:root {
    --black: #0a0a0a;
    --gray-900: #161616;
    --gray-700: #3d3d3d;
    --gray-500: #737373;
    --gray-300: #d4d4d4;
    --gray-100: #f2f2f2;
    --white: #ffffff;

    --radius-lg: 28px;
    --radius-md: 16px;
    --radius-pill: 999px;

    --container-w: 1140px;
    --transition: 0.25s ease;
}

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

html { scroll-behavior: smooth; }

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    color: var(--black);
    background: var(--white);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
ul { list-style: none; }

.container {
    max-width: var(--container-w);
    margin: 0 auto;
    padding: 0 24px;
}

section { position: relative; overflow: hidden; }

.eyebrow {
    text-transform: uppercase;
    letter-spacing: 0.14em;
    font-size: 0.75rem;
    font-weight: 700;
    color: var(--gray-500);
    margin-bottom: 12px;
}

.section-title {
    font-size: clamp(1.8rem, 3vw, 2.4rem);
    font-weight: 700;
    letter-spacing: -0.02em;
    margin-bottom: 48px;
    max-width: 620px;
}

/* Reveal-on-scroll */
.reveal {
    opacity: 0;
    transform: translateY(24px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}
.reveal.in-view {
    opacity: 1;
    transform: translateY(0);
}

/* Decorative blobs */
.blob {
    position: absolute;
    border-radius: 50%;
    border: 1px solid var(--gray-300);
    pointer-events: none;
    z-index: 0;
}
.blob-1 { width: 420px; height: 420px; top: -120px; right: -140px; }
.blob-2 { width: 260px; height: 260px; bottom: -80px; left: -100px; border-color: rgba(255,255,255,0.25); }
.blob-3 { width: 360px; height: 360px; top: -100px; left: 50%; transform: translateX(-50%); }

/* ==========================================================================
   Buttons
   ========================================================================== */

.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 14px 28px;
    border-radius: var(--radius-pill);
    font-weight: 600;
    font-size: 0.95rem;
    border: 1.5px solid var(--black);
    transition: background var(--transition), color var(--transition), transform var(--transition);
    white-space: nowrap;
}
.btn-solid { background: var(--black); color: var(--white); }
.btn-solid:hover { background: var(--gray-900); transform: translateY(-2px); }
.btn-outline { background: transparent; color: var(--black); }
.btn-outline:hover { background: var(--black); color: var(--white); transform: translateY(-2px); }
.btn-sm { padding: 9px 20px; font-size: 0.85rem; }
.btn-group { display: flex; flex-wrap: wrap; gap: 14px; }

/* ==========================================================================
   Header
   ========================================================================== */

.site-header {
    position: fixed;
    top: 0; left: 0; right: 0;
    z-index: 100;
    background: rgba(255,255,255,0.85);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid transparent;
    transition: border-color var(--transition), box-shadow var(--transition);
}
.site-header.scrolled {
    border-color: var(--gray-300);
    box-shadow: 0 4px 20px rgba(0,0,0,0.05);
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 76px;
}

.logo {
    font-weight: 800;
    font-size: 1.3rem;
    letter-spacing: -0.02em;
}
.logo span { color: var(--gray-500); }

.main-nav {
    display: flex;
    gap: 32px;
}
.nav-link {
    font-size: 0.92rem;
    font-weight: 500;
    color: var(--gray-700);
    position: relative;
    padding: 4px 0;
    transition: color var(--transition);
}
.nav-link::after {
    content: "";
    position: absolute;
    left: 0; bottom: -2px;
    width: 0; height: 2px;
    background: var(--black);
    transition: width var(--transition);
}
.nav-link:hover,
.nav-link.active { color: var(--black); }
.nav-link:hover::after,
.nav-link.active::after { width: 100%; }

.header-cta { flex-shrink: 0; }

.nav-toggle {
    display: none;
    flex-direction: column;
    justify-content: center;
    gap: 5px;
    width: 34px;
    height: 34px;
    background: none;
    border: none;
    cursor: pointer;
}
.nav-toggle span {
    display: block;
    height: 2px;
    background: var(--black);
    border-radius: 2px;
    transition: transform var(--transition), opacity var(--transition);
}
.nav-toggle.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle.open span:nth-child(2) { opacity: 0; }
.nav-toggle.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ==========================================================================
   Hero
   ========================================================================== */

.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding: 140px 0 80px;
    background: var(--black);
    color: var(--white);
}
.hero .blob { border-color: rgba(255,255,255,0.15); }

.hero-inner {
    display: grid;
    grid-template-columns: 1.1fr 0.9fr;
    gap: 48px;
    align-items: center;
    position: relative;
    z-index: 1;
}

.hero-text .eyebrow { color: var(--gray-300); }

.hero-text h1 {
    font-size: clamp(2.2rem, 5vw, 3.2rem);
    font-weight: 800;
    letter-spacing: -0.03em;
    line-height: 1.12;
    margin-bottom: 22px;
}

.hero-sub {
    color: var(--gray-300);
    max-width: 520px;
    margin-bottom: 32px;
    font-size: 1.02rem;
}

.hero .btn-outline { border-color: var(--white); color: var(--white); }
.hero .btn-outline:hover { background: var(--white); color: var(--black); }
.hero .btn-solid { background: var(--white); color: var(--black); border-color: var(--white); }
.hero .btn-solid:hover { background: var(--gray-100); }

.hero-media { display: flex; justify-content: center; }

.hero-photo-frame {
    position: relative;
    width: 100%;
    max-width: 380px;
    border-radius: var(--radius-lg);
    overflow: hidden;
    border: 1px solid rgba(255,255,255,0.25);
    aspect-ratio: 4 / 5;
}
.hero-photo {
    width: 100%;
    height: 100%;
    object-fit: cover;
    filter: grayscale(1) contrast(1.05);
}

.scroll-cue {
    position: absolute;
    bottom: 28px;
    left: 50%;
    transform: translateX(-50%);
    width: 40px;
    height: 40px;
    border: 1px solid rgba(255,255,255,0.4);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--white);
    animation: bounce 2.2s infinite;
    z-index: 1;
}
@keyframes bounce {
    0%, 100% { transform: translate(-50%, 0); }
    50% { transform: translate(-50%, 8px); }
}

/* ==========================================================================
   About
   ========================================================================== */

.about { padding: 110px 0; }

.about-inner {
    display: grid;
    grid-template-columns: 0.8fr 1.6fr;
    gap: 60px;
}

.signature {
    font-family: "Brush Script MT", "Segoe Script", cursive;
    font-size: 2.6rem;
    line-height: 1.1;
    text-align: center;
}
.signature-role {
    margin-top: 10px;
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    text-align: center;
}
.role-item {
    color: #d6d6d6;
    cursor: pointer;
    transition: color var(--transition);
}
.role-item:hover { text-decoration: underline; }
.role-item.active { color: #000; }
.role-sep { color: var(--gray-300); margin: 0 2px; }

.role-slider {
    margin: 24px auto 0;
    padding: 20px 20px 0;
    max-width: 340px;
    background: #fafafa;
    border: 1px solid var(--gray-300);
    border-radius: 10px;
}

.slider-track {
    position: relative;
    min-height: 110px;
}

.slide {
    position: absolute;
    top: 0; left: 0;
    width: 100%;
    font-size: 0.88rem;
    line-height: 1.55;
    color: var(--gray-700);
    text-align: center;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.5s ease;
}
.slide.active { opacity: 1; visibility: visible; }

.about-lead {
    font-size: 1.3rem;
    font-weight: 600;
    margin-bottom: 20px;
    letter-spacing: -0.01em;
}
.about-content p { color: var(--gray-700); margin-bottom: 16px; max-width: 640px; }
.text-link {
    color: var(--black);
    text-decoration: underline;
    transition: color var(--transition);
}
.text-link:hover { color: #1a4fd6; }

.quick-facts {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 20px 32px;
    margin-top: 32px;
    padding-top: 32px;
    border-top: 1px solid var(--gray-300);
    max-width: 640px;
}
.fact { font-size: 0.95rem; }
.fact span {
    display: block;
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--gray-500);
    margin-bottom: 4px;
}
.fact a:hover { text-decoration: underline; }

/* ==========================================================================
   Experience — timeline
   ========================================================================== */

.experience { padding: 110px 0; background: var(--gray-100); }

.timeline {
    position: relative;
    max-width: 760px;
    padding-left: 32px;
    border-left: 1px solid var(--gray-300);
}

.timeline-item {
    position: relative;
    padding-bottom: 44px;
}
.timeline-item:last-child { padding-bottom: 0; }

.timeline-marker {
    position: absolute;
    left: -37px;
    top: 4px;
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background: var(--white);
    border: 2px solid var(--black);
}
.timeline-marker.is-current { background: var(--black); }

.timeline-period {
    font-size: 0.78rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--gray-500);
}
.timeline-content h3 { font-size: 1.15rem; font-weight: 700; margin: 6px 0 2px; }
.timeline-company { font-size: 0.92rem; color: var(--gray-700); margin-bottom: 8px; font-weight: 500; }
.timeline-desc { font-size: 0.92rem; color: var(--gray-500); max-width: 600px; font-style: italic; }

/* ==========================================================================
   Education
   ========================================================================== */

.education { padding: 110px 0; }

.edu-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 24px;
}

.edu-card {
    padding: 32px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius-md);
    transition: border-color var(--transition), transform var(--transition);
}
.edu-card:hover { border-color: var(--black); transform: translateY(-4px); }

.edu-level {
    display: inline-block;
    font-size: 0.7rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    padding: 4px 12px;
    border-radius: var(--radius-pill);
    background: var(--black);
    color: var(--white);
    margin-bottom: 16px;
}
.edu-card h3 { font-size: 1.1rem; font-weight: 700; margin-bottom: 8px; line-height: 1.35; }
.edu-school { font-size: 0.92rem; color: var(--gray-700); margin-bottom: 4px; }
.edu-period { font-size: 0.85rem; color: var(--gray-500); }

/* ==========================================================================
   Skills
   ========================================================================== */

.skills { padding: 110px 0; background: var(--gray-100); }

.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 36px;
}
.skill-group h3 { font-size: 1rem; font-weight: 700; margin-bottom: 16px; }

.tag-list { display: flex; flex-wrap: wrap; gap: 10px; }
.tag {
    display: inline-block;
    padding: 8px 16px;
    font-size: 0.82rem;
    font-weight: 500;
    border-radius: var(--radius-pill);
    border: 1px solid var(--gray-300);
    background: var(--white);
    color: var(--gray-700);
}
.tag-dark { background: var(--black); color: var(--white); border-color: var(--black); }

/* ==========================================================================
   Research
   ========================================================================== */

.research { padding: 110px 0; }
.research .blob { border-color: var(--gray-300); }

.research-focus {
    display: grid;
    grid-template-columns: 1fr;
    gap: 20px;
    padding: 28px;
    border-radius: var(--radius-md);
    background: var(--black);
    color: var(--white);
    margin-bottom: 48px;
    position: relative;
    z-index: 1;
}
.focus-item span {
    display: block;
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--gray-300);
    margin-bottom: 8px;
}
.focus-item p { font-weight: 600; }

.pub-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 24px;
    position: relative;
    z-index: 1;
}

.pub-card {
    padding: 28px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius-md);
    display: flex;
    flex-direction: column;
    transition: border-color var(--transition), transform var(--transition);
}
.pub-card:hover { border-color: var(--black); transform: translateY(-4px); }
.pub-card .tag { align-self: flex-start; margin-bottom: 16px; }
.pub-card h3 { font-size: 1.02rem; font-weight: 700; line-height: 1.4; margin-bottom: 10px; }
.pub-authors { font-size: 0.85rem; color: var(--gray-700); margin-bottom: 4px; }
.pub-venue { font-size: 0.85rem; color: var(--gray-500); margin-bottom: 18px; font-style: italic; }
.pub-link { margin-top: auto; font-weight: 700; font-size: 0.88rem; }
.pub-link:not(.pub-link-disabled):hover { text-decoration: underline; }
.pub-link-disabled { color: var(--gray-300); cursor: default; }

/* ==========================================================================
   Contact
   ========================================================================== */

.contact { padding: 130px 0; background: var(--black); color: var(--white); text-align: center; }
.contact .eyebrow { color: var(--gray-300); }
.contact .section-title { margin: 0 auto 16px; }
.contact-sub { color: var(--gray-300); max-width: 480px; margin: 0 auto 36px; }
.contact-inner { display: flex; flex-direction: column; align-items: center; }
.contact .btn-group { justify-content: center; }
.contact .btn-outline { border-color: var(--white); color: var(--white); }
.contact .btn-outline:hover { background: var(--white); color: var(--black); }
.contact .btn-solid { background: var(--white); color: var(--black); border-color: var(--white); }
.contact .btn-solid:hover { background: var(--gray-100); }

/* ==========================================================================
   Footer
   ========================================================================== */

.site-footer { padding: 28px 0; }
.footer-inner {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 12px;
    font-size: 0.85rem;
    color: var(--gray-500);
}
.back-to-top { font-weight: 600; color: var(--black); transition: opacity var(--transition); }
.back-to-top:hover { opacity: 0.6; }

/* ==========================================================================
   Progress bar
   ========================================================================== */

.progress-bar {
    position: fixed;
    top: 0; left: 0;
    height: 3px;
    width: 0%;
    background: var(--black);
    z-index: 200;
    transition: width 0.1s linear;
}

/* ==========================================================================
   Responsive
   ========================================================================== */

@media (max-width: 900px) {
    .hero-inner { grid-template-columns: 1fr; text-align: center; }
    .hero-sub { margin-left: auto; margin-right: auto; }
    .hero-text .btn-group { justify-content: center; }
    .hero-media { order: -1; }
    .hero-photo-frame { max-width: 280px; }

    .about-inner { grid-template-columns: 1fr; gap: 32px; }
    .quick-facts { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 760px) {
    .main-nav {
        position: absolute;
        top: 76px;
        left: 0; right: 0;
        background: var(--white);
        border-bottom: 1px solid var(--gray-300);
        flex-direction: column;
        padding: 16px 24px;
        gap: 0;
        display: none;
    }
    .main-nav.open { display: flex; }
    .nav-link { padding: 12px 0; border-bottom: 1px solid var(--gray-100); }
    .nav-toggle { display: flex; }
    .header-cta { display: none; }

    .section-title { margin-bottom: 32px; }
    .quick-facts { grid-template-columns: 1fr; }
}