active { background: var(--ink); border-color: var(--ink); color: var(--paper); }

.timeline { padding: clamp(2rem, 5vw, 3.5rem) var(--pad) clamp(3rem, 7vw, 5rem); }

.timeline-year {
    font-family: var(--font-display);
    font-style: italic;
    font-size: 1.5rem;
    color: var(--ink-faint);
    border-bottom: 1px solid var(--line-strong);
    padding-bottom: 0.6rem;
    margin: 2.5rem 0 0.5rem;
}

.timeline-year:first-child { margin-top: 0; }

.timeline-entry {
    display: grid;
    grid-template-columns: 6.5rem 1fr;
    gap: 1.5rem;
    padding: 1.6rem 0;
    border-bottom: 1px solid var(--line);
}

.timeline-date {
    font-family: var(--font-mono);
    font-size: 0.74rem;
    letter-spacing: 0.08em;
    color: var(--ink-faint);
    padding-top: 0.35rem;
}

.timeline-content h3 {
    font-family: var(--font-display);
    font-size: clamp(1.2rem, 2.2vw, 1.5rem);
    font-weight: 500;
    line-height: 1.3;
    margin: 0.5rem 0 0.6rem;
}

.timeline-content h3 a { text-decoration: none; transition: color 0.2s ease; }
.timeline-content h3 a:hover { color: var(--accent); }

.timeline-excerpt { color: var(--ink-soft); font-size: 0.95rem; max-width: 64ch; }

.timeline-meta {
    margin-top: 0.8rem;
    display: flex;
    gap: 1.2rem;
    font-family: var(--font-mono);
    font-size: 0.68rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    color: var(--ink-faint);
}

.timeline-tag {
    font-family: var(--font-mono);
    font-size: 0.66rem;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--accent);
}

@media (max-width: 640px) {
    .timeline-entry { grid-template-columns: 1fr; gap: 0.4rem; }
}

/* ============================================================
   Post page
   ============================================================ */

.post {
    max-width: 720px;
    margin: 0 auto;
    padding: clamp(3.5rem, 8vw, 6rem) var(--pad) clamp(3rem, 7vw, 5rem);
}

.post-meta {
    display: flex;
    gap: 1.2rem;
    align-items: baseline;
    font-family: var(--font-mono);
    font-size: 0.72rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    color: var(--ink-faint);
}

.post-meta .post-category { color: var(--accent); }

.post h1 {
    font-family: var(--font-display);
    font-size: clamp(1.9rem, 4.5vw, 3rem);
    font-weight: 500;
    letter-spacing: -0.02em;
    line-height: 1.18;
    margin: 1.2rem 0 2.5rem;
}

.post-body { font-size: 1.05rem; line-height: 1.9; }

.post-body p + p { margin-top: 1.3rem; }

.post-body h2 {
    font-family: var(--font-display);
    font-size: 1.55rem;
    font-weight: 500;
    letter-spacing: -0.01em;
    margin: 2.6rem 0 1rem;
    line-height: 1.3;
}

.post-body ul { margin: 1.3rem 0 1.3rem 1.3rem; }
.post-body li + li { margin-top: 0.5rem; }
.post-body strong { font-weight: 600; }

.post-body hr {
    border: none;
    border-top: 1px solid var(--line-strong);
    margin: 2.5rem 0;
}

.post-body em { color: var(--ink-soft); }

.post-footer {
    margin-top: 3.5rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--line-strong);
}

/* ---------- reveal helper (GSAP sets initial state in JS) ---------- */

[data-reveal] { will-change: transform, opacity; }

@media (prefers-reduced-motion: reduce) {
    html { scroll-behavior: auto; }
    *, *::before, *::after { transition: none !important; animation: none !important; }
}