/* ==========================================================
   dhruvk19.com v3: single-page portfolio
   ========================================================== */

:root {
    --bg: #121212;
    --surface: #1a1a1a;
    --surface-2: #222222;
    --border: rgba(255, 255, 255, 0.08);
    --border-strong: rgba(255, 255, 255, 0.16);
    --text: #ececec;
    --text-muted: #a1a1a1;
    --text-faint: #8a8a8a;

    /* Section accents carried over from v1/v2 */
    --orange: #d4915d;
    --green: #7fb069;
    --blue: #5a9fd4;
    --pink: #d9779a;
    --yellow: #e2c25c;

    --accent: var(--text);
    --header-bg: rgba(18, 18, 18, 0.78);

    color-scheme: dark;

    --font-display: 'Fraunces', Georgia, serif;
    --font-body: 'Inter', system-ui, -apple-system, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', ui-monospace, 'SF Mono', Menlo, monospace;

    --wrap: 1120px;
    --gutter: 40px;
    --header-h: 64px;
    --radius: 12px;
}

/* Light theme: set on <html> by the inline script in <head>, toggled by the
   nav button. Accents are darkened to keep text contrast at WCAG AA. */
:root[data-theme="light"] {
    --bg: #faf9f6;
    --surface: #ffffff;
    --surface-2: #f0efeb;
    --border: rgba(0, 0, 0, 0.09);
    --border-strong: rgba(0, 0, 0, 0.18);
    --text: #1a1a1a;
    --text-muted: #4f4f4f;
    --text-faint: #6b6b6b;

    --orange: #a3552a;
    --green: #3d7529;
    --blue: #2c6aa3;
    --pink: #ad3d67;
    --yellow: #846810;

    --header-bg: rgba(250, 249, 246, 0.82);

    color-scheme: light;
}

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

* {
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: calc(var(--header-h) + 16px);
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font-body);
    font-size: 17px;
    line-height: 1.65;
    color: var(--text);
    background-color: var(--bg);
    -webkit-font-smoothing: antialiased;
    overflow-x: hidden;
}

ul,
ol {
    list-style: none;
}

a {
    color: inherit;
    text-decoration: none;
}

strong {
    font-weight: 600;
    color: var(--text);
}

.wrap {
    max-width: var(--wrap);
    margin: 0 auto;
    padding: 0 var(--gutter);
}

.mono {
    font-family: var(--font-mono);
    font-size: 0.8em;
}

:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 3px;
    border-radius: 4px;
}

.skip-link {
    position: absolute;
    left: 16px;
    top: -48px;
    z-index: 100;
    padding: 8px 14px;
    background: var(--text);
    color: var(--bg);
    border-radius: 6px;
    font-weight: 600;
    transition: top 0.2s ease;
}

.skip-link:focus {
    top: 12px;
}

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

.site-header {
    position: sticky;
    top: 0;
    z-index: 50;
    height: var(--header-h);
    background: var(--header-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid transparent;
    transition: border-color 0.3s ease;
}

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

.nav {
    max-width: var(--wrap);
    height: 100%;
    margin: 0 auto;
    padding: 0 var(--gutter);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
}

.nav-brand {
    font-family: var(--font-display);
    font-size: 1.25rem;
    font-weight: 400;
    white-space: nowrap;
}

.nav-links {
    display: flex;
    gap: 28px;
}

.nav-links {
    position: relative;
    margin-left: auto;
}

.nav-links a {
    position: relative;
    display: inline-block;
    font-size: 0.95rem;
    color: var(--text-muted);
    padding: 6px 0 8px;
    transition: color 0.2s ease;
}

/* hover underline (the active section uses the sliding indicator below) */
.nav-links a::after {
    content: "";
    position: absolute;
    left: 0;
    bottom: 2px;
    width: 0;
    height: 2px;
    border-radius: 2px;
    background: currentColor;
    opacity: 0.5;
    transition: width 0.25s ease;
}

.nav-links a[data-accent="orange"] { --link: var(--orange); }
.nav-links a[data-accent="green"]  { --link: var(--green); }
.nav-links a[data-accent="blue"]   { --link: var(--blue); }
.nav-links a[data-accent="pink"]   { --link: var(--pink); }
.nav-links a[data-accent="yellow"] { --link: var(--yellow); }

.nav-links a:hover,
.nav-links a.is-current {
    color: var(--link);
}

.nav-links a:hover:not(.is-current)::after {
    width: 100%;
}

/* scrollspy indicator: slides between links; positioned by js/main.js */
.nav-links::before {
    content: "";
    position: absolute;
    left: 0;
    bottom: 2px;
    height: 2px;
    border-radius: 2px;
    width: var(--ind-w, 0);
    transform: translateX(var(--ind-x, 0));
    background: var(--ind-color, transparent);
    opacity: var(--ind-o, 0);
    transition: transform 0.35s cubic-bezier(0.4, 0, 0.2, 1), width 0.35s cubic-bezier(0.4, 0, 0.2, 1), background-color 0.35s ease, opacity 0.25s ease;
    pointer-events: none;
}

/* light/dark toggle */
.theme-toggle {
    flex-shrink: 0;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    color: var(--text-muted);
    background: transparent;
    border: 1px solid var(--border-strong);
    border-radius: 999px;
    cursor: pointer;
    transition: color 0.2s ease, border-color 0.2s ease;
}

.theme-toggle:hover {
    color: var(--text);
    border-color: var(--text-muted);
}

.theme-toggle svg {
    width: 18px;
    height: 18px;
}

/* show the sun in dark mode (switch to light), the moon in light mode */
.theme-toggle .icon-moon,
:root[data-theme="light"] .theme-toggle .icon-sun {
    display: none;
}

:root[data-theme="light"] .theme-toggle .icon-moon {
    display: block;
}

/* ---------- Hero ---------- */

.hero {
    position: relative;
    min-height: calc(100svh - var(--header-h));
    display: flex;
    align-items: center;
    padding: 72px 0 96px;
    overflow: hidden;
}

.hero .wrap {
    position: relative;
    width: 100%;
}

.eyebrow {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    letter-spacing: 0.04em;
    color: var(--text-muted);
    margin-bottom: 20px;
}

.hero-title {
    font-family: var(--font-display);
    font-weight: 300;
    font-size: clamp(3.5rem, 11vw, 8rem);
    line-height: 0.95;
    letter-spacing: -0.03em;
    text-transform: lowercase;
    margin-bottom: 32px;
}

.hero-title .dot {
    color: var(--orange);
}

.hero-lede {
    max-width: 640px;
    font-size: clamp(1.15rem, 2.2vw, 1.4rem);
    line-height: 1.5;
    color: var(--text-muted);
    margin-bottom: 16px;
}

.hero-sub {
    max-width: 640px;
    font-size: 0.95rem;
    color: var(--text-faint);
    margin-bottom: 40px;
}

.hero-sub strong {
    color: var(--text-muted);
}

.hero-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
}

.btn {
    display: inline-flex;
    align-items: center;
    padding: 11px 20px;
    border-radius: 999px;
    border: 1px solid var(--border-strong);
    font-size: 0.95rem;
    font-weight: 500;
    transition: background-color 0.2s ease, border-color 0.2s ease, color 0.2s ease, transform 0.2s ease;
}

.btn:hover {
    border-color: var(--text-muted);
    transform: translateY(-1px);
}

.btn-primary {
    background: var(--text);
    color: var(--bg);
    border-color: var(--text);
}

.btn-primary:hover {
    background: var(--orange);
    border-color: var(--orange);
}

/* ---------- Sections ---------- */

.section {
    padding: 112px 0;
    border-top: 1px solid var(--border);
}

.accent-orange { --accent: var(--orange); }
.accent-green  { --accent: var(--green); }
.accent-blue   { --accent: var(--blue); }
.accent-pink   { --accent: var(--pink); }
.accent-yellow { --accent: var(--yellow); }

.section-head {
    display: flex;
    align-items: baseline;
    gap: 16px;
    margin-bottom: 48px;
}

.section-num {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--accent);
}

.section-head h2 {
    font-family: var(--font-display);
    font-weight: 300;
    font-size: clamp(2.5rem, 6vw, 3.75rem);
    line-height: 1;
    letter-spacing: -0.02em;
    color: var(--accent);
}

.section-tagline {
    font-family: var(--font-display);
    font-style: italic;
    font-size: 1.15rem;
    color: var(--text-muted);
    margin: -24px 0 32px;
}

.subhead {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    font-weight: 500;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--accent);
    margin-bottom: 16px;
}

a:not(.btn):not(.nav-brand):not(.contact-email) {
    transition: color 0.2s ease;
}

.about-text a,
.role-body a,
.pub-links a,
.card-links a,
.profile-links a {
    color: var(--text);
    text-decoration: underline;
    text-decoration-color: color-mix(in srgb, var(--accent) 60%, transparent);
    text-decoration-thickness: 1px;
    text-underline-offset: 4px;
}

.about-text a:hover,
.role-body a:hover,
.pub-links a:hover,
.card-links a:hover,
.profile-links a:hover {
    color: var(--accent);
}

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

.about-grid {
    display: grid;
    grid-template-columns: minmax(0, 1.6fr) minmax(0, 1fr);
    gap: 64px;
    align-items: start;
}

.about-text > p {
    font-size: 1.1rem;
    color: var(--text-muted);
    margin-bottom: 20px;
    max-width: 62ch;
}

.about-text .subhead {
    margin-top: 40px;
}

.course-list li {
    display: flex;
    justify-content: space-between;
    gap: 16px;
    padding: 12px 0;
    border-bottom: 1px solid var(--border);
}

.course-list li .mono {
    color: var(--text-faint);
    text-align: right;
    white-space: nowrap;
}

.edu-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 28px;
    position: sticky;
    top: calc(var(--header-h) + 24px);
}

.edu-item {
    padding-bottom: 20px;
    margin-bottom: 20px;
    border-bottom: 1px solid var(--border);
}

.edu-school {
    font-family: var(--font-display);
    font-size: 1.2rem;
}

.edu-degree {
    font-weight: 500;
}

.edu-detail {
    font-size: 0.9rem;
    color: var(--text-muted);
}

.edu-gpa {
    font-size: 1.1rem;
}

.edu-gpa .mono {
    color: var(--accent);
    margin-right: 8px;
}

/* ---------- Experience timeline ---------- */

.timeline {
    position: relative;
}

.role {
    display: grid;
    grid-template-columns: 180px minmax(0, 1fr);
    gap: 40px;
    padding: 36px 0;
    border-bottom: 1px solid var(--border);
}

.role:first-child {
    padding-top: 0;
}

.role:last-child {
    border-bottom: none;
}

.role-meta time {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--accent);
}

.role-place {
    font-size: 0.85rem;
    color: var(--text-faint);
}

.role-body h3 {
    font-family: var(--font-display);
    font-weight: 400;
    font-size: 1.5rem;
    line-height: 1.25;
}

.role-body .at {
    color: var(--text-muted);
}

.role-team {
    color: var(--text-faint);
    font-size: 0.95rem;
    margin: 4px 0 16px;
}

.role-body > ul:not(.tags) li {
    position: relative;
    padding-left: 20px;
    color: var(--text-muted);
    margin-bottom: 8px;
}

.role-body > ul:not(.tags) li::before {
    content: "";
    position: absolute;
    left: 2px;
    top: 0.72em;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--accent);
}

/* ---------- Tags ---------- */

.tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 18px;
}

.tags li {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--text-muted);
    padding: 4px 10px;
    border-radius: 999px;
    background: color-mix(in srgb, var(--accent) 10%, transparent);
    border: 1px solid color-mix(in srgb, var(--accent) 22%, transparent);
}

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

.pub-list {
    display: grid;
    gap: 20px;
}

.pub {
    background: var(--surface);
    border: 1px solid var(--border);
    border-left: 3px solid var(--accent);
    border-radius: var(--radius);
    padding: 28px 32px;
}

.pub-venue {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--accent);
    margin-bottom: 8px;
}

.pub h3 {
    font-family: var(--font-display);
    font-weight: 400;
    font-size: 1.4rem;
    line-height: 1.3;
    margin-bottom: 10px;
}

.pub-authors,
.pub-desc {
    color: var(--text-muted);
    font-size: 0.95rem;
}

.pub-links,
.card-links,
.profile-links {
    display: flex;
    flex-wrap: wrap;
    gap: 8px 22px;
    margin-top: 16px;
    font-size: 0.95rem;
}

.section .profile-links {
    margin-top: 32px;
}

/* ---------- Projects ---------- */

.filters {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 32px;
}

.filter {
    font: inherit;
    font-size: 0.9rem;
    color: var(--text-muted);
    background: transparent;
    border: 1px solid var(--border-strong);
    border-radius: 999px;
    padding: 6px 16px;
    cursor: pointer;
    transition: all 0.2s ease;
}

.filter:hover {
    color: var(--text);
}

.filter.is-active {
    color: var(--bg);
    background: var(--accent);
    border-color: var(--accent);
}

/* masonry: cards stack directly under each other in each column */
.project-grid {
    columns: 320px 3;
    column-gap: 20px;
}

.card {
    display: inline-block;
    width: 100%;
    vertical-align: top;
    break-inside: avoid;
    margin-bottom: 20px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 26px;
    transition: border-color 0.25s ease, transform 0.25s ease, background-color 0.25s ease;
}

.card:hover {
    border-color: color-mix(in srgb, var(--accent) 45%, transparent);
    background: var(--surface-2);
}

.card[hidden] {
    display: none;
}

.card h3 {
    font-family: var(--font-display);
    font-weight: 400;
    font-size: 1.3rem;
    line-height: 1.3;
    color: var(--accent);
    margin-bottom: 12px;
}

.card p {
    font-size: 0.95rem;
    color: var(--text-muted);
}

.card-archive {
    border-style: dashed;
}

/* ---------- Contact ---------- */

.contact-lede {
    font-size: 1.15rem;
    color: var(--text-muted);
    margin-bottom: 16px;
}

.contact-email {
    display: inline-block;
    font-family: var(--font-display);
    font-weight: 300;
    font-size: clamp(1.75rem, 5vw, 3rem);
    letter-spacing: -0.01em;
    border-bottom: 2px solid var(--accent);
    transition: color 0.2s ease;
}

.contact-email:hover {
    color: var(--accent);
}

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

.site-footer {
    padding: 32px 0 48px;
    border-top: 1px solid var(--border);
    font-size: 0.9rem;
    color: var(--text-faint);
}

/* ---------- Reveal on scroll (only when JS is running) ---------- */

.js .reveal {
    opacity: 0;
    transform: translateY(16px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

.js .reveal.is-visible {
    opacity: 1;
    transform: none;
}

@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }

    .js .reveal {
        opacity: 1;
        transform: none;
        transition: none;
    }

    .btn:hover {
        transform: none;
    }

    .nav-links::before {
        transition: none;
    }
}

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

@media (max-width: 900px) {
    .about-grid {
        grid-template-columns: 1fr;
        gap: 40px;
    }

    .edu-card {
        position: static;
    }

    .role {
        grid-template-columns: 1fr;
        gap: 8px;
    }
}

@media (max-width: 700px) {
    :root {
        --gutter: 16px;
        --header-h: 56px;
    }

    body {
        font-size: 16px;
    }

    .nav {
        gap: 12px;
    }

    .theme-toggle {
        width: 36px;
        height: 36px;
    }

    .nav-brand {
        font-size: 1.1rem;
    }

    /* scrollable link row on small screens */
    .nav-links {
        gap: 18px;
        overflow-x: auto;
        scrollbar-width: none;
        -webkit-mask-image: linear-gradient(to right, #000 85%, transparent);
        mask-image: linear-gradient(to right, #000 85%, transparent);
        padding-right: 24px;
    }

    .nav-links::-webkit-scrollbar {
        display: none;
    }

    .nav-links a {
        font-size: 0.9rem;
        white-space: nowrap;
    }

    .hero {
        padding: 48px 0 72px;
        min-height: auto;
    }

    .section {
        padding: 80px 0;
    }

    .section-head {
        margin-bottom: 32px;
    }

    .project-grid {
        columns: 1;
    }

    .pub {
        padding: 22px;
    }

    .course-list li {
        flex-direction: column;
        gap: 2px;
    }

    .course-list li .mono {
        text-align: left;
        white-space: normal;
    }
}