/* Researcher's Guide to Physical AI — public site
   Palette taken from the cover art: near-black navy, brushed steel, cyan glow. */

:root {
  --bg:        #080c12;
  --bg-raised: #0e141d;
  --bg-hover:  #131b26;
  --border:    #1e2836;
  --border-lit:#2c3a4d;
  --text:      #e8edf4;
  --text-dim:  #9aa8bb;
  --text-mute: #6b7a8f;
  --accent:    #22d3ee;
  --accent-dim:#0e7f92;
  --accent-glow: rgba(34, 211, 238, .14);

  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto,
          "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;

  --wrap: 1080px;
  --radius: 14px;
}

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

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  /* Soft cyan bloom behind the top of the page, echoing the cover */
  background-image:
    radial-gradient(900px 420px at 50% -180px, rgba(34, 211, 238, .10), transparent 70%);
  background-repeat: no-repeat;
}

.wrap { width: min(100% - 2.5rem, var(--wrap)); margin-inline: auto; }
.narrow { max-width: 720px; }
.section { padding-block: 3.5rem; }
.muted { color: var(--text-dim); }
.small { font-size: .85rem; }

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.skip-link {
  position: absolute; left: -9999px;
  background: var(--accent); color: #04222a; padding: .6rem 1rem; border-radius: 6px;
}
.skip-link:focus { left: 1rem; top: 1rem; z-index: 100; }

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

/* ── Header ─────────────────────────────────────────────────────────── */

.site-header {
  position: sticky; top: 0; z-index: 50;
  background: rgba(8, 12, 18, .82);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.header-inner {
  display: flex; align-items: center; justify-content: space-between;
  gap: 1rem; padding-block: .8rem;
}
.brand {
  display: flex; align-items: center; gap: .7rem;
  color: var(--text); font-weight: 650; letter-spacing: -.01em;
}
.brand:hover { text-decoration: none; color: #fff; }
.brand img { border-radius: 8px; border: 1px solid var(--border-lit); }
.site-header nav { display: flex; gap: 1.4rem; font-size: .94rem; }
.site-header nav a { color: var(--text-dim); }
.site-header nav a:hover { color: var(--accent); text-decoration: none; }

/* ── Hero ───────────────────────────────────────────────────────────── */

.hero { border-bottom: 1px solid var(--border); }
.hero-inner {
  display: flex; gap: 2.75rem; align-items: center;
  padding-block: 4rem 3.5rem;
}
.hero-art {
  border-radius: 18px; border: 1px solid var(--border-lit);
  box-shadow: 0 24px 60px rgba(0, 0, 0, .6), 0 0 0 1px rgba(34, 211, 238, .06);
  flex-shrink: 0;
}
.eyebrow {
  margin: 0 0 .6rem; text-transform: uppercase; letter-spacing: .14em;
  font-size: .74rem; font-weight: 600; color: var(--accent);
}
.hero h1 {
  margin: 0 0 .5rem; font-size: clamp(2rem, 4.6vw, 3.1rem);
  line-height: 1.08; letter-spacing: -.025em; font-weight: 750;
}
.tagline { margin: 0 0 1rem; font-size: 1.12rem; color: var(--text-dim); }
.hero-desc { margin: 0 0 1.6rem; color: var(--text-dim); max-width: 56ch; font-size: .98rem; }

.subscribe { display: flex; flex-wrap: wrap; gap: .7rem; }
.btn {
  display: inline-block; padding: .62rem 1.25rem; border-radius: 999px;
  border: 1px solid var(--border-lit); color: var(--text);
  font-size: .93rem; font-weight: 550; transition: all .15s ease;
}
.btn:hover { text-decoration: none; border-color: var(--accent); color: var(--accent); }
.btn-primary {
  background: var(--accent); border-color: var(--accent); color: #04222a; font-weight: 650;
}
.btn-primary:hover { background: #67e8f9; border-color: #67e8f9; color: #04222a; }

.feed-line {
  display: flex; align-items: center; gap: .7rem; flex-wrap: wrap;
  margin: 1.25rem 0 0; font-size: .84rem;
}
.mono {
  font-family: var(--mono); color: var(--text-dim);
  background: var(--bg-raised); border: 1px solid var(--border);
  border-radius: 6px; padding: .3rem .6rem;
}
.copy-btn {
  font: inherit; font-size: .8rem; cursor: pointer; color: var(--text-dim);
  background: transparent; border: 1px solid var(--border-lit);
  border-radius: 6px; padding: .3rem .7rem; transition: all .12s ease;
}
.copy-btn:hover { border-color: var(--accent); color: var(--accent); }
.copy-btn.copied { border-color: var(--accent); color: var(--accent); }

/* ── Host section ───────────────────────────────────────────────────── */

.host-section { border-top: 1px solid var(--border); background: #060a0f; }
.host-inner { padding-block: 3.5rem; display: flex; gap: 2.5rem; align-items: flex-start; }
.host-photo {
  border-radius: 50%; flex-shrink: 0;
  border: 1px solid var(--border-lit);
  box-shadow: 0 12px 36px rgba(0, 0, 0, .55), 0 0 0 6px rgba(34, 211, 238, .06);
}
.host-section h2 { margin: 0 0 .9rem; font-size: 1.6rem; letter-spacing: -.02em; }
.host-bio { color: var(--text-dim); max-width: 65ch; margin: 0 0 1.4rem; }
.host-photo-inline { float: right; margin: 0 0 1.25rem 1.75rem; }
.row-links { display: flex; flex-wrap: wrap; gap: .7rem; }

/* ── Article contents ───────────────────────────────────────────────── */

.article-head { margin-bottom: 1.5rem; }
.article-title { margin: 0 0 .3rem; font-size: 1.5rem; letter-spacing: -.02em; }
.contents {
  background: var(--bg-raised); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1.15rem 1.4rem;
}
.contents-label {
  margin: 0 0 .7rem; font-size: .74rem; text-transform: uppercase;
  letter-spacing: .12em; color: var(--text-mute); font-weight: 600;
}
.contents ol { margin: 0; padding-left: 1.2rem; display: grid; gap: .4rem; }
.contents li { color: var(--text-mute); font-size: .93rem; }
.contents a { color: var(--text-dim); }
.contents a:hover { color: var(--accent); text-decoration: none; }

/* Anchored headings shouldn't land under the sticky header */
.prose h2 { scroll-margin-top: 5rem; }

/* ── Episode list ───────────────────────────────────────────────────── */

.section-head {
  display: flex; align-items: baseline; justify-content: space-between;
  gap: 1rem; margin-bottom: 1.75rem;
}
.section-head h2 { margin: 0; font-size: 1.5rem; letter-spacing: -.015em; }

.episode-list { list-style: none; margin: 0; padding: 0; display: grid; gap: 1.1rem; }
.episode-card {
  display: flex; gap: 1.35rem;
  background: var(--bg-raised); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1.4rem;
  transition: border-color .15s ease, background .15s ease;
}
.episode-card:hover { border-color: var(--border-lit); background: var(--bg-hover); }
.ep-art img { border-radius: 10px; border: 1px solid var(--border-lit); display: block; }
.ep-body { min-width: 0; flex: 1; }
.ep-body h3 { margin: .35rem 0 .5rem; font-size: 1.3rem; letter-spacing: -.015em; line-height: 1.25; }
.ep-body h3 a { color: var(--text); }
.ep-body h3 a:hover { color: var(--accent); text-decoration: none; }
.ep-meta {
  margin: 0; display: flex; flex-wrap: wrap; gap: .9rem;
  font-size: .82rem; color: var(--text-mute);
}
.ep-num { color: var(--accent); font-weight: 600; }
.ep-summary { margin: 0 0 1rem; color: var(--text-dim); }

audio {
  width: 100%; height: 40px; margin-bottom: .9rem;
  border-radius: 8px; filter: invert(.92) hue-rotate(180deg) saturate(.7);
}

.topics { list-style: none; display: flex; flex-wrap: wrap; gap: .45rem; margin: 0; padding: 0; }
.topics li {
  font-size: .76rem; padding: .22rem .65rem; border-radius: 999px;
  background: var(--accent-glow); color: #7fdcea; border: 1px solid rgba(34, 211, 238, .18);
}

.empty {
  border: 1px dashed var(--border-lit); border-radius: var(--radius);
  padding: 2.5rem; text-align: center;
}

/* ── Episode page ───────────────────────────────────────────────────── */

/* One reading column for the whole page, so the header, article and nav all
   share a left edge instead of the prose floating centred inside a wider wrap. */
.episode-page .wrap { width: min(100% - 2.5rem, 760px); }

.ep-header { border-bottom: 1px solid var(--border); padding-block: 2.5rem 2.75rem; }
.breadcrumb { font-size: .85rem; color: var(--text-mute); margin: 0 0 1rem; }
.breadcrumb span { margin-inline: .4rem; }
.ep-header h1 {
  margin: 0 0 .75rem; font-size: clamp(1.85rem, 4vw, 2.7rem);
  line-height: 1.12; letter-spacing: -.025em; font-weight: 730; max-width: 20ch;
}
.ep-header .ep-meta { margin-bottom: 1.25rem; }
.lede { font-size: 1.1rem; color: var(--text-dim); max-width: 62ch; margin: 0 0 1.75rem; }

.player {
  background: var(--bg-raised); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1rem 1.15rem .5rem; margin-bottom: 1.25rem;
}
.player-note { margin: 0 0 .5rem; font-size: .85rem; color: var(--text-mute); }

/* ── Long-form article ──────────────────────────────────────────────── */

.prose { max-width: 100%; }
.prose.narrow, .narrow.prose { max-width: 720px; }
.prose h2 {
  margin: 2.75rem 0 .9rem; font-size: 1.55rem; letter-spacing: -.02em;
  line-height: 1.25; padding-top: .5rem; border-top: 1px solid var(--border);
}
.prose h3 { margin: 2rem 0 .7rem; font-size: 1.18rem; letter-spacing: -.01em; color: #cfe0ee; }
.prose p { margin: 0 0 1.25rem; }
.prose ul, .prose ol { margin: 0 0 1.25rem; padding-left: 1.4rem; }
.prose li { margin-bottom: .5rem; }
.prose strong { color: #fff; font-weight: 640; }
.prose a { text-decoration: underline; text-underline-offset: 2px; text-decoration-color: var(--accent-dim); }

.prose blockquote {
  margin: 1.75rem 0; padding: .3rem 0 .3rem 1.35rem;
  border-left: 3px solid var(--accent-dim); color: var(--text-dim); font-style: italic;
}
.prose code {
  font-family: var(--mono); font-size: .87em;
  background: #131b26; border: 1px solid var(--border);
  border-radius: 5px; padding: .12em .4em;
}
.prose pre {
  background: #0b1119; border: 1px solid var(--border); border-radius: 10px;
  padding: 1rem 1.15rem; overflow-x: auto; font-size: .87rem; line-height: 1.55;
}
.prose pre code { background: none; border: 0; padding: 0; }

/* Wide tables scroll rather than breaking the page */
.prose table {
  width: 100%; border-collapse: collapse; margin: 1.75rem 0;
  font-size: .92rem; display: block; overflow-x: auto;
}
.prose th, .prose td { border: 1px solid var(--border); padding: .6rem .85rem; text-align: left; }
.prose th { background: var(--bg-raised); font-weight: 620; color: #fff; }

.prose hr { border: 0; border-top: 1px solid var(--border); margin: 2.5rem 0; }

.papers { list-style: none; padding: 0; margin: 0; display: grid; gap: .6rem; }
.papers li {
  background: var(--bg-raised); border: 1px solid var(--border);
  border-radius: 10px; padding: .8rem 1rem; font-size: .94rem;
}

.research {
  background: var(--bg-raised); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1.1rem 1.35rem;
}
.research > summary {
  cursor: pointer; font-weight: 600; color: var(--text-dim); list-style-position: inside;
}
.research > summary:hover { color: var(--accent); }
.research[open] > summary { margin-bottom: 1.25rem; padding-bottom: .9rem; border-bottom: 1px solid var(--border); }

/* ── Episode nav ────────────────────────────────────────────────────── */

.ep-nav {
  display: grid; grid-template-columns: 1fr 1fr; gap: 1rem;
  padding-block: 2.5rem 4rem;
}
.ep-nav a {
  display: flex; flex-direction: column; gap: .2rem;
  background: var(--bg-raised); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1rem 1.2rem; color: var(--text);
}
.ep-nav a:hover { border-color: var(--accent); text-decoration: none; }
.nav-next { text-align: right; }

/* ── Footer ─────────────────────────────────────────────────────────── */

.site-footer {
  border-top: 1px solid var(--border); margin-top: 2rem;
  padding-block: 2.5rem 3rem; background: #060a0f;
}
.footer-inner {
  display: grid; grid-template-columns: 2fr 1fr 1fr; gap: 2.5rem;
  margin-bottom: 1.75rem;
}
.footer-about { max-width: 40ch; }
.footer-title { margin: 0 0 .25rem; font-weight: 650; }
.footer-inner p { margin: 0 0 .3rem; }
.footer-links { display: flex; flex-direction: column; gap: .45rem; font-size: .9rem; }
.footer-links .footer-title { color: var(--text-mute); text-transform: uppercase;
  letter-spacing: .1em; font-size: .72rem; margin-bottom: .5rem; }
.footer-links a { color: var(--text-dim); }
.footer-links a:hover { color: var(--accent); text-decoration: none; }

/* ── Responsive ─────────────────────────────────────────────────────── */

@media (max-width: 780px) {
  body { font-size: 16px; }
  .hero-inner { flex-direction: column; align-items: flex-start; gap: 1.75rem; padding-block: 2.5rem; }
  .hero-art { width: 168px; height: 168px; }
  .episode-card { flex-direction: column; gap: .9rem; }
  .ep-art img { width: 64px; height: 64px; }
  .ep-nav { grid-template-columns: 1fr; }
  .nav-next { text-align: left; }
  .site-header nav { gap: 1rem; font-size: .88rem; }
  .brand span { display: none; }
  .footer-inner { grid-template-columns: 1fr; gap: 1.75rem; }
  .host-inner { padding-block: 2.5rem; flex-direction: column; gap: 1.5rem; }
  .host-photo { width: 120px; height: 120px; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { transition: none !important; }
}