/* =============================================================
   Samuel Alipour-fard — personal site
   Design system: modern dark, physics accent (violet → cyan)
   Hand-authored, no build step. Works on GitHub Pages.
   ============================================================= */

/* ---------- Design tokens ---------- */
:root {
  /* Dark theme (default) */
  --bg:            #0a0b10;
  --bg-grid:       rgba(255, 255, 255, 0.025);
  --surface:       #0e1017;
  --card:          #12141d;
  --card-hover:    #171a26;
  --border:        rgba(255, 255, 255, 0.08);
  --border-strong: rgba(255, 255, 255, 0.16);

  --text:      #eef0f6;
  --text-mid:  #b4b9ca;
  --text-dim:  #7b8194;

  --accent:    #8b9dff;   /* indigo */
  --accent-2:  #56d9e0;   /* cyan   */
  --accent-3:  #c08bff;   /* violet */
  --accent-ink:#0a0b10;   /* text on accent */
  --grad:      linear-gradient(120deg, var(--accent-3) 0%, var(--accent) 45%, var(--accent-2) 100%);
  --glow:      radial-gradient(60% 60% at 50% 0%, rgba(139,157,255,0.16) 0%, rgba(86,217,224,0.06) 40%, transparent 72%);

  --shadow-sm: 0 1px 2px rgba(0,0,0,0.4);
  --shadow-md: 0 8px 30px rgba(0,0,0,0.35);
  --shadow-lg: 0 24px 60px -20px rgba(0,0,0,0.6);
  --ring:      0 0 0 1px var(--border-strong);

  --font-display: "Fraunces", "Iowan Old Style", Georgia, "Times New Roman", serif;
  --font-body:    "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono:    "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  --maxw: 1120px;
  --radius:    16px;
  --radius-sm: 10px;
  --radius-lg: 24px;

  --nav-h: 66px;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
}

html[data-theme="light"] {
  --bg:            #f6f7fb;
  --bg-grid:       rgba(10, 15, 40, 0.035);
  --surface:       #eef0f6;
  --card:          #ffffff;
  --card-hover:    #ffffff;
  --border:        rgba(12, 16, 30, 0.10);
  --border-strong: rgba(12, 16, 30, 0.20);

  --text:     #14161f;
  --text-mid: #414762;
  --text-dim: #6b7189;

  --accent:   #5a5fe0;
  --accent-2: #0d9aa6;
  --accent-3: #8b41d8;
  --accent-ink: #ffffff;
  --glow:     radial-gradient(60% 60% at 50% 0%, rgba(90,95,224,0.12) 0%, rgba(13,154,166,0.05) 40%, transparent 72%);

  --shadow-md: 0 10px 30px rgba(20,30,70,0.10);
  --shadow-lg: 0 30px 60px -25px rgba(20,30,70,0.22);
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 84px;
  -webkit-text-size-adjust: 100%;
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }
}

body {
  margin: 0;
  background-color: var(--bg);
  background-image:
    linear-gradient(var(--bg-grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--bg-grid) 1px, transparent 1px);
  background-size: 46px 46px;
  color: var(--text);
  font-family: var(--font-body);
  font-size: 17px;
  line-height: 1.65;
  letter-spacing: 0.005em;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

a { color: var(--accent-2); text-decoration: none; transition: color 0.2s var(--ease); }
a:hover { color: var(--accent); }

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

h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 600;
  line-height: 1.1;
  letter-spacing: -0.02em;
  margin: 0;
  color: var(--text);
}

::selection { background: rgba(139,157,255,0.28); color: #fff; }

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

/* ---------- Layout helpers ---------- */
.wrap { width: 100%; max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }

.section { padding: 96px 0; position: relative; }
.section--tight { padding: 64px 0; }

.eyebrow {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--accent-2);
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 18px;
}
.eyebrow::before {
  content: "";
  width: 26px; height: 1px;
  background: linear-gradient(90deg, var(--accent-2), transparent);
}

.section-title {
  font-size: clamp(1.9rem, 4vw, 2.8rem);
  max-width: 20ch;
}
.section-lead {
  color: var(--text-mid);
  max-width: 60ch;
  margin-top: 16px;
  font-size: 1.06rem;
}

.section-head { margin-bottom: 52px; }

.grad-text {
  background: var(--grad);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  font-family: var(--font-body);
  font-weight: 550;
  font-size: 0.96rem;
  padding: 12px 22px;
  border-radius: 999px;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform 0.2s var(--ease), background 0.2s var(--ease), border-color 0.2s var(--ease), color 0.2s var(--ease);
  white-space: nowrap;
}
.btn svg { width: 17px; height: 17px; }
.btn-primary {
  background: var(--grad);
  color: var(--accent-ink);
  font-weight: 600;
}
.btn-primary:hover { transform: translateY(-2px); color: var(--accent-ink); }
.btn-ghost {
  background: transparent;
  color: var(--text);
  border-color: var(--border-strong);
}
.btn-ghost:hover { border-color: var(--accent); color: var(--text); background: rgba(139,157,255,0.06); transform: translateY(-2px); }

/* ---------- Navigation ---------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--nav-h);
  display: flex;
  align-items: center;
  border-bottom: 1px solid transparent;
  transition: background 0.3s var(--ease), border-color 0.3s var(--ease), backdrop-filter 0.3s var(--ease);
}
.nav.scrolled {
  background: color-mix(in srgb, var(--bg) 72%, transparent);
  backdrop-filter: blur(14px) saturate(140%);
  -webkit-backdrop-filter: blur(14px) saturate(140%);
  border-bottom-color: var(--border);
}
.nav .wrap { display: flex; align-items: center; justify-content: space-between; gap: 16px; }

.brand { display: flex; align-items: center; gap: 11px; font-family: var(--font-display); font-weight: 600; font-size: 1.06rem; color: var(--text); letter-spacing: -0.01em; }
.brand:hover { color: var(--text); }
.brand .mark { width: 30px; height: 30px; flex: none; }
.brand-short { display: none; }  /* mobile-only short name; desktop shows the full name */

.nav-links { display: flex; align-items: center; gap: 6px; list-style: none; margin: 0; padding: 0; }
.nav-links a {
  color: var(--text-mid);
  font-size: 0.93rem;
  font-weight: 500;
  padding: 8px 13px;
  border-radius: 8px;
  transition: color 0.2s, background 0.2s;
}
.nav-links a:hover { color: var(--text); background: var(--card); }
.nav-links a.active { color: var(--text); }

.nav-right { display: flex; align-items: center; gap: 10px; }

.theme-toggle {
  width: 38px; height: 38px;
  display: inline-flex; align-items: center; justify-content: center;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--text-mid);
  cursor: pointer;
  transition: color 0.2s, border-color 0.2s, transform 0.2s;
}
.theme-toggle:hover { color: var(--text); border-color: var(--border-strong); transform: translateY(-1px); }
.theme-toggle svg { width: 18px; height: 18px; }
html[data-theme="light"] .theme-toggle .icon-sun { display: none; }
html[data-theme="light"] .theme-toggle .icon-moon { display: block; }
.theme-toggle .icon-sun { display: block; }
.theme-toggle .icon-moon { display: none; }

.nav-toggle { display: none; }

/* ---------- Hero ---------- */
.hero {
  position: relative;
  padding: clamp(70px, 12vh, 130px) 0 84px;
  overflow: hidden;
}
.hero::before {
  content: "";
  position: absolute;
  inset: -20% 0 auto 0;
  height: 720px;
  background: var(--glow);
  pointer-events: none;
  z-index: 0;
}
.hero .wrap { position: relative; z-index: 1; }

.hero-grid {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 56px;
  align-items: center;
}

.hero-status {
  display: inline-flex; align-items: center; gap: 9px;
  font-family: var(--font-mono); font-size: 0.78rem; letter-spacing: 0.08em;
  color: var(--text-mid);
  background: var(--card);
  border: 1px solid var(--border);
  padding: 7px 14px;
  border-radius: 999px;
  margin-bottom: 26px;
}
.hero-status .dot { width: 8px; height: 8px; border-radius: 50%; background: var(--accent-2); box-shadow: 0 0 0 0 rgba(86,217,224,0.6); animation: pulse 2.4s infinite; }
@keyframes pulse {
  0%   { box-shadow: 0 0 0 0 rgba(86,217,224,0.5); }
  70%  { box-shadow: 0 0 0 8px rgba(86,217,224,0); }
  100% { box-shadow: 0 0 0 0 rgba(86,217,224,0); }
}

.hero h1 {
  font-size: clamp(2.7rem, 6.4vw, 4.6rem);
  line-height: 0.98;
  margin-bottom: 8px;
}
.hero .subtitle {
  font-family: var(--font-mono);
  font-size: clamp(0.92rem, 1.6vw, 1.06rem);
  letter-spacing: 0.06em;
  color: var(--text-mid);
  margin: 14px 0 26px;
}
.hero .subtitle .sep { color: var(--accent); margin: 0 8px; }
.hero-lead {
  font-size: 1.16rem;
  color: var(--text-mid);
  max-width: 46ch;
  margin-bottom: 30px;
}
.hero-lead strong { color: var(--text); font-weight: 600; }

.hero-cta { display: flex; flex-wrap: wrap; gap: 14px; margin-bottom: 30px; }

.tag-strip { display: flex; flex-wrap: wrap; gap: 10px; }
.tag {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  letter-spacing: 0.06em;
  color: var(--text-mid);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 6px 13px;
  background: color-mix(in srgb, var(--card) 60%, transparent);
}

/* Hero visual — animated correlator bullseye */
.hero-visual {
  position: relative;
  aspect-ratio: 1 / 1;
  display: grid;
  place-items: center;
}
.hero-visual .orb {
  position: absolute;
  inset: 8%;
  border-radius: 50%;
  background: var(--glow);
  filter: blur(6px);
}
.hero-visual svg { width: 100%; height: 100%; position: relative; }

/* stats row under hero */
.stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 14px;
  margin-top: 68px;
  border-top: 1px solid var(--border);
  padding-top: 34px;
}
.stat .num {
  font-family: var(--font-display);
  font-size: clamp(1.7rem, 3vw, 2.4rem);
  font-weight: 600;
  line-height: 1;
}
.stat .lbl { color: var(--text-dim); font-size: 0.86rem; margin-top: 8px; }

/* ---------- Featured projects ---------- */
.feature {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 44px;
  align-items: center;
  padding: 40px 0;
}
.feature + .feature { border-top: 1px solid var(--border); }
.feature.reverse .feature-media { order: 2; }

.feature-media {
  position: relative;
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--border);
  background: var(--surface);
  box-shadow: var(--shadow-lg);
}
.feature-media::after {
  content: ""; position: absolute; inset: 0;
  box-shadow: inset 0 0 0 1px var(--border);
  border-radius: inherit; pointer-events: none;
}
.feature-media img, .feature-media video { width: 100%; height: 100%; object-fit: cover; display: block; }
.feature-media.pad { padding: 22px; background: radial-gradient(120% 120% at 50% 0%, var(--card-hover), var(--surface)); }
.feature-media.pad img { border-radius: 12px; object-fit: contain; }

.feature-badge {
  position: absolute; top: 16px; left: 16px; z-index: 2;
  font-family: var(--font-mono); font-size: 0.72rem; letter-spacing: 0.1em; text-transform: uppercase;
  background: rgba(10,11,16,0.7); backdrop-filter: blur(6px);
  color: var(--accent-2); border: 1px solid var(--border-strong);
  padding: 6px 12px; border-radius: 999px;
}

.feature-body .kicker {
  font-family: var(--font-mono); font-size: 0.76rem; letter-spacing: 0.18em; text-transform: uppercase;
  color: var(--accent-2); margin-bottom: 14px;
}
.feature-body h3 { font-size: clamp(1.5rem, 3vw, 2rem); margin-bottom: 14px; }
.feature-body p { color: var(--text-mid); margin: 0 0 18px; }
.feature-meta { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 22px; }
.chip {
  font-family: var(--font-mono); font-size: 0.72rem; letter-spacing: 0.04em;
  color: var(--text-mid); background: var(--card); border: 1px solid var(--border);
  padding: 5px 11px; border-radius: 7px;
}
.chip.accent { color: var(--accent-2); border-color: color-mix(in srgb, var(--accent-2) 40%, var(--border)); }
.feature-links { display: flex; flex-wrap: wrap; gap: 18px; align-items: center; }
.link-arrow { display: inline-flex; align-items: center; gap: 6px; font-weight: 550; font-size: 0.95rem; }
.link-arrow svg { width: 15px; height: 15px; transition: transform 0.2s var(--ease); }
.link-arrow:hover svg { transform: translate(3px, -3px); }

/* ---------- Card grid (projects / notes) ---------- */
.grid { display: grid; gap: 22px; }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-2 { grid-template-columns: repeat(2, 1fr); }

.card {
  position: relative;
  display: flex;
  flex-direction: column;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  transition: transform 0.3s var(--ease), border-color 0.3s var(--ease), box-shadow 0.3s var(--ease);
}
.card:hover { transform: translateY(-4px); border-color: var(--border-strong); box-shadow: var(--shadow-md); }

.card-thumb {
  aspect-ratio: 16 / 10;
  background: radial-gradient(130% 130% at 50% 0%, var(--card-hover), var(--surface));
  border-bottom: 1px solid var(--border);
  display: grid; place-items: center;
  overflow: hidden;
}
.card-thumb img { width: 100%; height: 100%; object-fit: cover; }
.card-thumb.contain { padding: 18px; }
.card-thumb.contain img { object-fit: contain; }

/* generative thumbnail (no screenshot) */
.card-thumb.gen { position: relative; }
.card-thumb.gen .glyph {
  font-family: var(--font-mono); font-size: 2.2rem; font-weight: 700;
  color: var(--accent); opacity: 0.9; letter-spacing: -0.03em;
}
.card-thumb.gen::before {
  content: ""; position: absolute; inset: 0;
  background:
    radial-gradient(40% 60% at 18% 12%, color-mix(in srgb, var(--accent-3) 22%, transparent), transparent 60%),
    radial-gradient(50% 60% at 88% 90%, color-mix(in srgb, var(--accent-2) 20%, transparent), transparent 60%);
}

.card-body { padding: 22px 22px 20px; display: flex; flex-direction: column; flex: 1; }
.card-lang {
  display: inline-flex; align-items: center; gap: 7px;
  font-family: var(--font-mono); font-size: 0.74rem; color: var(--text-dim);
  margin-bottom: 12px;
}
.card-lang .lang-dot { width: 9px; height: 9px; border-radius: 50%; }
.card h3 { font-size: 1.22rem; margin-bottom: 9px; }
.card h3 a { color: var(--text); }
.card h3 a:hover { color: var(--accent); }
.card p { color: var(--text-mid); font-size: 0.95rem; margin: 0 0 18px; flex: 1; }
.card-foot { display: flex; align-items: center; gap: 16px; flex-wrap: wrap; }
.card-foot a { display: inline-flex; align-items: center; gap: 6px; font-size: 0.86rem; font-weight: 550; color: var(--text-mid); }
.card-foot a:hover { color: var(--accent); }
.card-foot svg { width: 15px; height: 15px; }
.card-foot .stars { margin-left: auto; color: var(--text-dim); font-family: var(--font-mono); font-size: 0.78rem; }

/* language dot colors */
.lang-Python { background: #4b8bbe; }
.lang-Mathematica { background: #dd1100; }
.lang-Cpp { background: #f34b7d; }
.lang-Fortran { background: #734f96; }
.lang-TeX { background: #3d6117; }
.lang-Jupyter { background: #da5b0b; }
.lang-HTML { background: #e34c26; }

/* filter pills (projects page) */
.filters { display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: 36px; }
.filter {
  font-family: var(--font-mono); font-size: 0.8rem; letter-spacing: 0.03em;
  color: var(--text-mid); background: var(--card); border: 1px solid var(--border);
  padding: 8px 15px; border-radius: 999px; cursor: pointer; transition: all 0.2s var(--ease);
}
.filter:hover { color: var(--text); border-color: var(--border-strong); }
.filter.active { color: var(--accent-ink); background: var(--grad); border-color: transparent; font-weight: 600; }

/* ---------- About ---------- */
.about-grid { display: grid; grid-template-columns: 1.35fr 1fr; gap: 56px; align-items: start; }
.about-body p { color: var(--text-mid); margin: 0 0 20px; font-size: 1.06rem; }
.about-body strong { color: var(--text); }

.timeline { list-style: none; margin: 0; padding: 0; }
.timeline li { position: relative; padding: 0 0 26px 26px; border-left: 1px solid var(--border); }
.timeline li:last-child { padding-bottom: 0; }
.timeline li::before {
  content: ""; position: absolute; left: -5px; top: 5px;
  width: 9px; height: 9px; border-radius: 50%; background: var(--accent);
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--accent) 18%, transparent);
}
.timeline .yr { font-family: var(--font-mono); font-size: 0.76rem; color: var(--accent-2); letter-spacing: 0.06em; }
.timeline .role { color: var(--text); font-weight: 600; margin-top: 3px; }
.timeline .place { color: var(--text-dim); font-size: 0.92rem; }
.timeline .sub { list-style: none; margin: 13px 0 2px; padding: 0; display: grid; gap: 8px; }
.timeline .sub li { display: flex; gap: 12px; align-items: baseline; font-size: 0.92rem; color: var(--text-mid); }
.timeline .sub .sy { font-family: var(--font-mono); font-size: 0.72rem; color: var(--accent-2); flex: none; min-width: 66px; letter-spacing: 0.03em; }
.timeline .sub .t2 { font-family: var(--font-mono); font-size: 0.62rem; letter-spacing: 0.04em; text-transform: uppercase; color: var(--text-dim); border: 1px solid var(--border); border-radius: 5px; padding: 1px 6px; margin-left: 6px; white-space: nowrap; }
.timeline .sub em { color: var(--text); font-style: italic; }

/* ---------- Skills ---------- */
.skills-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 22px; }
.skill-card { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); padding: 26px; }
.skill-card h4 { font-family: var(--font-body); font-weight: 600; font-size: 0.82rem; letter-spacing: 0.14em; text-transform: uppercase; color: var(--accent-2); margin-bottom: 16px; }
.skill-tags { display: flex; flex-wrap: wrap; gap: 9px; }
.skill-tags span {
  font-size: 0.9rem; color: var(--text-mid);
  background: var(--surface); border: 1px solid var(--border);
  padding: 6px 12px; border-radius: 8px;
}

/* ---------- Publications ---------- */
.pub-list { list-style: none; margin: 0; padding: 0; }
.pub {
  display: grid;
  grid-template-columns: 92px 1fr;
  gap: 24px;
  padding: 26px 0;
  border-top: 1px solid var(--border);
}
.pub:first-child { border-top: none; }
.pub .pub-year { font-family: var(--font-mono); font-size: 0.92rem; color: var(--accent-2); padding-top: 3px; }
.pub .pub-venue-tag {
  display: inline-block; margin-top: 8px;
  font-family: var(--font-mono); font-size: 0.68rem; letter-spacing: 0.06em;
  color: var(--text-dim); border: 1px solid var(--border); border-radius: 6px; padding: 3px 8px;
}
.pub h3 { font-size: 1.18rem; line-height: 1.3; margin-bottom: 8px; }
.pub h3 a { color: var(--text); }
.pub h3 a:hover { color: var(--accent); }
.pub .authors { color: var(--text-mid); font-size: 0.95rem; margin-bottom: 4px; }
.pub .authors .me { color: var(--text); font-weight: 600; }
.pub .venue { color: var(--text-dim); font-size: 0.92rem; font-style: italic; }
.pub-links { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 14px; }
.pub-links a {
  font-family: var(--font-mono); font-size: 0.76rem; letter-spacing: 0.02em;
  color: var(--text-mid); border: 1px solid var(--border); border-radius: 7px; padding: 5px 11px;
  transition: all 0.2s var(--ease);
}
.pub-links a:hover { color: var(--accent-2); border-color: color-mix(in srgb, var(--accent-2) 45%, var(--border)); }
.pill-featured { color: var(--accent-3) !important; border-color: color-mix(in srgb, var(--accent-3) 45%, var(--border)) !important; }

/* ---------- Talks / simple list ---------- */
.rows { list-style: none; margin: 0; padding: 0; }
.row {
  display: grid; grid-template-columns: 140px 1fr; gap: 22px;
  padding: 22px 0; border-top: 1px solid var(--border);
}
.row:first-child { border-top: none; }
.row .row-when { font-family: var(--font-mono); font-size: 0.82rem; color: var(--text-dim); }
.row h3 { font-size: 1.08rem; margin-bottom: 6px; }
.row p { color: var(--text-mid); font-size: 0.95rem; margin: 0; }

/* ---------- Contact ---------- */
.contact { text-align: center; }
.contact .section-title { margin: 0 auto; max-width: 22ch; }
.contact-lead { margin: 18px auto 34px; }
.social-row { display: flex; justify-content: center; flex-wrap: wrap; gap: 14px; }
.social {
  display: inline-flex; align-items: center; gap: 9px;
  padding: 12px 20px; border-radius: 12px;
  background: var(--card); border: 1px solid var(--border); color: var(--text-mid);
  font-weight: 500; font-size: 0.95rem;
  transition: all 0.2s var(--ease);
}
.social:hover { color: var(--text); border-color: var(--border-strong); transform: translateY(-3px); background: var(--card-hover); }
.social svg { width: 18px; height: 18px; }

/* ---------- Footer ---------- */
.footer { border-top: 1px solid var(--border); padding: 40px 0; margin-top: 40px; }
.footer .wrap { display: flex; align-items: center; justify-content: space-between; gap: 20px; flex-wrap: wrap; }
.footer p { color: var(--text-dim); font-size: 0.88rem; margin: 0; }
.footer .foot-links { display: flex; gap: 20px; }
.footer .foot-links a { color: var(--text-dim); font-size: 0.88rem; }
.footer .foot-links a:hover { color: var(--accent); }

/* ---------- Page header (sub-pages) ---------- */
.page-head { padding: calc(var(--nav-h) - 20px) 0 20px; position: relative; overflow: hidden; }
.page-head::before { content: ""; position: absolute; inset: -40% 0 auto 0; height: 480px; background: var(--glow); z-index: 0; }
.page-head .wrap { position: relative; z-index: 1; }
.page-head h1 { font-size: clamp(2.2rem, 5vw, 3.4rem); margin: 14px 0 0; }
.page-head p { color: var(--text-mid); max-width: 60ch; margin: 16px 0 0; font-size: 1.08rem; }
.crumb { display: inline-flex; align-items: center; gap: 8px; color: var(--text-dim); font-size: 0.9rem; }
.crumb a { color: var(--text-dim); }
.crumb a:hover { color: var(--accent); }

/* ---------- Hero visual animation ---------- */
.spin { transform-origin: 50% 50%; animation: spin 46s linear infinite; }
.spin-rev { transform-origin: 50% 50%; animation: spin 34s linear infinite reverse; }
@keyframes spin { to { transform: rotate(360deg); } }
.orbit-dot { animation: orbit-fade 4s ease-in-out infinite; }
@keyframes orbit-fade { 0%, 100% { opacity: 0.4; } 50% { opacity: 1; } }

/* QCD hero: three colour-charged quarks pulled to the centre by gluon "springs",
   the whole bound state rotating and gently breathing (spring pull). */
.qcd-breathe { transform-box: view-box; transform-origin: 200px 200px; animation: qcd-breathe 8s ease-in-out infinite; }
.qcd-spin    { transform-box: view-box; transform-origin: 200px 200px; animation: spin 8s linear infinite; }
/* quarks swing from +R through the centre to -R and back (springs stay anchored at centre) */
@keyframes qcd-breathe { 0%, 100% { transform: scale(1); } 50% { transform: scale(-1); } }
.gluon-spring { fill: none; stroke: var(--text-mid); stroke-width: 2; stroke-linecap: round; opacity: 0.5; }
.quark-core   { fill: var(--text); opacity: 0.85; }

/* ---------- Reveal-on-scroll (only when JS is present, so no-JS users see everything) ---------- */
.js .reveal { opacity: 0; transform: translateY(22px); transition: opacity 0.7s var(--ease), transform 0.7s var(--ease); }
.js .reveal.in { opacity: 1; transform: none; }

/* ---------- Responsive ---------- */
@media (max-width: 940px) {
  .hero-grid { grid-template-columns: 1fr; gap: 40px; }
  .hero-visual { max-width: 420px; margin: 0 auto; }
  .about-grid { grid-template-columns: 1fr; gap: 40px; }
  .feature, .feature.reverse { grid-template-columns: 1fr; gap: 26px; }
  .feature.reverse .feature-media { order: 0; }
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 720px) {
  body { font-size: 16px; }
  .section { padding: 68px 0; }
  .nav-links { display: none; }
  .nav-toggle {
    display: inline-flex; align-items: center; justify-content: center;
    width: 38px; height: 38px; border-radius: 10px;
    border: 1px solid var(--border); background: var(--card); color: var(--text); cursor: pointer;
  }
  .nav-toggle svg { width: 20px; height: 20px; }
  .nav-links.open {
    display: flex; flex-direction: column; align-items: stretch;
    position: absolute; top: var(--nav-h); left: 0; right: 0;
    background: var(--surface); border-bottom: 1px solid var(--border);
    padding: 12px 24px 18px; gap: 2px;
  }
  .nav-links.open a { padding: 12px 10px; }
  .stats { grid-template-columns: repeat(2, 1fr); gap: 24px 14px; }
  .grid-3, .grid-2 { grid-template-columns: 1fr; }
  .skills-grid { grid-template-columns: 1fr; }
  .pub { grid-template-columns: 1fr; gap: 6px; }
  .pub .pub-year { padding-top: 0; }
  .row { grid-template-columns: 1fr; gap: 6px; }
  .hero .subtitle .sep.mobile-break { display: block; height: 0; }
}

/* ---------- Mobile: keep everything within the viewport (no horizontal scroll) ---------- */
@media (max-width: 720px) {
  /* clip stray horizontal overflow without breaking the sticky nav (clip keeps overflow-y visible) */
  html, body { overflow-x: clip; }
  /* let long unbreakable tokens (repo names, DOIs, long titles) wrap instead of spilling over */
  h1, h2, h3, h4, p, li, a, span, em, strong, div { overflow-wrap: anywhere; }
  .wrap { padding: 0 18px; }

  /* name stays on its two lines and never overflows */
  .hero h1 { font-size: clamp(1.9rem, 9vw, 2.6rem); line-height: 1.03; }

  /* compact the nav so the brand + controls fit on narrow screens */
  .brand span { font-size: clamp(0.82rem, 3.6vw, 1.06rem); }
  .brand .mark { width: 26px; height: 26px; }
  .brand-full { display: none; }
  .brand-short { display: inline; }
  .nav-right { gap: 8px; }
  .nav-right .btn-ghost { padding: 9px 13px; font-size: 0.88rem; }
  .theme-toggle, .nav-toggle { width: 34px; height: 34px; }

  /* trajectory sub-items wrap cleanly instead of running past the edge */
  .timeline .sub li { flex-wrap: wrap; }
  .timeline .sub .sy { min-width: 46px; }
}