/* ============================================================
   Sugeerth Murugesan — Portfolio
   Vanilla CSS · refined modern dark theme · bento-influenced
   ============================================================ */

:root {
  /* Theme-independent design tokens */
  --radius:      18px;
  --radius-lg:   22px;
  --radius-sm:   11px;
  --maxw:        1200px;
  --ease:        cubic-bezier(.22, 1, .36, 1);
  --display:     'Space Grotesk', 'Inter', system-ui, sans-serif;
  --mono:        'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, monospace;
}

/* ============================================================
   LIGHT THEME (default) — soft off-white, calm surfaces
   ============================================================ */
:root,
:root[data-theme="light"] {
  /* Surfaces — soft off-white, never stark pure white */
  --bg:          #f4f2ee;
  --bg-soft:     #efece6;
  --bg-card:     #ffffff;
  --bg-card-solid: #ffffff;
  --bg-elev:     #f3f1ec;
  --bg-elev-hi:  #e9e6df;

  /* Borders */
  --border:      #e2ddd3;
  --border-soft: #d3cdc0;
  --border-hi:   #bdb5a3;

  /* Text hierarchy — dark, high-contrast on light */
  --text:        #1d2230;
  --text-dim:    #51596d;
  --text-faint:  #5b6274;

  /* Accent — deepened so it's readable on light surfaces */
  --accent:      #5d4ce0;
  --accent-hi:   #4a3bc7;
  --accent-2:    #0a7064;
  --accent-soft: rgba(93, 76, 224, 0.10);
  --accent-line: rgba(93, 76, 224, 0.26);
  --accent-glow: rgba(93, 76, 224, 0.30);

  --green:       #137044;
  --green-soft:  rgba(19, 112, 68, 0.12);
  --green-line:  rgba(19, 112, 68, 0.34);
  --gold:        #946105;
  --gold-soft:   rgba(148, 97, 5, 0.12);
  --gold-line:   rgba(148, 97, 5, 0.30);

  /* On-accent text + theme-aware effects */
  --on-accent:   #ffffff;
  --logo-ink:    #ffffff;
  --heading:     #11141d;
  --card-shadow: 0 18px 40px -24px rgba(29, 34, 48, 0.32);
  --card-shadow-soft: 0 16px 34px -26px rgba(29, 34, 48, 0.28);
  --nav-bg:      rgba(244, 242, 238, 0.72);
  --nav-bg-scrolled: rgba(244, 242, 238, 0.92);
  --nav-bg-mobile: rgba(244, 242, 238, 0.98);
  --eyebrow-bg:  rgba(255, 255, 255, 0.72);
  --grid-opacity: .5;
  --hero-fade:   var(--bg);
  --hero-glow-1: rgba(93, 76, 224, 0.13);
  --hero-glow-2: rgba(10, 125, 111, 0.10);
  --contact-glow: rgba(93, 76, 224, 0.08);
  --card-glow:   rgba(93, 76, 224, 0.10);
  --stat-hover:  rgba(93, 76, 224, 0.05);
  --cat-bg:      rgba(10, 125, 111, 0.09);
  --accent-grad-2: #7d6df0;
}

/* ============================================================
   DARK THEME — original near-black palette, opt-in
   ============================================================ */
:root[data-theme="dark"] {
  /* Surfaces — soft near-black, never pure #000 */
  --bg:          #0a0c12;
  --bg-soft:     #0e1119;
  --bg-card:     #131825;
  --bg-card-solid: #131825;
  --bg-elev:     #1a2031;
  --bg-elev-hi:  #222a3f;

  /* Borders */
  --border:      #20263a;
  --border-soft: #2d3550;
  --border-hi:   #3a4467;

  /* Text hierarchy */
  --text:        #f1f3f9;
  --text-dim:    #a3acc2;
  --text-faint:  #949db4;

  /* One intentional accent (+ supporting hues) */
  --accent:      #7c6cff;
  --accent-hi:   #a497ff;
  --accent-2:    #32e0c8;
  --accent-soft: rgba(124, 108, 255, 0.12);
  --accent-line: rgba(124, 108, 255, 0.22);
  --accent-glow: rgba(124, 108, 255, 0.42);

  --green:       #3ddc97;
  --green-soft:  rgba(61, 220, 151, 0.12);
  --green-line:  rgba(61, 220, 151, 0.32);
  --gold:        #ffd66b;
  --gold-soft:   rgba(255, 214, 107, 0.10);
  --gold-line:   rgba(255, 214, 107, 0.30);

  --on-accent:   #ffffff;
  --logo-ink:    #0a0c12;
  --heading:     #ffffff;
  --card-shadow: 0 30px 56px -28px rgba(0, 0, 0, 0.9);
  --card-shadow-soft: 0 24px 44px -28px rgba(0, 0, 0, 0.85);
  --nav-bg:      rgba(10, 12, 18, 0.55);
  --nav-bg-scrolled: rgba(10, 12, 18, 0.88);
  --nav-bg-mobile: rgba(10, 12, 18, 0.98);
  --eyebrow-bg:  rgba(19, 24, 37, 0.65);
  --grid-opacity: .3;
  --hero-fade:   var(--bg);
  --hero-glow-1: rgba(124, 108, 255, 0.24);
  --hero-glow-2: rgba(50, 224, 200, 0.14);
  --contact-glow: rgba(124, 108, 255, 0.12);
  --card-glow:   rgba(124, 108, 255, 0.14);
  --stat-hover:  rgba(124, 108, 255, 0.05);
  --cat-bg:      rgba(50, 224, 200, 0.06);
  --accent-grad-2: #5c4ce6;
}

/* Smooth cross-fade when switching themes */
body, .nav, .card, .expertise-card, .pill, .btn, .tech-badge, .expertise-chip,
.hero-eyebrow, .hero-stats, .stat, .tag, .card-cat {
  transition-property: background-color, border-color, color, box-shadow;
  transition-duration: .32s;
  transition-timing-function: var(--ease);
}

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

html { scroll-behavior: smooth; scroll-padding-top: 92px; }

body {
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

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

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

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  z-index: 999;
  background: var(--accent);
  color: var(--on-accent);
  padding: 10px 18px;
  border-radius: 0 0 8px 0;
  font-size: 14px;
  font-weight: 600;
}
.skip-link:focus { left: 0; }

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

/* ---------- Scrollbar ---------- */
::-webkit-scrollbar { width: 11px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--border-soft); border-radius: 8px; border: 3px solid var(--bg); }
::-webkit-scrollbar-thumb:hover { background: var(--accent); }

/* ============================================================
   Nav
   ============================================================ */
.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  background: var(--nav-bg);
  backdrop-filter: blur(18px) saturate(150%);
  -webkit-backdrop-filter: blur(18px) saturate(150%);
  border-bottom: 1px solid transparent;
  transition: border-color .3s var(--ease), background .3s var(--ease);
}
.nav.scrolled {
  border-bottom-color: var(--border);
  background: var(--nav-bg-scrolled);
}
.nav-inner {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 14px 32px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.nav-brand { display: flex; align-items: center; gap: 12px; font-weight: 700; }
.nav-logo {
  width: 36px; height: 36px;
  display: grid; place-items: center;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border-radius: 10px;
  font-family: var(--display);
  font-size: 13px; font-weight: 700; color: var(--logo-ink);
  letter-spacing: .5px;
  box-shadow: 0 6px 18px -5px var(--accent-glow);
}
.nav-name { font-size: 15px; letter-spacing: -.2px; }
.nav-links { display: flex; align-items: center; gap: 30px; }
.nav-links a {
  font-size: 14.5px;
  font-weight: 500;
  color: var(--text-dim);
  transition: color .2s var(--ease);
  position: relative;
}
.nav-links a:not(.nav-cta)::after {
  content: "";
  position: absolute;
  left: 0; bottom: -6px;
  width: 100%; height: 2px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  border-radius: 2px;
  transform: scaleX(0);
  transform-origin: left;
  transition: transform .25s var(--ease);
}
.nav-links a:hover { color: var(--text); }
.nav-links a:not(.nav-cta):hover::after,
.nav-links a.current::after { transform: scaleX(1); }
.nav-links a.current { color: var(--text); }
.nav-cta {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  border: 1px solid var(--border-soft);
  border-radius: 10px;
  color: var(--text) !important;
  transition: border-color .2s var(--ease), background .2s var(--ease) !important;
}
.nav-cta:hover { border-color: var(--accent); background: var(--accent-soft); }

/* ---------- Theme toggle ---------- */
.theme-toggle {
  display: inline-grid;
  place-items: center;
  width: 38px; height: 38px;
  flex-shrink: 0;
  border: 1px solid var(--border-soft);
  border-radius: 10px;
  background: var(--bg-card);
  color: var(--text-dim);
  cursor: pointer;
  padding: 0;
  transition: color .2s var(--ease), border-color .2s var(--ease),
              background .2s var(--ease), transform .18s var(--ease);
}
.theme-toggle:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-soft);
  transform: translateY(-1px);
}
.theme-toggle:active { transform: translateY(0); }
.theme-toggle svg { display: block; }
/* Light theme shows the moon (action: go dark); dark shows the sun */
.theme-icon-sun  { display: none; }
.theme-icon-moon { display: block; }
:root[data-theme="dark"] .theme-icon-sun  { display: block; }
:root[data-theme="dark"] .theme-icon-moon { display: none; }

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none; border: none; cursor: pointer; padding: 6px;
}
.nav-toggle span {
  width: 22px; height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: .28s var(--ease);
}
.nav-toggle.is-open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle.is-open span:nth-child(2) { opacity: 0; }
.nav-toggle.is-open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ============================================================
   Hero
   ============================================================ */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 150px 32px 96px;
  overflow: hidden;
}
.hero-bg {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(720px circle at 14% 4%, var(--hero-glow-1), transparent 60%),
    radial-gradient(640px circle at 92% 88%, var(--hero-glow-2), transparent 58%);
  pointer-events: none;
}
.hero-bg::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(var(--border) 1px, transparent 1px),
    linear-gradient(90deg, var(--border) 1px, transparent 1px);
  background-size: 62px 62px;
  opacity: var(--grid-opacity);
  mask-image: radial-gradient(ellipse 74% 64% at 42% 36%, #000 30%, transparent 80%);
  -webkit-mask-image: radial-gradient(ellipse 74% 64% at 42% 36%, #000 30%, transparent 80%);
}
.hero-bg::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg, transparent 58%, var(--bg) 100%);
}
.hero-inner {
  position: relative;
  max-width: var(--maxw);
  margin: 0 auto;
  width: 100%;
}
.hero-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 1.6px;
  text-transform: uppercase;
  color: var(--text-dim);
  padding: 8px 16px;
  border: 1px solid var(--border-soft);
  background: var(--eyebrow-bg);
  border-radius: 100px;
  margin-bottom: 30px;
}
.ping {
  position: relative;
  width: 8px; height: 8px;
  border-radius: 50%;
  background: var(--green);
  flex-shrink: 0;
}
.ping::after {
  content: "";
  position: absolute;
  inset: -4px;
  border-radius: 50%;
  border: 1.5px solid var(--green);
  animation: ping 1.9s var(--ease) infinite;
}
@keyframes ping {
  0%   { transform: scale(.6); opacity: .9; }
  80%, 100% { transform: scale(1.6); opacity: 0; }
}
.hero-title {
  font-family: var(--display);
  font-size: clamp(2.8rem, 7.4vw, 5.7rem);
  font-weight: 600;
  letter-spacing: -2.4px;
  line-height: 1.04;
  color: var(--heading);
}
.hero-title .grad {
  background: linear-gradient(115deg, var(--accent-hi) 8%, var(--accent-2) 92%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hero-subtitle {
  margin-top: 24px;
  font-size: clamp(.95rem, 2vw, 1.2rem);
  font-weight: 600;
  color: var(--accent-hi);
  letter-spacing: -.2px;
}
.hero-bio {
  margin-top: 22px;
  max-width: 690px;
  font-size: 16.5px;
  color: var(--text-dim);
}
.hero-bio strong { color: var(--text); font-weight: 600; }
.hero-actions {
  margin-top: 36px;
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
}

/* ---------- Hero stats strip ---------- */
.hero-stats {
  margin-top: 64px;
  display: grid;
  grid-template-columns: repeat(3, auto) 1fr;
  gap: 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg-card);
  overflow: hidden;
}
.stat {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 24px 32px;
  border-right: 1px solid var(--border);
  transition: background .25s var(--ease);
}
.stat:hover { background: var(--stat-hover); }
.stat:last-child { border-right: none; }
.stat-wide { flex: 1; min-width: 0; }
.stat-num {
  font-family: var(--display);
  font-size: 2.5rem;
  font-weight: 600;
  letter-spacing: -1.2px;
  line-height: 1;
  background: linear-gradient(135deg, var(--accent-hi), var(--accent-2));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.stat-text {
  font-size: 1.02rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -.3px;
  line-height: 1.3;
  margin-bottom: 4px;
}
.stat-label {
  font-size: 12.5px;
  color: var(--text-faint);
  font-weight: 500;
  letter-spacing: .2px;
}
.scroll-cue {
  position: absolute;
  bottom: 30px; left: 50%;
  transform: translateX(-50%);
  width: 26px; height: 42px;
  border: 2px solid var(--border-soft);
  border-radius: 14px;
  display: grid; place-items: start center;
}
.scroll-cue span {
  width: 4px; height: 8px;
  margin-top: 7px;
  background: var(--accent);
  border-radius: 4px;
  animation: scrollPulse 1.7s var(--ease) infinite;
}
@keyframes scrollPulse {
  0%   { opacity: 0; transform: translateY(0); }
  35%  { opacity: 1; }
  70%  { opacity: 0; transform: translateY(13px); }
  100% { opacity: 0; }
}

/* ============================================================
   Buttons
   ============================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  padding: 13px 25px;
  border-radius: 12px;
  font-size: 14.5px;
  font-weight: 600;
  cursor: pointer;
  border: 1px solid transparent;
  font-family: inherit;
  transition: transform .18s var(--ease), box-shadow .25s var(--ease),
              background .25s var(--ease), border-color .25s var(--ease);
}
.btn:active { transform: translateY(1px); }
.btn-primary {
  background: linear-gradient(135deg, var(--accent), var(--accent-grad-2));
  color: var(--on-accent);
  box-shadow: 0 12px 30px -12px var(--accent-glow);
}
.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 18px 42px -12px var(--accent-glow);
}
.btn-ghost {
  background: var(--bg-elev);
  border-color: var(--border-soft);
  color: var(--text);
}
.btn-ghost:hover {
  border-color: var(--accent);
  background: var(--accent-soft);
  transform: translateY(-2px);
}

/* ============================================================
   Sections
   ============================================================ */
.section { padding: 116px 32px; }
.section-inner { max-width: var(--maxw); margin: 0 auto; }
.section-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 2.4px;
  text-transform: uppercase;
  color: var(--accent-2);
  margin-bottom: 16px;
}
.section-eyebrow::before {
  content: "";
  width: 24px; height: 2px;
  background: var(--accent-2);
  border-radius: 2px;
}
.section-title {
  font-family: var(--display);
  font-size: clamp(1.95rem, 4vw, 2.9rem);
  font-weight: 600;
  letter-spacing: -1.4px;
  line-height: 1.12;
  color: var(--heading);
}
.section-lead {
  margin-top: 18px;
  max-width: 680px;
  color: var(--text-dim);
  font-size: 16px;
}
.section-lead strong { color: var(--text); font-weight: 600; }
.section-lead .lead-demo {
  display: inline-flex;
  align-items: center;
  padding: 1px 8px;
  border-radius: 7px;
  background: var(--accent-soft);
  border: 1px solid var(--accent);
  color: var(--accent-hi);
  font-weight: 600;
  font-size: 13px;
  white-space: nowrap;
}

.about { background: var(--bg-soft); border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); }
.about-grid {
  margin-top: 38px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 36px;
}
.about-text {
  color: var(--text-dim);
  font-size: 16.5px;
  position: relative;
  padding-left: 22px;
}
.about-text::before {
  content: "";
  position: absolute;
  left: 0; top: 5px; bottom: 5px;
  width: 2px;
  border-radius: 2px;
  background: linear-gradient(180deg, var(--accent), var(--accent-2));
  opacity: .55;
}
.about-text strong { color: var(--text); font-weight: 600; }

/* ============================================================
   Filters
   ============================================================ */
.filters-row {
  margin: 42px 0 30px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 14px;
}
.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}
.pill {
  padding: 9px 18px;
  border-radius: 100px;
  border: 1px solid var(--border-soft);
  background: var(--bg-card-solid);
  color: var(--text-dim);
  font-family: inherit;
  font-size: 13.5px;
  font-weight: 600;
  cursor: pointer;
  transition: color .2s var(--ease), border-color .2s var(--ease),
              background .2s var(--ease), box-shadow .2s var(--ease);
}
.pill:hover { color: var(--text); border-color: var(--accent); }
.pill.active {
  background: linear-gradient(135deg, var(--accent), var(--accent-grad-2));
  border-color: transparent;
  color: var(--on-accent);
  box-shadow: 0 8px 22px -8px var(--accent-glow);
}
.filter-count {
  font-size: 13px;
  font-weight: 500;
  color: var(--text-faint);
  font-family: var(--mono);
  white-space: nowrap;
}

/* ============================================================
   Project grid — bento-influenced
   ============================================================ */
.grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 22px;
  grid-auto-flow: dense;
}
.card {
  --mx: 50%;
  --my: 0%;
  position: relative;
  grid-column: span 2;
  display: flex;
  flex-direction: column;
  background: var(--bg-card-solid);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 26px 26px 22px;
  overflow: hidden;
  isolation: isolate;
  transition: transform .3s var(--ease), border-color .3s var(--ease),
              box-shadow .3s var(--ease);
}
/* Wide bento tiles — featured public projects */
.card-wide { grid-column: span 3; }

/* Pointer-tracking glow */
.card-glow {
  position: absolute;
  inset: 0;
  z-index: -1;
  border-radius: inherit;
  background: radial-gradient(360px circle at var(--mx) var(--my),
              var(--card-glow), transparent 70%);
  opacity: 0;
  transition: opacity .3s var(--ease);
}
.card:hover .card-glow { opacity: 1; }

/* Top accent line */
.card::before {
  content: "";
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  transform: scaleX(0);
  transform-origin: left;
  transition: transform .4s var(--ease);
  z-index: 1;
}
.card:hover {
  transform: translateY(-6px);
  border-color: var(--border-hi);
  box-shadow: var(--card-shadow);
}
.card:hover::before { transform: scaleX(1); }
.card.hidden { display: none; }

.card-body { display: flex; flex-direction: column; flex-grow: 1; }

/* Featured cards visually distinguished */
.card-featured-state {
  background:
    linear-gradient(180deg, var(--accent-soft), transparent 40%),
    var(--bg-card-solid);
  border-color: var(--border-soft);
}
.card-featured-state::before { transform: scaleX(1); opacity: .5; }
.card-featured-state:hover::before { opacity: 1; }

.card-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 10px;
}
.card-cat {
  font-size: 10.5px;
  font-weight: 700;
  letter-spacing: .8px;
  text-transform: uppercase;
  color: var(--accent-2);
  padding: 4px 11px;
  border: 1px solid var(--accent-line);
  background: var(--cat-bg);
  border-radius: 100px;
  white-space: nowrap;
}
.card-tags {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
  justify-content: flex-end;
}
.tag {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 10px;
  font-weight: 700;
  letter-spacing: .5px;
  text-transform: uppercase;
  padding: 4px 9px;
  border-radius: 100px;
  white-space: nowrap;
  border: 1px solid transparent;
}
.tag svg { flex-shrink: 0; }
.tag-featured {
  color: var(--gold);
  background: var(--gold-soft);
  border-color: var(--gold-line);
}
.tag-public {
  color: var(--green);
  background: var(--green-soft);
  border-color: var(--green-line);
}
.tag-private {
  color: var(--text-faint);
  background: var(--bg-elev-hi);
  border-color: var(--border-soft);
}
.tag-interactive {
  color: var(--accent-hi);
  background: var(--accent-soft);
  border-color: var(--accent);
}
.card-name {
  font-family: var(--display);
  margin-top: 18px;
  font-size: 20px;
  font-weight: 600;
  letter-spacing: -.4px;
  color: var(--heading);
}
.card-wide .card-name { font-size: 24px; }
.card-tagline {
  margin-top: 6px;
  font-size: 13.5px;
  font-weight: 500;
  color: var(--accent-hi);
}
.card-wide .card-tagline { font-size: 15px; }
.card-desc {
  margin-top: 13px;
  font-size: 14px;
  color: var(--text-dim);
  flex-grow: 1;
}
.card-wide .card-desc { font-size: 15px; max-width: 92%; }
.card-tech {
  margin-top: 18px;
  display: flex;
  flex-wrap: wrap;
  gap: 7px;
}
.tech-badge {
  font-size: 11px;
  font-weight: 500;
  font-family: var(--mono);
  color: var(--text-dim);
  background: var(--bg-elev);
  border: 1px solid var(--border);
  padding: 3px 9px;
  border-radius: 6px;
  transition: border-color .2s var(--ease), color .2s var(--ease);
}
.card:hover .tech-badge { border-color: var(--border-soft); }
.card-actions {
  margin-top: 20px;
  padding-top: 18px;
  border-top: 1px solid var(--border);
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
}
.card-btn {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 9px 16px;
  border-radius: 10px;
  font-size: 13px;
  font-weight: 600;
  transition: background .2s var(--ease), color .2s var(--ease),
              border-color .2s var(--ease), transform .18s var(--ease);
}
.card-btn svg { flex-shrink: 0; }
.card-btn-demo {
  background: var(--accent-soft);
  border: 1px solid var(--accent);
  color: var(--accent-hi);
}
.card-btn-demo:hover { background: var(--accent); color: var(--on-accent); transform: translateY(-2px); }
.card-btn-code {
  background: var(--bg-elev);
  border: 1px solid var(--border-soft);
  color: var(--text);
}
.card-btn-code:hover { border-color: var(--text-dim); background: var(--bg-elev-hi); transform: translateY(-2px); }
.card-note {
  font-size: 12.5px;
  font-weight: 500;
  color: var(--text-faint);
  display: inline-flex;
  align-items: center;
  gap: 6px;
}
.card-note svg { opacity: .7; }

/* ============================================================
   What I build (expertise)
   ============================================================ */
.expertise { background: var(--bg-soft); border-top: 1px solid var(--border); }
.expertise-grid {
  margin-top: 42px;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
}
.expertise-card {
  position: relative;
  background: var(--bg-card-solid);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 28px 26px;
  overflow: hidden;
  transition: border-color .25s var(--ease), transform .25s var(--ease),
              box-shadow .25s var(--ease);
}
.expertise-card::before {
  content: "";
  position: absolute;
  left: 0; top: 0; bottom: 0;
  width: 3px;
  background: linear-gradient(180deg, var(--accent), var(--accent-2));
  transform: scaleY(0);
  transform-origin: top;
  transition: transform .35s var(--ease);
}
.expertise-card:hover {
  border-color: var(--border-hi);
  transform: translateY(-4px);
  box-shadow: var(--card-shadow-soft);
}
.expertise-card:hover::before { transform: scaleY(1); }
.expertise-card h3 {
  font-family: var(--display);
  font-size: 18px;
  font-weight: 600;
  letter-spacing: -.3px;
  color: var(--heading);
}
.expertise-blurb {
  margin-top: 8px;
  font-size: 14.5px;
  color: var(--text-dim);
}
.expertise-items {
  margin-top: 18px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.expertise-chip {
  font-size: 12px;
  font-weight: 500;
  font-family: var(--mono);
  color: var(--text);
  background: var(--bg-elev);
  border: 1px solid var(--border-soft);
  padding: 5px 11px;
  border-radius: 7px;
  transition: border-color .2s var(--ease), color .2s var(--ease),
              background .2s var(--ease);
}
.expertise-chip:hover {
  border-color: var(--accent);
  color: var(--accent-hi);
  background: var(--accent-soft);
}

/* ============================================================
   Research
   ============================================================ */
.research { background: var(--bg-soft); border-top: 1px solid var(--border); }
.research-meta {
  margin-top: 28px;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px;
}
.research-link {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  font-size: 13.5px;
  font-weight: 600;
  letter-spacing: -.2px;
  color: var(--on-accent, #fff);
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border: 1px solid var(--accent);
  padding: 9px 16px;
  border-radius: 9px;
  box-shadow: 0 6px 18px -8px var(--accent-glow);
  transition: transform .2s var(--ease), box-shadow .2s var(--ease);
}
.research-link:hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 24px -8px var(--accent-glow);
}
.research-tag {
  font-size: 12px;
  font-weight: 600;
  font-family: var(--mono);
  letter-spacing: .2px;
  color: var(--text-dim);
  background: var(--bg-elev);
  border: 1px solid var(--border-soft);
  padding: 7px 12px;
  border-radius: 100px;
}
.research-list {
  margin-top: 32px;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 18px;
}
.pub-item {
  position: relative;
  background: var(--bg-card-solid);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px 26px 22px;
  overflow: hidden;
  transition: border-color .25s var(--ease), transform .25s var(--ease),
              box-shadow .25s var(--ease);
}
.pub-item::before {
  content: "";
  position: absolute;
  left: 0; top: 0; bottom: 0;
  width: 3px;
  background: linear-gradient(180deg, var(--accent), var(--accent-2));
  transform: scaleY(0);
  transform-origin: top;
  transition: transform .35s var(--ease);
}
.pub-item:hover {
  border-color: var(--border-hi);
  transform: translateY(-4px);
  box-shadow: var(--card-shadow-soft);
}
.pub-item:hover::before { transform: scaleY(1); }
.pub-head {
  display: flex;
  align-items: flex-start;
  gap: 10px;
}
.pub-title {
  font-family: var(--display);
  font-size: 16px;
  font-weight: 600;
  letter-spacing: -.3px;
  line-height: 1.34;
  color: var(--heading);
  flex: 1;
  min-width: 0;
}
.pub-title a { color: inherit; }
.pub-title a:hover { color: var(--accent-hi); }
.pub-badge {
  flex-shrink: 0;
  font-size: 10.5px;
  font-weight: 700;
  letter-spacing: .4px;
  text-transform: uppercase;
  color: var(--accent-hi);
  background: var(--accent-soft);
  border: 1px solid var(--accent-line);
  padding: 4px 9px;
  border-radius: 7px;
  white-space: nowrap;
}
.pub-venue {
  margin-top: 10px;
  font-size: 13px;
  color: var(--text-faint);
  font-weight: 500;
}
.pub-links {
  margin-top: 14px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.pub-links a {
  font-size: 12px;
  font-weight: 600;
  font-family: var(--mono);
  color: var(--text-dim);
  background: var(--bg-elev);
  border: 1px solid var(--border-soft);
  padding: 5px 11px;
  border-radius: 7px;
  transition: border-color .2s var(--ease), color .2s var(--ease),
              background .2s var(--ease);
}
.pub-links a:hover {
  border-color: var(--accent);
  color: var(--accent-hi);
  background: var(--accent-soft);
}
.research-note {
  margin-top: 24px;
  font-size: 14px;
  color: var(--text-faint);
}
.research-note a {
  color: var(--accent-hi);
  font-weight: 600;
  border-bottom: 1px solid var(--accent-line);
}
.research-note a:hover { border-bottom-color: var(--accent); }

/* ============================================================
   Contact
   ============================================================ */
.contact { position: relative; text-align: center; overflow: hidden; }
.contact::before {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(560px circle at 50% 0%, var(--contact-glow), transparent 65%);
  pointer-events: none;
}
.contact .section-inner {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
}
.contact .section-eyebrow { align-self: center; }
.contact .section-lead { margin-left: auto; margin-right: auto; }
.contact-actions {
  margin-top: 32px;
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  justify-content: center;
}

/* ============================================================
   Footer
   ============================================================ */
.footer {
  border-top: 1px solid var(--border);
  background: var(--bg-soft);
  padding: 46px 32px;
}
.footer-inner {
  max-width: var(--maxw);
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
}
.footer-brand { display: flex; flex-direction: column; gap: 3px; }
.footer-name { font-family: var(--display); font-weight: 600; font-size: 15px; }
.footer-role { color: var(--text-faint); font-size: 13px; }
.footer-links { display: flex; gap: 24px; }
.footer-links a {
  font-size: 14px;
  color: var(--text-dim);
  transition: color .2s var(--ease);
}
.footer-links a:hover { color: var(--accent-hi); }
.footer-copy {
  width: 100%;
  font-size: 12.5px;
  color: var(--text-faint);
  border-top: 1px solid var(--border);
  padding-top: 22px;
}

/* ============================================================
   Scroll reveal
   ============================================================ */
.reveal {
  opacity: 0;
  transform: translateY(28px);
  transition: opacity .7s var(--ease), transform .7s var(--ease);
}
.reveal.in { opacity: 1; transform: none; }
.reveal-card {
  opacity: 0;
  transform: translateY(26px) scale(.985);
  transition: opacity .6s var(--ease), transform .6s var(--ease);
}
.reveal-card.in { opacity: 1; transform: none; }

/* ============================================================
   Responsive
   ============================================================ */
@media (max-width: 980px) {
  .grid { grid-template-columns: repeat(4, 1fr); }
  .card { grid-column: span 2; }
  .card-wide { grid-column: span 4; }
  .hero-stats { grid-template-columns: 1fr 1fr; }
  .stat:nth-child(2) { border-right: none; }
  .stat-wide { grid-column: span 2; border-top: 1px solid var(--border); }
}
@media (max-width: 880px) {
  .expertise-grid { grid-template-columns: 1fr; }
  .about-grid { grid-template-columns: 1fr; gap: 22px; }
  .research-list { grid-template-columns: 1fr; }
}
@media (max-width: 720px) {
  .nav-toggle { display: flex; }
  .nav-links {
    position: fixed;
    top: 63px; left: 0; right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background: var(--nav-bg-mobile);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid var(--border);
    padding: 8px 0;
    transform: translateY(-135%);
    transition: transform .34s var(--ease);
  }
  .nav-links.open { transform: translateY(0); }
  .nav-links a { padding: 13px 32px; }
  .nav-links a:not(.nav-cta)::after { display: none; }
  .nav-cta { margin: 8px 32px; justify-content: center; }
  .theme-toggle {
    display: flex;
    align-items: center;
    width: auto;
    height: auto;
    margin: 8px 32px;
    padding: 11px 16px;
    border-radius: 10px;
    justify-content: center;
  }
  .theme-toggle::after {
    content: "Light theme";
    font-size: 14.5px;
    font-weight: 500;
    margin-left: 9px;
  }
  :root[data-theme="dark"] .theme-toggle::after { content: "Dark theme"; }
  .section { padding: 84px 22px; }
  .hero { padding: 128px 22px 84px; }
  .grid { grid-template-columns: 1fr; }
  .card, .card-wide { grid-column: 1 / -1; }
  .card-wide .card-desc { max-width: 100%; }
  .hero-stats { grid-template-columns: 1fr; }
  .stat { border-right: none; border-bottom: 1px solid var(--border); }
  .stat:last-child { border-bottom: none; }
  .stat:nth-child(2) { border-right: none; }
  .stat-wide { grid-column: auto; border-top: none; }
  .filters-row { flex-direction: column; align-items: flex-start; }
  .footer-inner { flex-direction: column; align-items: flex-start; }
}

@media (prefers-reduced-motion: reduce) {
  * { animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; }
  html { scroll-behavior: auto; }
  .reveal, .reveal-card { opacity: 1; transform: none; }
}