/* ==========================================================================
   CogSec — Cognitive Security for Human–AI Systems
   HCOMP 2026 / CI 2026 Workshop
   Dark-purple theme, matched to cstf.dev (Cognitive Security Task Force)
   ========================================================================== */

:root {
  /* Core palette pulled from cstf.dev */
  --bg:         #0d0120;   /* page background (darkest) */
  --bg-alt:     #150826;   /* alternating sections */
  --surface:    #1c1030;   /* cards */
  --surface-2:  #241638;   /* raised / feature rows */
  --line:       #2f1f47;   /* borders */
  --line-soft:  #241636;

  --brand:      #6e11b0;   /* deep purple — buttons */
  --brand-hi:   #7c1fc4;   /* hover */
  --brand-deep: #59168b;   /* deep purple accents */
  --accent:     #c07eff;   /* bright lavender — primary accent */
  --accent-2:   #c4b5fd;   /* soft violet — secondary accent */

  --ink:        #f5f1fb;   /* headings on dark */
  --ink-soft:   #d3c9e6;   /* body text */
  --muted:      #9a8cb5;   /* secondary text */

  --ring:       rgba(192,126,255,.16);
  --shadow:     0 1px 2px rgba(0,0,0,.4), 0 10px 34px rgba(10,2,24,.55);
  --maxw:       1080px;
  --radius:     14px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 84px; }

body {
  margin: 0;
  font-family: var(--font);
  color: var(--ink-soft);
  background: var(--bg);
  line-height: 1.62;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  transition: background-color .2s ease, color .2s ease;
}

h1, h2, h3, h4 { color: var(--ink); line-height: 1.2; font-weight: 700; letter-spacing: -0.01em; }
p { color: var(--ink-soft); }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
em { color: var(--accent-2); font-style: italic; }
strong { color: var(--ink); }

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }

/* ---------- Nav ---------------------------------------------------------- */
.nav {
  position: sticky; top: 0; z-index: 50;
  background: rgba(13,1,32,.78);
  backdrop-filter: saturate(160%) blur(14px);
  -webkit-backdrop-filter: saturate(160%) blur(14px);
  border-bottom: 1px solid var(--line);
}
.nav .wrap { display: flex; align-items: center; justify-content: space-between; height: 64px; }
.brand { display: flex; align-items: baseline; gap: 10px; font-weight: 800; color: var(--ink); letter-spacing: -0.02em; }
.brand .mark { font-size: 1.15rem; color: var(--accent); }
.brand .sub { font-size: .74rem; font-weight: 600; color: var(--muted); letter-spacing: .04em; text-transform: uppercase; }
.brand:hover { text-decoration: none; }
.nav-links { display: flex; align-items: center; gap: 4px; }
.nav-links a {
  color: var(--ink-soft); font-weight: 600; font-size: .9rem;
  padding: 8px 12px; border-radius: 8px;
}
.nav-links a:hover { background: var(--surface); color: #fff; text-decoration: none; }
.nav-links a.cta {
  background: var(--brand); color: #fff; margin-left: 6px;
}
.nav-links a.cta:hover { background: var(--brand-hi); }
.nav-right { display: flex; align-items: center; gap: 8px; }
.theme-toggle {
  background: rgba(255,255,255,.04); border: 1px solid var(--line); color: var(--ink);
  width: 38px; height: 38px; border-radius: 9px; cursor: pointer; font-size: 1rem;
  display: inline-grid; place-items: center; line-height: 1;
}
.theme-toggle:hover { background: var(--surface); border-color: var(--brand-deep); }
.nav-toggle { display: none; }

/* ---------- Hero --------------------------------------------------------- */
.hero {
  position: relative; overflow: hidden;
  background:
    radial-gradient(1100px 480px at 80% -12%, rgba(192,126,255,.20), transparent 60%),
    radial-gradient(900px 460px at 6% 108%, rgba(110,17,176,.30), transparent 58%),
    linear-gradient(180deg, #12042a 0%, #0d0120 100%);
  border-bottom: 1px solid var(--line);
}
.hero .wrap { padding: 76px 24px 68px; }
.eyebrow {
  display: inline-flex; align-items: center; gap: 12px;
  font-size: .8rem; font-weight: 700; letter-spacing: .14em; text-transform: uppercase;
  color: var(--accent-2);
}
.eyebrow::before { content: ""; width: 30px; height: 2px; background: var(--accent); }
.hero h1 {
  font-size: clamp(2.1rem, 4.6vw, 3.4rem);
  margin: 22px 0 8px; max-width: 16ch; color: var(--ink);
}
.hero .lede-title { color: var(--accent); }
.hero .tagline { font-size: 1.18rem; color: var(--ink-soft); max-width: 60ch; margin: 0 0 22px; }
.hero .meta { display: flex; flex-wrap: wrap; gap: 10px 22px; margin: 26px 0 30px; }
.hero .meta div { font-size: .95rem; color: var(--ink); }
.hero .meta strong { display: block; font-size: .72rem; text-transform: uppercase; letter-spacing: .05em; color: var(--muted); font-weight: 700; margin-bottom: 2px; }
.btn-row { display: flex; flex-wrap: wrap; gap: 12px; }
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  font-weight: 700; font-size: .95rem; padding: 12px 20px; border-radius: 10px;
  border: 1px solid transparent; cursor: pointer;
}
.btn-primary { background: var(--brand); color: #fff; box-shadow: var(--shadow); }
.btn-primary:hover { background: var(--brand-hi); text-decoration: none; }
.btn-ghost { background: rgba(255,255,255,.03); color: var(--accent-2); border-color: var(--line); }
.btn-ghost:hover { background: var(--surface); text-decoration: none; }

/* ---------- Sections ----------------------------------------------------- */
section { padding: 68px 0; border-bottom: 1px solid var(--line-soft); }
section.alt { background: var(--bg-alt); }
.section-head { max-width: 62ch; margin-bottom: 34px; }
.kicker { font-size: .78rem; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--accent); }
.section-head h2 { font-size: clamp(1.6rem, 3vw, 2.1rem); margin: 8px 0 12px; color: var(--ink); }
.section-head p { font-size: 1.05rem; margin: 0; color: var(--muted); }
.lead { font-size: 1.12rem; color: var(--ink-soft); max-width: 68ch; }

/* ---------- Cards / grid ------------------------------------------------- */
.grid { display: grid; gap: 20px; }
.grid.cols-2 { grid-template-columns: repeat(2, 1fr); }
.grid.cols-3 { grid-template-columns: repeat(3, 1fr); }
.card {
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 24px; box-shadow: var(--shadow); transition: border-color .18s ease, transform .18s ease;
}
.card:hover { border-color: var(--brand-deep); transform: translateY(-2px); }
.card h3 { font-size: 1.06rem; margin: 0 0 8px; color: var(--ink); }
.card p { margin: 0; font-size: .96rem; }
.card .tag {
  display: inline-block; font-size: .72rem; font-weight: 700; letter-spacing: .04em;
  text-transform: uppercase; color: var(--accent-2); background: rgba(192,126,255,.10);
  padding: 4px 10px; border-radius: 999px; margin-bottom: 12px;
}

/* Objectives list */
.obj { display: grid; gap: 14px; grid-template-columns: repeat(2, 1fr); }
.obj li { list-style: none; display: flex; gap: 14px; align-items: flex-start; }
.obj .n {
  flex: none; width: 30px; height: 30px; border-radius: 8px;
  background: linear-gradient(135deg, var(--brand), var(--accent)); color: #fff; font-weight: 800; font-size: .9rem;
  display: grid; place-items: center;
}
.obj span.t { color: var(--ink-soft); font-size: .98rem; }
ul.plain { padding: 0; margin: 0; }

/* ---------- Program ------------------------------------------------------ */
.notice {
  display: flex; gap: 12px; align-items: flex-start;
  background: rgba(192,126,255,.07); border: 1px solid var(--brand-deep); color: var(--accent-2);
  padding: 14px 18px; border-radius: 12px; font-size: .95rem; margin-bottom: 28px;
}
.notice strong { color: var(--ink); }
.agenda { border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; background: var(--surface); box-shadow: var(--shadow); }
.slot { display: grid; grid-template-columns: 132px 1fr 66px; gap: 18px; align-items: baseline; padding: 16px 22px; border-top: 1px solid var(--line-soft); }
.slot:first-child { border-top: none; }
.slot .dur { color: var(--muted); font-size: .82rem; font-weight: 600; text-align: right; white-space: nowrap; }
.slot .time { color: var(--accent); font-weight: 700; font-size: .9rem; }
.slot .what h4 { margin: 0 0 3px; font-size: 1.02rem; color: var(--ink); }
.slot .what p { margin: 0; font-size: .92rem; color: var(--muted); }
.slot.feature { background: var(--surface-2); }
.slot.break { background: rgba(255,255,255,.02); }
.slot.break .what h4 { font-weight: 600; color: var(--ink-soft); }

/* ---------- Speakers ----------------------------------------------------- */
.people { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.person {
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 22px; box-shadow: var(--shadow); transition: border-color .18s ease, transform .18s ease;
}
.person:hover { border-color: var(--brand-deep); transform: translateY(-2px); }
.person .avatar {
  width: 52px; height: 52px; border-radius: 50%; display: grid; place-items: center;
  font-weight: 800; color: #fff; font-size: 1.05rem; margin-bottom: 14px;
  background: linear-gradient(135deg, var(--brand-deep), var(--accent));
}
.person h3 { font-size: 1.05rem; margin: 0 0 2px; color: var(--ink); }
.avatar img { width: 100%; height: 100%; object-fit: cover; border-radius: 50%; display: block; }
.person .role { font-size: .86rem; color: var(--muted); margin: 0 0 10px; }
.person p.bio { font-size: .92rem; margin: 0; color: var(--ink-soft); }
.badge {
  display: inline-flex; align-items: center; gap: 8px; font-size: .72rem; font-weight: 700;
  letter-spacing: .09em; text-transform: uppercase; color: var(--muted); margin-bottom: 14px;
}
.badge::before {
  content: ""; flex: none; width: 7px; height: 7px; border-radius: 50%; background: var(--accent);
}
.badge.confirmed::before { background: #3ecf8e; box-shadow: 0 0 0 3px rgba(62,207,142,.16); }
.badge.invited::before { background: var(--accent); }

/* ---------- CfP / dates -------------------------------------------------- */
.dates { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; margin-top: 8px; }
.date-card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 20px; text-align: center; box-shadow: var(--shadow); }
.date-card .d { font-size: 1.02rem; font-weight: 800; color: var(--accent); }
.date-card .l { font-size: .8rem; color: var(--muted); text-transform: uppercase; letter-spacing: .04em; font-weight: 600; margin-top: 4px; }
.callout {
  background: linear-gradient(135deg, #59168b, #6e11b0 55%, #8a2be0); color: #fff;
  border: 1px solid var(--brand-hi);
  border-radius: var(--radius); padding: 34px; margin-top: 30px;
}
.callout h3 { color: #fff; margin: 0 0 8px; font-size: 1.3rem; }
.callout p { color: rgba(255,255,255,.92); margin: 0 0 18px; max-width: 62ch; }
.callout strong { color: #fff; }
.callout .btn-primary { background: #fff; color: var(--brand); }
.callout .btn-primary:hover { background: #f0e8fb; }

/* ---------- Footer ------------------------------------------------------- */
footer { background: #08010f; color: #cfc5e0; padding: 48px 0 34px; border: none; border-top: 1px solid #2f1f47; }
footer h4 { color: #fff; font-size: .95rem; margin: 0 0 12px; }
footer a { color: #c4b5fd; }
footer .cols { display: grid; grid-template-columns: 2fr 1fr 1fr; gap: 32px; }
footer p { color: #9a8cb5; font-size: .92rem; margin: 0 0 8px; }
footer ul { list-style: none; padding: 0; margin: 0; }
footer li { margin-bottom: 7px; font-size: .92rem; color: #cfc5e0; }
footer .fine { margin-top: 34px; padding-top: 20px; border-top: 1px solid #2f1f47; font-size: .82rem; color: #8a7ea5; }

/* ---------- Light theme -------------------------------------------------- */
:root[data-theme="light"] {
  --bg:         #ffffff;
  --bg-alt:     #f6f2fc;
  --surface:    #ffffff;
  --surface-2:  #f3edfb;
  --line:       #e7ddf4;
  --line-soft:  #efe8f8;
  --brand:      #6e11b0;
  --brand-hi:   #59168b;
  --brand-deep: #b98fe0;
  --accent:     #7c1fc4;
  --accent-2:   #6e11b0;
  --ink:        #1a0a2e;
  --ink-soft:   #3f3357;
  --muted:      #6b6080;
  --ring:       rgba(110,17,176,.14);
  --shadow:     0 1px 2px rgba(26,10,46,.06), 0 8px 26px rgba(26,10,46,.08);
}
:root[data-theme="light"] .nav { background: rgba(255,255,255,.85); }
:root[data-theme="light"] .hero {
  background:
    radial-gradient(1100px 480px at 80% -12%, rgba(192,126,255,.18), transparent 60%),
    radial-gradient(900px 460px at 6% 108%, rgba(110,17,176,.10), transparent 58%),
    linear-gradient(180deg, #faf7fe 0%, #f2ecfa 100%);
}
:root[data-theme="light"] .btn-ghost { background: #fff; }
:root[data-theme="light"] .theme-toggle { background: #fff; }
:root[data-theme="light"] .theme-toggle:hover { background: var(--surface-2); }
:root[data-theme="light"] .slot.break { background: #faf7fe; }
:root[data-theme="light"] .slot.break .what h4 { color: var(--ink-soft); }

/* ---------- Responsive --------------------------------------------------- */
@media (max-width: 860px) {
  .grid.cols-3, .grid.cols-2, .people, .obj, .dates { grid-template-columns: 1fr; }
  .people { grid-template-columns: repeat(2, 1fr); }
  .dates { grid-template-columns: repeat(2, 1fr); }
  footer .cols { grid-template-columns: 1fr; }
  .nav-links { display: none; }
  .nav-links.open {
    display: flex; flex-direction: column; align-items: stretch;
    position: absolute; top: 64px; left: 0; right: 0; background: var(--bg);
    border-bottom: 1px solid var(--line); padding: 10px 16px; gap: 2px;
  }
  .nav-toggle {
    display: inline-flex; background: none; border: 1px solid var(--line);
    border-radius: 8px; padding: 8px 10px; cursor: pointer; font-size: 1.1rem; color: var(--ink);
  }
}
@media (max-width: 560px) {
  .people { grid-template-columns: 1fr; }
  .slot { grid-template-columns: 96px 1fr; }
  .slot .dur { display: none; }
  .hero .wrap { padding: 56px 20px 48px; }
}