/* ==========================================================================
   Xuefei (Julie) Wang — Personal Website
   Minimal & modern. Strong typography. Custom visual accent.
   ========================================================================== */

:root {
    --color-bg: #faf8f5;
    --color-text: #1a1a1c;
    --color-text-secondary: #71717a;
    --color-accent: #068aa1;
    --color-accent-hover: #046a7d;
    --color-accent-light: #e0f4f7;
    --color-accent-warm: #06a18a;
    --color-accent-cool: #0672a1;
    --color-border: #e4e1db;
    --color-border-light: #edebe6;

    --font-serif: 'EB Garamond', Georgia, 'Times New Roman', serif;
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;

    --max-width: 720px;
    --nav-height: 56px;
    --section-spacing: 6rem;
}

/* ---------- Dark Theme ---------- */

[data-theme="dark"] {
    --color-bg: #181820;
    --color-text: #e8e6e1;
    --color-text-secondary: #9ca3af;
    --color-accent: #0bb4cc;
    --color-accent-hover: #2ad0e8;
    --color-accent-light: rgba(6, 138, 161, 0.15);
    --color-accent-warm: #06a18a;
    --color-accent-cool: #0672a1;
    --color-border: #2e2e3a;
    --color-border-light: #252530;
}

[data-theme="dark"] .site-header {
    background: rgba(24, 24, 32, 0.85);
}

[data-theme="dark"] h1 {
    background: linear-gradient(135deg, var(--color-text) 0%, #0bb4cc 100%);
    -webkit-background-clip: text;
    background-clip: text;
}

[data-theme="dark"] .venue-tag.journal { background: #1a3325; color: #4ade80; }
[data-theme="dark"] .venue-tag.conference { background: #0f2a35; color: #38bdf8; }
[data-theme="dark"] .venue-tag.preprint { background: #2a2218; color: #d4a574; }

[data-theme="dark"] ::selection {
    color: #fff;
}

/* ---------- Reset ---------- */

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

html {
    scroll-behavior: smooth;
    scroll-padding-top: calc(var(--nav-height) + 2rem);
    overflow-x: hidden;
}

body {
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.75;
    color: var(--color-text);
    background: var(--color-bg);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow-x: hidden;
}

a {
    color: var(--color-accent);
    text-decoration: none;
    transition: color 0.25s ease;
}
a:hover { color: var(--color-accent-hover); }

img { max-width: 100%; display: block; }
strong { font-weight: 600; }

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

/* ---------- Navigation ---------- */

.site-header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(250, 248, 245, 0.85);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid transparent;
    transition: border-color 0.3s ease;
}

.site-header.scrolled {
    border-bottom-color: var(--color-border-light);
}

.nav {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 1.5rem;
    height: var(--nav-height);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-name {
    font-family: var(--font-serif);
    font-size: 1.15rem;
    font-weight: 500;
    color: var(--color-text);
    letter-spacing: -0.01em;
    transition: color 0.25s ease;
}
.nav-name:hover { color: var(--color-accent); }

.nav-links { display: flex; gap: 2rem; margin-left: 2rem; }

.nav-links a {
    font-size: 0.82rem;
    font-weight: 450;
    color: var(--color-text-secondary);
    letter-spacing: 0.02em;
    position: relative;
    transition: color 0.25s ease;
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 0;
    height: 1px;
    background: var(--color-accent);
    transition: width 0.3s ease;
}
.nav-links a:hover { color: var(--color-text); }
.nav-links a:hover::after { width: 100%; }

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
}
.nav-toggle span {
    display: block;
    width: 18px;
    height: 1.5px;
    background: var(--color-text);
    border-radius: 1px;
    transition: transform 0.3s ease;
}
.nav-toggle.active span:first-child { transform: translateY(3.25px) rotate(45deg); }
.nav-toggle.active span:last-child { transform: translateY(-3.25px) rotate(-45deg); }

/* ---------- Theme Toggle ---------- */

.theme-toggle {
    background: none;
    border: none;
    cursor: pointer;
    padding: 6px;
    border-radius: 8px;
    color: var(--color-text);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: color 0.25s ease, background-color 0.25s ease;
    margin-left: auto;
    margin-right: 0.75rem;
}
.theme-toggle:hover {
    color: var(--color-accent);
    background: var(--color-accent-light);
}
.theme-toggle svg { width: 20px; height: 20px; }
.theme-toggle .icon-sun { display: none; }
.theme-toggle .icon-moon { display: block; }
[data-theme="dark"] .theme-toggle .icon-sun { display: block; }
[data-theme="dark"] .theme-toggle .icon-moon { display: none; }

/* ---------- Layout ---------- */

main {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 1.5rem;
}

.section { padding-top: var(--section-spacing); }
.section:last-child { padding-bottom: var(--section-spacing); }

/* ---------- Strong Section Headings ---------- */

h2 {
    font-family: var(--font-serif);
    font-size: 1.85rem;
    font-weight: 500;
    letter-spacing: -0.025em;
    margin-bottom: 0.5rem;
    color: var(--color-text);
    position: relative;
    display: inline-block;
}

h2::after {
    content: '';
    display: block;
    width: 32px;
    height: 2.5px;
    background: linear-gradient(90deg, var(--color-accent), var(--color-accent-warm));
    border-radius: 2px;
    margin-top: 0.4rem;
    margin-bottom: 1.5rem;
}

.section-note {
    font-size: 0.82rem;
    color: var(--color-text-secondary);
    margin-bottom: 1.75rem;
}

/* ---------- Scroll Animations ---------- */

.animate-in {
    opacity: 0;
    transform: translateY(28px);
    transition: opacity 0.8s cubic-bezier(0.16, 1, 0.3, 1),
                transform 0.8s cubic-bezier(0.16, 1, 0.3, 1);
}

.animate-in.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ---------- About Section ---------- */

.about-section {
    padding-top: 4.5rem;
    padding-bottom: 1rem;
    position: relative;
    overflow: hidden;
}

/* Interactive canvas background */
#snowflake-canvas {
    position: absolute;
    top: -60px;
    left: -100px;
    right: -100px;
    bottom: -60px;
    width: calc(100% + 200px);
    height: calc(100% + 120px);
    pointer-events: none;
    z-index: 0;
    opacity: 0;
    transition: opacity 1.5s ease;
}

#snowflake-canvas.loaded {
    opacity: 1;
}

/* Hero load animation */
.hero-animate .about-grid {
    opacity: 0;
    transform: translateY(24px);
    transition: opacity 0.9s cubic-bezier(0.16, 1, 0.3, 1) 0.15s,
                transform 0.9s cubic-bezier(0.16, 1, 0.3, 1) 0.15s;
}

.hero-visible .about-grid {
    opacity: 1;
    transform: translateY(0);
}

.about-grid {
    display: grid;
    grid-template-columns: 180px 1fr;
    gap: 2.75rem;
    align-items: start;
    position: relative;
    z-index: 1;
}

.profile-photo-wrapper { position: relative; }

.profile-photo {
    width: 180px;
    height: 180px;
    border-radius: 14px;
    object-fit: cover;
    transition: transform 0.5s cubic-bezier(0.16, 1, 0.3, 1),
                box-shadow 0.5s ease;
}
.profile-photo:hover {
    transform: scale(1.02);
    box-shadow: 0 8px 30px rgba(6, 138, 161, 0.12);
}

.photo-placeholder {
    width: 180px;
    height: 180px;
    border-radius: 14px;
    background: linear-gradient(145deg, #0bbcd9 0%, #068aa1 40%, #06a18a 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: var(--font-serif);
    font-size: 3.2rem;
    font-weight: 500;
    color: rgba(255, 255, 255, 0.9);
    letter-spacing: 0.04em;
}

/* ---------- Strong Name Typography ---------- */

h1 {
    font-family: var(--font-serif);
    font-size: 2.8rem;
    font-weight: 600;
    letter-spacing: -0.035em;
    line-height: 1.1;
    margin-bottom: 0.35rem;
    background: linear-gradient(135deg, #1a3a4a 0%, #0bb4cc 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.role {
    color: var(--color-text-secondary);
    font-weight: 400;
    letter-spacing: 0.02em;
    text-transform: uppercase;
    font-variant-caps: all-small-caps;
    font-size: 0.98rem;
}

.affiliation {
    font-family: var(--font-serif);
    font-size: 1.05rem;
    font-style: italic;
    color: var(--color-text-secondary);
    font-weight: 400;
    margin-bottom: 1rem;
}

/* Social Links */
.social-links {
    display: flex;
    gap: 0.35rem;
    margin-bottom: 1.5rem;
}

.social-links a {
    width: 34px;
    height: 34px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--color-text-secondary);
    border-radius: 8px;
    transition: color 0.25s ease, background-color 0.25s ease, transform 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}
.social-links a:hover {
    color: var(--color-accent);
    background: var(--color-accent-light);
    transform: translateY(-2px);
}
.social-links svg { width: 17px; height: 17px; }

/* Bio */
.bio p {
    margin-bottom: 0.6rem;
    font-size: 0.93rem;
    line-height: 1.75;
}
.bio p:last-child { margin-bottom: 0; }

.bio a {
    text-decoration-line: underline;
    text-decoration-color: var(--color-border);
    text-underline-offset: 3px;
    text-decoration-thickness: 1px;
    transition: text-decoration-color 0.25s ease, color 0.25s ease;
}
.bio a:hover { text-decoration-color: var(--color-accent); }

/* ---------- News ---------- */

.news-list { list-style: none; }

.news-list li {
    display: flex;
    gap: 1.25rem;
    padding: 0.6rem 0;
    font-size: 0.9rem;
    align-items: baseline;
}
.news-list li + li { border-top: 1px solid var(--color-border-light); }

.news-date {
    flex-shrink: 0;
    width: 80px;
    color: var(--color-text-secondary);
    font-size: 0.82rem;
    font-weight: 500;
    letter-spacing: 0.01em;
}

.news-text { flex: 1; }
.news-text a {
    text-decoration-line: underline;
    text-decoration-color: var(--color-border);
    text-underline-offset: 3px;
    text-decoration-thickness: 1px;
}
.news-text a:hover { text-decoration-color: var(--color-accent); }

.news-hidden { display: none; }

/* ---------- Publications ---------- */

.pub-list {
    list-style: none;
}

.pub-item {
    padding: 1.1rem 0;
    border-radius: 6px;
}
.pub-item + .pub-item { border-top: 1px solid var(--color-border-light); }

.pub-item.first-author {
    border-left: 2.5px solid var(--color-accent);
    padding-left: 1.1rem;
    margin-left: -1.1rem;
    border-top: none;
}
.pub-item.first-author + .pub-item { border-top: none; }

.pub-title {
    font-weight: 500;
    font-size: 0.93rem;
    line-height: 1.55;
    margin-bottom: 0.2rem;
    letter-spacing: -0.005em;
}

.pub-authors {
    font-size: 0.82rem;
    color: var(--color-text-secondary);
    line-height: 1.55;
    margin-bottom: 0.2rem;
}

.pub-venue {
    font-size: 0.82rem;
    color: var(--color-text-secondary);
    margin-bottom: 0.4rem;
    display: flex;
    align-items: center;
    gap: 0.4rem;
}

.venue-tag {
    display: inline-block;
    font-size: 0.65rem;
    font-weight: 600;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    padding: 1px 7px;
    border-radius: 3px;
    line-height: 1.7;
}
.venue-tag.journal { background: #e6f4ea; color: #1e7e34; }
.venue-tag.conference { background: #dceef5; color: #067a94; }
.venue-tag.preprint { background: #f0e6db; color: #9a6030; }

.pub-links { display: flex; gap: 0.45rem; flex-wrap: wrap; }
.pub-links a {
    font-size: 0.78rem;
    font-weight: 500;
    color: var(--color-accent);
    padding: 2px 10px;
    border: 1px solid var(--color-border);
    border-radius: 4px;
    transition: all 0.25s ease;
}
.pub-links a:hover {
    border-color: var(--color-accent);
    background: var(--color-accent-light);
    transform: translateY(-1px);
}

.pub-hidden { display: none; }

/* ---------- Toggle Button ---------- */

.toggle-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    margin-top: 1rem;
    padding: 0.4rem 0;
    background: none;
    border: none;
    font-family: var(--font-sans);
    font-size: 0.82rem;
    font-weight: 500;
    color: var(--color-accent);
    cursor: pointer;
    transition: color 0.25s ease;
}
.toggle-btn:hover { color: var(--color-accent-hover); }

.toggle-icon {
    width: 15px;
    height: 15px;
    transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}
.toggle-btn.expanded .toggle-icon { transform: rotate(180deg); }

/* ---------- Teaching ---------- */

.teaching-list { list-style: none; }

.teaching-list li {
    display: flex;
    flex-wrap: wrap;
    gap: 0.25rem 0.6rem;
    padding: 0.65rem 0;
    font-size: 0.9rem;
    align-items: baseline;
}
.teaching-list li + li { border-top: 1px solid var(--color-border-light); }

.teaching-role {
    font-weight: 600;
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--color-accent);
    background: var(--color-accent-light);
    padding: 1px 8px;
    border-radius: 3px;
    flex-shrink: 0;
}
.teaching-course { flex: 1; min-width: 200px; }
.teaching-where { color: var(--color-text-secondary); font-size: 0.85rem; }
.teaching-when { color: var(--color-text-secondary); font-size: 0.85rem; flex-shrink: 0; margin-left: auto; }

/* ---------- Beyond Research ---------- */

.beyond-text {
    font-size: 0.93rem;
    line-height: 1.75;
    max-width: 600px;
}

.beyond-text a {
    text-decoration-line: underline;
    text-decoration-color: var(--color-border);
    text-underline-offset: 3px;
    text-decoration-thickness: 1px;
    transition: text-decoration-color 0.25s ease, color 0.25s ease;
}
.beyond-text a:hover { text-decoration-color: var(--color-accent); }

.chinese-name {
    font-size: 1.05em;
    font-weight: 500;
    color: var(--color-accent);
}

/* ---------- Footer ---------- */

.site-footer { padding: 2.5rem 1.5rem; text-align: center; }
.site-footer p { font-size: 0.78rem; color: var(--color-text-secondary); letter-spacing: 0.02em; }

/* ---------- Responsive ---------- */

@media (max-width: 640px) {
    :root { --section-spacing: 4rem; }

    .nav-links {
        display: none;
        position: absolute;
        top: var(--nav-height);
        left: 0; right: 0;
        flex-direction: column;
        padding: 1rem 1.5rem 1.25rem;
        gap: 0.8rem;
        border-bottom: 1px solid var(--color-border-light);
        background: rgba(250, 248, 245, 0.96);
        backdrop-filter: blur(16px);
        -webkit-backdrop-filter: blur(16px);
    }
    [data-theme="dark"] .nav-links {
        background: rgba(24, 24, 32, 0.96);
    }
    .nav-links.open { display: flex; }
    .nav-toggle { display: flex; }

    .about-grid { grid-template-columns: 1fr; gap: 1.75rem; }
    .profile-photo-wrapper { display: flex; justify-content: center; }
    .profile-photo, .photo-placeholder { width: 140px; height: 140px; }

    h1 { font-size: 2.2rem; }
    h2 { font-size: 1.5rem; }

    .social-links { justify-content: flex-start; }
    .news-list li { flex-direction: column; gap: 0.1rem; }
    .news-date { width: auto; }
    .teaching-list li { flex-direction: column; gap: 0.15rem; }
    .teaching-when { margin-left: 0; }
    .pub-item.first-author { margin-left: 0; }

    #snowflake-canvas { left: -50px; right: -50px; width: calc(100% + 100px); }
}

/* ---------- Print ---------- */

@media print {
    :root {
        --color-bg: #fff;
        --color-text: #1a1a1c;
        --color-text-secondary: #71717a;
        --color-accent: #068aa1;
        --color-border: #e4e1db;
        --color-border-light: #edebe6;
    }
    .site-header, .toggle-btn, .nav-toggle, .theme-toggle, #snowflake-canvas { display: none !important; }
    .news-hidden, .pub-hidden { display: flex !important; }
    .animate-in { opacity: 1 !important; transform: none !important; }
    body { font-size: 12px; background: #fff; color: #1a1a1c; }
    h1 { -webkit-text-fill-color: #1a1a1c; background: none; }
    .pub-item.first-author { border-left-color: #000; }
    .venue-tag.journal { background: #e6f4ea !important; color: #1e7e34 !important; }
    .venue-tag.conference { background: #dceef5 !important; color: #067a94 !important; }
    .venue-tag.preprint { background: #f0e6db !important; color: #9a6030 !important; }
}