/* ===== ACS Colloids 2027 — Save the Date — CU Boulder palette ===== */
:root{
  --ink:#1a1a1a; --slate:#2b2f33;
  --gold:#cfb87c; --gold-d:#b59f63;
  --paper:#ffffff; --paper-alt:#f4f2ec;
  --muted:#6b7177; --line:#e3e0d6; --maxw:1080px;
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif;
  color:var(--ink);line-height:1.6;background:var(--paper)}
img{max-width:100%;display:block}
a{color:#9a7d2e;text-decoration:none}
a:hover{text-decoration:underline}
.container{max-width:var(--maxw);margin:0 auto;padding:0 24px}
.narrow{max-width:760px}
.center{text-align:center}
.muted{color:var(--muted)}

/* ===== Header / nav ===== */
.site-header{position:sticky;top:0;z-index:50;background:rgba(20,22,24,.96);
  backdrop-filter:blur(6px);border-bottom:3px solid var(--gold)}
.nav-wrap{max-width:var(--maxw);margin:0 auto;padding:0 24px;display:flex;align-items:center;
  justify-content:space-between;height:62px}
.brand{color:#fff;font-weight:800;font-size:1.15rem;letter-spacing:.5px}
.brand span{color:var(--gold)} .brand:hover{text-decoration:none}
.nav{display:flex;gap:22px}
.nav a{color:#e8e8e8;font-size:.92rem;font-weight:500}
.nav a:hover{color:var(--gold);text-decoration:none}
.nav-toggle{display:none;background:none;border:0;color:#fff;font-size:1.6rem;cursor:pointer}

/* ===== Hero with rotating photos ===== */
.hero{position:relative;min-height:84vh;display:flex;align-items:center;justify-content:center;
  text-align:center;color:#fff;overflow:hidden;background:#1d2733}
.hero-slides{position:absolute;inset:0;z-index:0}
.hero-slides .slide{position:absolute;inset:0;width:100%;height:100%;object-fit:cover;
  opacity:0;transition:opacity 1.4s ease-in-out}
.hero-slides .slide.active{opacity:1}
.hero:after{content:"";position:absolute;inset:0;z-index:1;
  background:linear-gradient(rgba(15,20,28,.50),rgba(15,20,28,.68))}
.hero-overlay{position:relative;z-index:2;padding:40px 24px;max-width:900px}
.hero-kicker{text-transform:uppercase;letter-spacing:4px;font-size:.82rem;color:var(--gold);margin-bottom:14px}
.hero h1{font-size:clamp(1.9rem,4.6vw,3.1rem);font-weight:800;line-height:1.15;text-shadow:0 2px 18px rgba(0,0,0,.55)}
.hero h1 sup{font-size:.55em}
.hero-sub{font-size:1.35rem;font-style:italic;color:var(--gold);margin:.4rem 0 1rem}
.hero-meta{font-size:1.18rem;font-weight:600;margin-bottom:28px;text-shadow:0 1px 10px rgba(0,0,0,.5)}
.hero-credit{position:absolute;right:12px;bottom:10px;z-index:2;margin:0;font-size:.72rem;
  color:rgba(255,255,255,.72);background:rgba(0,0,0,.28);padding:3px 9px;border-radius:4px;cursor:default}

/* ===== Buttons ===== */
.btn{display:inline-block;padding:13px 30px;border-radius:6px;font-weight:700;font-size:.97rem;
  transition:.15s;border:2px solid transparent}
.btn:hover{text-decoration:none;transform:translateY(-1px)}
.btn-gold{background:var(--gold);color:#1a1a1a;border-color:var(--gold)}
.btn-gold:hover{background:var(--gold-d)}

/* ===== Sections ===== */
.section{padding:74px 0}
.section.alt{background:var(--paper-alt)}
.section h2{font-size:2rem;text-align:center;margin-bottom:1.2rem;position:relative;padding-bottom:14px}
.section h2:after{content:"";position:absolute;left:50%;bottom:0;transform:translateX(-50%);
  width:64px;height:3px;background:var(--gold)}
.section p{margin-bottom:1rem}

/* ===== Boulder / location ===== */
.why-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:22px;margin-top:30px}
.why{background:#fff;border:1px solid var(--line);border-top:3px solid var(--gold);
  border-radius:6px;padding:24px 22px;text-align:left}
.why h3{font-size:1.08rem;margin-bottom:10px;color:#2b2f33}
.why p{font-size:.92rem;color:#555;margin:0}

/* ===== Program ===== */
.schedule-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:18px;margin-top:26px}
.day{background:#fff;border:1px solid var(--line);border-radius:8px;padding:22px;text-align:center}
.day h3{color:#9a7d2e;font-size:1rem;margin-bottom:8px}
.day p{margin:0;color:#555}

/* ===== Coming soon strip ===== */
.coming{background:#16181a;color:#e6e6e6;padding:66px 0;text-align:center}
.coming h2{color:#fff;font-size:1.9rem;margin-bottom:14px}
.coming p{max-width:620px;margin:0 auto 24px;color:#b9bdc2}

/* ===== Organizers ===== */
.org-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:34px;margin-top:28px}
.org{text-align:center}
.org a{display:block;color:inherit;text-decoration:none}
.org img{width:100%;max-width:200px;aspect-ratio:4/5;object-fit:cover;object-position:center 18%;
  border-radius:10px;margin:0 auto 12px;box-shadow:0 4px 14px rgba(0,0,0,.12);transition:.15s ease}
.org a:hover img{transform:translateY(-3px);box-shadow:0 9px 22px rgba(0,0,0,.20)}
.org figcaption{font-size:1.05rem;line-height:1.35}
.org figcaption span{display:block;font-size:.84rem;color:var(--muted);font-weight:400;margin-top:2px}
.org a:hover figcaption strong{color:#9a7d2e}

/* ===== Footer ===== */
.site-footer{background:#16181a;color:#cfcfcf;padding:48px 0 24px;border-top:3px solid var(--gold)}
.footer-grid{display:flex;justify-content:space-between;align-items:center;gap:30px;flex-wrap:wrap}
.site-footer h3{color:#fff;margin-bottom:10px}
.site-footer a{color:var(--gold)}
.footer-logo img{background:#fff;padding:12px 16px;border-radius:8px;max-width:220px}
.footer-fine{margin-top:30px;padding-top:20px;border-top:1px solid #2c2f33;font-size:.82rem;color:#8b9097}

/* ===== Travel & lodging ===== */
.hotel-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:22px;margin-top:30px}
.hotel{background:#fff;border:1px solid var(--line);border-top:3px solid var(--gold);
  border-radius:6px;padding:26px 22px;text-align:center;display:flex;flex-direction:column}
.hotel h3{font-size:1.14rem;color:#2b2f33;margin-bottom:12px;min-height:2.7em;line-height:1.3;
  display:flex;flex-direction:column;align-items:center;justify-content:center}
.hotel h3 .sub{font-size:.92rem;font-weight:600;color:#5a4f2e}
.hotel .rate{font-size:1.7rem;font-weight:800;color:#9a7d2e;margin:0}
.hotel .rate span{font-size:.82rem;font-weight:600;color:var(--muted)}
.hotel-meta{font-size:.9rem;color:#555;margin:12px 0 14px;line-height:1.5}
.hotel .deadline{font-size:.92rem;color:#444;margin:0 0 16px}
.hotel .deadline strong{color:#9a7d2e}
.hotel .btn{align-self:center}
.hotel-contact{font-size:.82rem;color:var(--muted);margin-top:auto;padding-top:16px;line-height:1.5}
.hotel-contact a{word-break:break-word}

/* ===== Responsive ===== */
@media(max-width:820px){
  .nav{position:fixed;inset:62px 0 auto 0;flex-direction:column;background:#161819;
    padding:12px 24px 20px;gap:0;display:none}
  body.nav-open .nav{display:flex}
  .nav a{padding:12px 0;border-bottom:1px solid #2a2d2f}
  .nav-toggle{display:block}
  .why-grid{grid-template-columns:1fr 1fr}
  .schedule-grid{grid-template-columns:1fr 1fr}
  .org-grid{grid-template-columns:1fr 1fr}
  .hotel-grid{grid-template-columns:1fr}
}
@media(max-width:520px){
  .why-grid,.schedule-grid,.org-grid{grid-template-columns:1fr}
}