/* Leonard Yang Liu — personal site. Plain academic homepage. */

/* ---------- Type: self-hosted XCharter (matches the CV) ---------- */
@font-face {
    font-family: 'XCharter';
    src: url('fonts/XCharter-Roman.woff2') format('woff2');
    font-weight: 400; font-style: normal; font-display: swap;
}
@font-face {
    font-family: 'XCharter';
    src: url('fonts/XCharter-Italic.woff2') format('woff2');
    font-weight: 400; font-style: italic; font-display: swap;
}
@font-face {
    font-family: 'XCharter';
    src: url('fonts/XCharter-Bold.woff2') format('woff2');
    font-weight: 700; font-style: normal; font-display: swap;
}
@font-face {
    font-family: 'XCharter';
    src: url('fonts/XCharter-BoldItalic.woff2') format('woff2');
    font-weight: 700; font-style: italic; font-display: swap;
}

html { font-size: 19px; -webkit-text-size-adjust: 100%; scroll-behavior: smooth; background: var(--bg); }

:root {
    color-scheme: light dark;
    --bg: #ffffff;
    --fg: #1a1a1a;
    --fg-2: #2a2a2a;
    --fg-3: #4a4a4a;
    --muted: #5a5a5a;
    --faint: #888888;
    --faint-2: #999999;
    --copy: #b0b0b0;
    --sep: #aaaaaa;
    --accent: #1F3A68;
    --accent-hover: #0a1a3a;
    --progress: var(--accent);
    --line: #d0d0d0;
    --line-soft: #e0e0e0;
    --line-faint: #eeeeee;
    --line-table: #cccccc;
    --pdf-border: #c9d2e0;
    --nav-bg: rgba(255, 255, 255, 0.94);
}

/* Dark palette: applied when the system prefers dark (unless the visitor
   forced light), or when the visitor explicitly chose dark. */
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
        --bg: #15171c;
        --fg: #e3e3e3;
        --fg-2: #cfd1d4;
        --fg-3: #aab0b8;
        --muted: #9098a2;
        --faint: #7c828c;
        --faint-2: #6e757f;
        --copy: #6e757f;
        --sep: #4a4f57;
        --accent: #8bb0e6;
        --accent-hover: #b0caf2;
        --progress: #ffffff;
        --line: #333a45;
        --line-soft: #2a303a;
        --line-faint: #23272e;
        --line-table: #333a45;
        --pdf-border: #3a4762;
        --nav-bg: rgba(21, 23, 28, 0.9);
    }
}
:root[data-theme="dark"] {
    --bg: #15171c;
    --fg: #e3e3e3;
    --fg-2: #cfd1d4;
    --fg-3: #aab0b8;
    --muted: #9098a2;
    --faint: #7c828c;
    --faint-2: #6e757f;
    --copy: #6e757f;
    --sep: #4a4f57;
    --accent: #8bb0e6;
    --accent-hover: #b0caf2;
    --progress: #ffffff;
    --line: #333a45;
    --line-soft: #2a303a;
    --line-faint: #23272e;
    --line-table: #333a45;
    --pdf-border: #3a4762;
    --nav-bg: rgba(21, 23, 28, 0.9);
}

body {
    font-family: 'XCharter', Charter, 'Iowan Old Style', 'Source Serif Pro', 'Apple Garamond', Georgia, serif;
    line-height: 1.6;
    color: var(--fg);
    background: var(--bg);
    max-width: 1080px;
    margin: 0 auto;
    padding: 3rem 2rem 4rem;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

* { box-sizing: border-box; }

a { color: var(--accent); text-decoration: underline; text-underline-offset: 0.18em; text-decoration-thickness: 0.06em; }
a:hover { color: var(--accent-hover); }

img { max-width: 100%; display: block; }

/* ---------- Reading progress bar ---------- */
#progress {
    position: fixed;
    top: 0;
    left: 0;
    height: 2px;
    width: 0;
    background: var(--progress);
    z-index: 20;
    will-change: width;
}

/* ---------- Top nav ---------- */
.topnav {
    position: sticky;
    top: 0;
    z-index: 10;
    background: var(--nav-bg);
    backdrop-filter: saturate(180%) blur(8px);
    -webkit-backdrop-filter: saturate(180%) blur(8px);
    border-bottom: 1px solid var(--line-faint);
    margin: -3rem -2rem 2rem;
    padding: 0.75rem 2rem;
}
.topnav-inner {
    max-width: 1080px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    gap: 1.6rem;
    font-size: 0.9rem;
}
.topnav a {
    color: var(--fg-3);
    text-decoration: none;
    padding: 0.15rem 0;
    border-bottom: 1px solid transparent;
    transition: color .15s ease, border-color .15s ease;
}
.topnav a:hover {
    color: var(--fg);
    border-bottom-color: var(--fg);
}
.topnav a.active {
    color: var(--accent);
    border-bottom-color: var(--accent);
}

/* ---------- Light / dark toggle ---------- */
.theme-toggle {
    margin-left: auto;
    display: none;              /* shown only when JS is active */
    align-items: center;
    justify-content: center;
    width: 1.8rem;
    height: 1.8rem;
    background: none;
    border: 0;
    padding: 0;
    color: var(--fg-3);
    cursor: pointer;
    line-height: 0;
    border-radius: 4px;
    transition: color .15s ease;
}
html.js .theme-toggle { display: inline-flex; }
.theme-toggle:hover { color: var(--accent); }
.theme-toggle svg { width: 1.05rem; height: 1.05rem; display: block; }

/* ---------- Hero ---------- */
.hero {
    display: flex;
    gap: 2rem;
    align-items: flex-start;
    margin-bottom: 2.75rem;
}
.portrait {
    width: 165px;
    height: 205px;
    object-fit: cover;
    object-position: top center;
    flex-shrink: 0;
}
.hero-text { min-width: 0; }
.hero h1 {
    font-size: 1.95rem;
    font-weight: 600;
    margin: 0 0 0.6rem;
    line-height: 1.15;
    letter-spacing: -0.01em;
}
.hero .affil {
    margin: 0 0 0.9rem;
    color: var(--fg-2);
}
.hero .links {
    margin: 0 0 0.55rem;
    font-size: 0.95rem;
}
.hero .links .sep {
    color: var(--sep);
    margin: 0 0.45em;
}

/* ---------- Sections ---------- */
section { margin-top: 2.75rem; scroll-margin-top: 4.5rem; }

/* ---------- About ---------- */
#about p {
    margin: 0 0 0.95rem;
    line-height: 1.72;
}
#about p:last-child { margin-bottom: 0; }
#about p:first-of-type { font-size: 1.04rem; color: var(--fg); }
#about p:not(:first-of-type) { color: var(--fg-3); font-size: 0.98rem; }
#about p.market {
    margin-top: 1.4rem;
    color: var(--fg);
    font-style: italic;
    font-size: 1rem;
    border-left: 2px solid var(--accent);
    padding-left: 0.85rem;
}

h2 {
    position: relative;
    font-size: 1.05rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--fg);
    margin: 0 0 1.1rem;
    padding-bottom: 0.4rem;
    border-bottom: 1px solid var(--line);
}

/* Section heading deep-link (added by JS) */
.heading-anchor {
    margin-left: 0.45em;
    font-weight: 400;
    color: var(--faint-2);
    text-decoration: none;
    opacity: 0;
    transition: opacity .15s ease, color .15s ease;
}
h2:hover .heading-anchor,
.heading-anchor:focus-visible { opacity: 1; }
.heading-anchor:hover { color: var(--accent); }
.heading-anchor.copied { color: var(--accent); opacity: 1; }

/* ---------- Papers ---------- */
.papers {
    list-style: none;
    padding: 0;
    margin: 0;
    counter-reset: paper;
}
.paper {
    counter-increment: paper;
    margin-bottom: 2rem;
    padding-left: 2.2rem;
    position: relative;
}
.paper::before {
    content: "[" counter(paper) "]";
    position: absolute;
    left: 0;
    top: 0.18rem;
    font-family: 'XCharter', Charter, Georgia, serif;
    color: var(--faint-2);
    font-size: 0.95rem;
    font-variant-numeric: tabular-nums;
    transition: color .15s ease;
}
.paper:hover::before { color: var(--accent); }
.paper:last-child { margin-bottom: 0; }
.paper h3 {
    font-size: 1.06rem;
    font-weight: 600;
    margin: 0 0 0.3rem;
    line-height: 1.35;
}
.paper h3 .pdf-link {
    display: inline-block;
    margin-left: 0.5em;
    padding: 0.05em 0.45em;
    font-size: 0.72rem;
    font-weight: 600;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--accent);
    border: 1px solid var(--pdf-border);
    border-radius: 2px;
    text-decoration: none;
    vertical-align: 0.18em;
}
.paper h3 .pdf-link:hover {
    background: var(--accent);
    color: var(--bg);
    border-color: var(--accent);
}
.paper .byline {
    margin: 0 0 0.2rem;
    color: var(--fg);
    font-size: 0.98rem;
}
.paper .status {
    margin: 0 0 0.35rem;
    color: var(--fg-2);
    font-size: 0.95rem;
}
.paper .note {
    margin: 0 0 0.55rem;
    font-size: 0.92rem;
    color: var(--muted);
}
.paper .abstract {
    margin: 0.55rem 0 0;
}
.paper .abstract > summary {
    cursor: pointer;
    display: inline-block;
    font-size: 0.88rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    font-weight: 600;
    color: var(--accent);
    list-style: none;
    padding: 0.15rem 0;
    user-select: none;
}
.paper .abstract > summary::-webkit-details-marker { display: none; }
.paper .abstract > summary::before {
    content: "+";
    display: inline-block;
    width: 1em;
    color: var(--faint);
    font-weight: 400;
}
.paper .abstract[open] > summary::before { content: "\2212"; /* − */ }
.paper .abstract > summary:hover { color: var(--accent-hover); }
.paper .abstract > p {
    margin: 0.5rem 0 0;
    padding: 0 0 0 1rem;
    border-left: 2px solid var(--line-soft);
    color: var(--fg-2);
    font-size: 0.96rem;
    line-height: 1.6;
    text-align: justify;
    hyphens: auto;
}

/* ---------- Teaching ---------- */
.evals {
    border-collapse: collapse;
    margin: 1rem auto;
    font-size: 0.95rem;
}
.evals th, .evals td {
    padding: 0.35rem 1.75rem;
    text-align: center;
    font-weight: normal;
    font-variant-numeric: tabular-nums;
}
.evals th:first-child, .evals td:first-child { text-align: left; padding-left: 0; }
.evals th:last-child, .evals td:last-child { padding-right: 0; }
.evals thead th {
    border-bottom: 1px solid var(--line-table);
    color: var(--muted);
    font-size: 0.82rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    font-weight: 600;
}
.evals tbody td:first-child { color: var(--muted); }

.note {
    color: var(--muted);
    font-size: 0.92rem;
}

.subhead {
    font-size: 0.82rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--muted);
    margin: 1.5rem 0 0.6rem;
}
p.other-teaching {
    margin: 0 0 0.4rem;
    font-size: 0.96rem;
}
p.other-teaching:last-of-type { margin-bottom: 0; }

/* ---------- Contact ---------- */
.contact-list {
    display: grid;
    grid-template-columns: 5rem 1fr;
    gap: 0.35rem 1rem;
    margin: 0;
}
.contact-list dt {
    color: var(--muted);
    font-size: 0.86rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    font-weight: 600;
    padding-top: 0.1rem;
}
.contact-list dd { margin: 0; }

.copy-btn {
    font-family: inherit;
    font-size: 0.76rem;
    letter-spacing: 0.04em;
    text-transform: uppercase;
    color: var(--copy);
    background: none;
    border: 0;
    padding: 0;
    margin-left: 0.6rem;
    cursor: pointer;
    transition: color .15s ease;
    vertical-align: 0.04em;
}
.copy-btn:hover { color: var(--accent); }
.copy-btn.copied { color: var(--accent); }

/* ---------- Footer ---------- */
footer {
    margin-top: 3.5rem;
    padding-top: 1rem;
    border-top: 1px solid var(--line-faint);
    color: var(--faint);
    font-size: 0.85rem;
}

/* ---------- Focus (keyboard) ---------- */
a:focus-visible,
summary:focus-visible,
.copy-btn:focus-visible,
.theme-toggle:focus-visible,
.heading-anchor:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
    border-radius: 2px;
}

/* ---------- Scroll reveal (JS adds .reveal only to below-the-fold sections) ---------- */
main section.reveal { opacity: 0; transform: translateY(12px); transition: opacity .55s ease, transform .55s ease; }
main section.reveal.in { opacity: 1; transform: none; }

/* ---------- Reduced motion ---------- */
@media (prefers-reduced-motion: reduce) {
    html { scroll-behavior: auto; }
    *, *::before { transition: none !important; }
    main section.reveal { opacity: 1 !important; transform: none !important; }
}

/* ---------- Mobile ---------- */
@media (max-width: 560px) {
    body { padding: 2rem 1.25rem 3rem; }
    .hero {
        flex-direction: column;
        gap: 1.25rem;
    }
    .portrait { width: 130px; height: 165px; }
    .hero h1 { font-size: 1.65rem; }
    .paper { padding-left: 1.75rem; }
    .evals th, .evals td { padding-right: 1rem; }
    .contact-list { grid-template-columns: 1fr; gap: 0 0; }
    .contact-list dt { padding-top: 0.5rem; }
}

/* ---------- Print ---------- */
@media print {
    .topnav, #progress, .heading-anchor, .copy-btn, .theme-toggle { display: none; }
    body { max-width: none; margin: 0; padding: 0; color: #000; }
    a { color: #000; text-decoration: none; }
    .hero { margin-bottom: 1.5rem; }
    section { margin-top: 1.5rem; }
    .paper, section, .hero { page-break-inside: avoid; }
    .paper .abstract { display: none; }
    main section.reveal { opacity: 1 !important; transform: none !important; }
    footer { border: none; color: #000; margin-top: 2rem; }
}