/* ===== Variables ===== */
:root {
  --bg: #0a0b0f;
  --bg-card: rgba(18, 20, 28, 0.85);
  --bg-card-hover: rgba(26, 29, 40, 0.95);
  --border: rgba(255, 255, 255, 0.06);
  --border-hover: rgba(255, 255, 255, 0.12);
  --text: #e8e9ec;
  --text-muted: #8b8f9a;
  --accent: #e8b86d;
  --accent-dim: rgba(232, 184, 109, 0.25);
  --accent-glow: rgba(232, 184, 109, 0.15);
  --link: #c9a86c;
  --link-hover: #e8b86d;
  --tag-math: #7eb8da;
  --tag-ml: #b88fd4;
  --tag-bio: #7ed4a0;
  --radius: 14px;
  --radius-sm: 8px;
  --font-serif: "Instrument Serif", Georgia, serif;
  --font-sans: "Outfit", system-ui, sans-serif;
  --space: 1.5rem;
  --header-h: 80px;
}

/* ===== Reset & Base ===== */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 400;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ===== Noise overlay ===== */
.noise {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 100;
  opacity: 0.035;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}

/* ===== Gradient orbs (ambient) ===== */
.gradient-orb {
  position: fixed;
  border-radius: 50%;
  filter: blur(120px);
  opacity: 0.2;
  pointer-events: none;
  z-index: 0;
}
.gradient-orb--1 {
  width: 60vmin;
  height: 60vmin;
  background: var(--accent-dim);
  top: -20%;
  right: -10%;
}
.gradient-orb--2 {
  width: 40vmin;
  height: 40vmin;
  background: rgba(126, 184, 218, 0.2);
  bottom: 10%;
  left: -10%;
}
.gradient-orb--3 {
  width: 35vmin;
  height: 35vmin;
  background: rgba(184, 143, 212, 0.15);
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

/* ===== Layout ===== */
.header, .main, .footer {
  position: relative;
  z-index: 1;
  max-width: 900px;
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--space);
  padding-right: var(--space);
}

/* ===== Header ===== */
.header {
  padding-top: calc(var(--header-h) + 1rem);
  padding-bottom: 3rem;
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-muted);
  text-decoration: none;
  margin-bottom: 2rem;
  transition: color 0.2s ease;
}
.back-link:hover { color: var(--accent); }

.hero-title {
  font-family: var(--font-serif);
  font-size: clamp(2.5rem, 8vw, 4rem);
  font-weight: 400;
  line-height: 1.1;
  margin: 0 0 0.5rem;
  letter-spacing: -0.02em;
}
.hero-title__line { display: block; }
.hero-title__line--accent { color: var(--accent); }

.hero-subtitle {
  margin: 0;
  font-size: 1.1rem;
  color: var(--text-muted);
  font-weight: 400;
}

/* ===== Controls ===== */
.controls {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space);
  align-items: center;
  margin-bottom: 2.5rem;
}

.search-wrap {
  position: relative;
  flex: 1;
  min-width: 200px;
}
.search-icon {
  position: absolute;
  left: 1rem;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1.1rem;
  color: var(--text-muted);
  pointer-events: none;
}
.search-input {
  width: 100%;
  padding: 0.75rem 1rem 0.75rem 2.75rem;
  font-family: var(--font-sans);
  font-size: 0.95rem;
  color: var(--text);
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}
.search-input::placeholder { color: var(--text-muted); }
.search-input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-glow);
}

.filter-wrap {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
}
.filter-label {
  font-size: 0.85rem;
  color: var(--text-muted);
  font-weight: 500;
}
.filter-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}
.chip {
  padding: 0.4rem 0.85rem;
  font-family: var(--font-sans);
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-muted);
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 999px;
  cursor: pointer;
  transition: color 0.2s ease, border-color 0.2s ease, background 0.2s ease;
}
.chip:hover {
  color: var(--text);
  border-color: var(--border-hover);
  background: var(--bg-card);
}
.chip--active {
  color: var(--bg);
  background: var(--accent);
  border-color: var(--accent);
}

/* ===== Sections ===== */
.section {
  margin-bottom: 3rem;
}
.section-title {
  font-family: var(--font-serif);
  font-size: 1.5rem;
  font-weight: 400;
  margin: 0 0 1.25rem;
  display: flex;
  align-items: baseline;
  gap: 0.5rem;
}
.section-title__count {
  font-family: var(--font-sans);
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-muted);
}

.card-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

/* ===== Cards ===== */
.pub-card {
  --tilt-x: 0deg;
  --tilt-y: 0deg;
  position: relative;
  display: block;
  padding: 1.5rem 1.75rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  color: inherit;
  transition: border-color 0.25s ease, background 0.25s ease, box-shadow 0.25s ease, transform 0.2s ease;
  transform: perspective(800px) rotateX(var(--tilt-x)) rotateY(var(--tilt-y));
}
.pub-card:hover {
  border-color: var(--border-hover);
  background: var(--bg-card-hover);
  box-shadow: 0 12px 40px -12px rgba(0, 0, 0, 0.5), 0 0 0 1px var(--accent-glow);
}
.pub-card:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.pub-card__badge {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  padding: 0.25rem 0.6rem;
  border-radius: var(--radius-sm);
  margin-bottom: 0.75rem;
}
.pub-card__badge--published { background: var(--tag-bio); color: #0a0b0f; }
.pub-card__badge--in-progress { background: var(--tag-ml); color: #0a0b0f; }
.pub-card__badge--poster { background: var(--accent); color: #0a0b0f; }

.pub-card__title {
  font-family: var(--font-serif);
  font-size: 1.25rem;
  font-weight: 400;
  line-height: 1.35;
  margin: 0 0 0.5rem;
  color: var(--text);
}
.pub-card:hover .pub-card__title { color: var(--accent); }

.pub-card__meta {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 0.6rem;
}

.pub-card__desc {
  font-size: 0.9rem;
  color: var(--text-muted);
  line-height: 1.55;
  margin: 0 0 1rem;
}

.pub-card__tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}
.pub-card__tag {
  font-size: 0.75rem;
  font-weight: 500;
  padding: 0.2rem 0.5rem;
  border-radius: 4px;
  background: rgba(255, 255, 255, 0.06);
  color: var(--text-muted);
}
.pub-card__tag--math { background: rgba(126, 184, 218, 0.15); color: var(--tag-math); }
.pub-card__tag--ml { background: rgba(184, 143, 212, 0.15); color: var(--tag-ml); }
.pub-card__tag--bio { background: rgba(126, 212, 160, 0.12); color: var(--tag-bio); }

.pub-card__links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 0.75rem;
}
.pub-card__link {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--bg);
  background: rgba(232, 184, 109, 0.9);
  border: 1px solid rgba(232, 184, 109, 0.55);
  border-radius: 999px;
  padding: 0.35rem 0.75rem;
  text-decoration: none;
  transition: transform 0.2s ease, opacity 0.2s ease;
}
.pub-card__link:hover {
  opacity: 0.95;
  transform: translateY(-1px);
}

/* Card enter animation */
.pub-card.animate-in {
  animation: cardIn 0.55s ease forwards;
}
@keyframes cardIn {
  from {
    opacity: 0;
    transform: translateY(24px) perspective(800px) rotateX(0) rotateY(0);
  }
  to {
    opacity: 1;
    transform: translateY(0) perspective(800px) rotateX(var(--tilt-x)) rotateY(var(--tilt-y));
  }
}

/* ===== Empty state ===== */
.empty-state {
  text-align: center;
  padding: 3rem var(--space);
  color: var(--text-muted);
}
.empty-state.hidden { display: none; }
.btn-reset {
  margin-top: 1rem;
  padding: 0.5rem 1rem;
  font-family: var(--font-sans);
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--accent);
  background: transparent;
  border: 1px solid var(--accent);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background 0.2s ease, color 0.2s ease;
}
.btn-reset:hover {
  background: var(--accent);
  color: var(--bg);
}

/* ===== Footer ===== */
.footer {
  padding: 2rem var(--space) 3rem;
  border-top: 1px solid var(--border);
}
.footer__text {
  margin: 0;
  font-size: 0.9rem;
  color: var(--text-muted);
}
.footer__text a {
  color: var(--link);
  text-decoration: none;
  transition: color 0.2s ease;
}
.footer__text a:hover { color: var(--link-hover); }
.footer__dot { margin: 0 0.5rem; }

/* ===== Reduced motion ===== */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; transition-duration: 0.01ms !important; }
  .pub-card { transform: none; }
}