/* VentiFlux Learning Center - shared stylesheet (brand-matched to ventiflux.com) */
:root{
  --navy:#0d4079; --navy-deep:#0a3261; --copper:#c85f2f; --copper-soft:#e5edf5;
  --paper:#f3f5f4; --ink:#142d38; --muted:#53656d; --surface:#ffffff;
  --line:#cbd5d3; --mint:#b9dae1;
  --font-sans:"IBM Plex Sans",-apple-system,"Segoe UI",sans-serif;
  --font-serif:"Newsreader",Georgia,serif;
  --font-mono:"IBM Plex Mono",ui-monospace,SFMono-Regular,Menlo,monospace;
  --shadow:0 2px 14px rgba(13,64,121,.08);
  --radius:14px;
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{font-family:var(--font-sans);color:var(--ink);background:var(--paper);line-height:1.7;-webkit-font-smoothing:antialiased}
a{color:var(--navy)}
img{max-width:100%}
.wrap{max-width:1180px;margin:0 auto;padding:0 24px}

/* ---------- top bar ---------- */
.vf-topbar{position:sticky;top:0;z-index:50;background:var(--surface);border-bottom:1px solid var(--line)}
.vf-topbar .wrap{display:flex;align-items:center;justify-content:space-between;height:68px}
.brand{display:flex;align-items:center;gap:12px;text-decoration:none;color:var(--navy);font-weight:700;font-size:1.25rem;letter-spacing:.02em}
.brand img{height:38px;width:auto}
.brand small{display:block;font-size:.68rem;font-weight:500;color:var(--muted);letter-spacing:.14em;text-transform:uppercase}
.vf-nav{display:flex;gap:26px;align-items:center}
.vf-nav a{text-decoration:none;color:var(--ink);font-weight:500;font-size:.95rem}
.vf-nav a:hover{color:var(--copper)}
.vf-nav .nav-cta{background:var(--copper);color:#fff;padding:10px 20px;border-radius:999px;font-weight:600}
.vf-nav .nav-cta:hover{background:var(--navy);color:#fff}

/* ---------- heroes ---------- */
.hero{background:linear-gradient(135deg,var(--navy) 0%,var(--navy-deep) 60%,#123f74 100%);color:#fff;padding:72px 0 64px;position:relative;overflow:hidden}
.hero::after{content:"";position:absolute;right:-120px;top:-120px;width:420px;height:420px;border-radius:50%;background:radial-gradient(circle,rgba(200,95,47,.35),transparent 70%)}
.kicker{display:inline-block;font-size:.75rem;font-weight:700;letter-spacing:.18em;text-transform:uppercase;color:#ffd9a8;margin-bottom:14px}
.hero h1{font-family:var(--font-serif);font-size:clamp(2rem,4.5vw,3.1rem);line-height:1.15;font-weight:600;max-width:820px;margin-bottom:16px}
.hero p.lead{font-size:1.08rem;color:#dbe7f3;max-width:760px}
.meta-row{display:flex;flex-wrap:wrap;gap:10px;margin-top:26px}
.meta-pill{display:inline-flex;align-items:center;gap:8px;background:rgba(255,255,255,.1);border:1px solid rgba(255,255,255,.22);color:#fff;font-size:.85rem;font-weight:500;padding:8px 16px;border-radius:999px}
.meta-pill.free{background:var(--copper);border-color:var(--copper);font-weight:700;letter-spacing:.06em}

/* ---------- course layout ---------- */
.course-layout{display:grid;grid-template-columns:280px 1fr;gap:40px;max-width:1180px;margin:0 auto;padding:48px 24px 80px;align-items:start}
.course-toc{position:sticky;top:92px;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:22px;box-shadow:var(--shadow);max-height:calc(100vh - 120px);overflow:auto}
.course-toc h2{font-size:.78rem;letter-spacing:.14em;text-transform:uppercase;color:var(--muted);margin-bottom:12px}
.course-toc ol{list-style:none}
.course-toc li{margin:0}
.course-toc a{display:block;text-decoration:none;color:var(--ink);font-size:.9rem;padding:8px 10px;border-radius:8px;border-left:3px solid transparent}
.course-toc a:hover{background:var(--copper-soft);border-left-color:var(--copper)}
.course-toc .toc-back{display:inline-block;margin-top:14px;font-size:.85rem;font-weight:600;color:var(--copper);text-decoration:none}

/* ---------- sessions ---------- */
.vf-session{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:36px;margin-bottom:28px;box-shadow:var(--shadow)}
.vf-session > .session-kicker{font-size:.75rem;font-weight:700;letter-spacing:.16em;text-transform:uppercase;color:var(--copper);margin-bottom:6px}
.vf-session > h3{font-family:var(--font-serif);font-size:1.65rem;line-height:1.3;color:var(--navy);margin-bottom:18px}
.session-objectives{background:var(--copper-soft);border-radius:10px;padding:20px 22px;margin-bottom:24px}
.session-objectives h4,.session-body h4{font-size:.82rem;letter-spacing:.12em;text-transform:uppercase;color:var(--navy);margin:0 0 10px}
.session-objectives ul{margin-left:20px}
.session-objectives li{margin-bottom:6px;font-size:.96rem}
.session-body p{margin-bottom:16px;font-size:1rem}
.session-body ul,.session-body ol{margin:0 0 16px 22px}
.session-body li{margin-bottom:6px}
.session-body h4{margin:26px 0 10px}
.equation{background:var(--paper);border-left:4px solid var(--copper);border-radius:0 10px 10px 0;padding:16px 20px;margin:20px 0;font-family:var(--font-mono);font-size:.98rem;overflow-x:auto}
.equation p{margin:0 0 10px;font-size:1.02rem}
.symbols{font-family:var(--font-sans);font-size:.88rem;margin:0}
.symbols dt{display:inline;font-weight:700;color:var(--navy);font-family:var(--font-mono);font-size:.85rem}
.symbols dd{display:inline;margin:0;color:var(--muted)}
.symbols dd::after{content:"";display:block;margin-bottom:4px}
.worked-example{background:#eef7f4;border:1px solid var(--mint);border-radius:10px;padding:22px;margin:24px 0}
.worked-example h4{color:#0d5c4d}
.design-note{background:#fdf3ec;border-left:4px solid var(--copper);border-radius:0 10px 10px 0;padding:18px 22px;margin:24px 0}
.design-note h4{color:var(--copper)}
.design-note p:last-child{margin-bottom:0}

/* ---------- references ---------- */
.vf-references{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:36px;margin-bottom:28px}
.vf-references > .session-kicker{font-size:.75rem;font-weight:700;letter-spacing:.16em;text-transform:uppercase;color:var(--copper);margin-bottom:6px}
.vf-references > h3{font-family:var(--font-serif);font-size:1.65rem;color:var(--navy);margin-bottom:14px}
.ref-note{font-size:.9rem;color:var(--muted);font-style:italic;margin-bottom:18px}
.ref-list{margin-left:22px}
.ref-list li{margin-bottom:10px;font-size:.94rem;color:var(--ink)}
.ref-list em{font-family:var(--font-serif)}

/* ---------- course footer nav ---------- */
.course-pager{display:flex;justify-content:space-between;gap:16px;margin-top:8px}
.course-pager a{flex:1;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:20px 22px;text-decoration:none;box-shadow:var(--shadow)}
.course-pager a:hover{border-color:var(--copper)}
.course-pager .pager-label{font-size:.75rem;letter-spacing:.12em;text-transform:uppercase;color:var(--muted);display:block;margin-bottom:6px}
.course-pager .pager-title{font-family:var(--font-serif);font-size:1.1rem;color:var(--navy);font-weight:600}
.course-pager a.next{text-align:right}

/* ---------- hub page ---------- */
.track{margin:56px 0}
.track-head{display:flex;align-items:baseline;gap:16px;margin-bottom:8px}
.track-head h2{font-family:var(--font-serif);font-size:1.7rem;color:var(--navy)}
.track-head .track-count{font-size:.85rem;color:var(--muted)}
.track-desc{color:var(--muted);max-width:760px;margin-bottom:24px}
.card-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(320px,1fr));gap:22px}
.course-card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:28px;display:flex;flex-direction:column;box-shadow:var(--shadow);transition:transform .15s ease,box-shadow .15s ease}
.course-card:hover{transform:translateY(-3px);box-shadow:0 8px 26px rgba(13,64,121,.14)}
.course-card .card-top{display:flex;justify-content:space-between;align-items:center;margin-bottom:14px}
.level{font-size:.75rem;font-weight:700;letter-spacing:.1em;text-transform:uppercase;color:var(--navy);background:var(--copper-soft);padding:5px 12px;border-radius:999px}
.free-badge{font-size:.75rem;font-weight:700;letter-spacing:.1em;color:#fff;background:var(--copper);padding:5px 12px;border-radius:999px}
.course-card h3{font-family:var(--font-serif);font-size:1.35rem;line-height:1.3;color:var(--navy);margin-bottom:10px}
.course-card h3 a{color:inherit;text-decoration:none}
.course-card h3 a:hover{color:var(--copper)}
.course-card p{font-size:.94rem;color:var(--muted);flex:1;margin-bottom:18px}
.card-meta{display:flex;flex-wrap:wrap;gap:14px;font-size:.84rem;color:var(--muted);margin-bottom:18px}
.card-meta strong{color:var(--ink)}
.card-link{align-self:flex-start;font-weight:700;color:var(--copper);text-decoration:none;font-size:.95rem}
.card-link:hover{color:var(--navy)}
.soon-note{background:var(--surface);border:1px dashed var(--copper);border-radius:var(--radius);padding:28px;margin:64px 0;color:var(--ink)}
.soon-note h2{font-family:var(--font-serif);color:var(--navy);font-size:1.4rem;margin-bottom:8px}
.hub-section{padding:64px 0 24px}

/* ---------- footer ---------- */
.vf-footer{background:var(--navy);color:#cfe0f2;padding:48px 0;margin-top:40px}
.vf-footer .wrap{display:flex;flex-wrap:wrap;gap:32px;justify-content:space-between;align-items:flex-start}
.vf-footer .fbrand{color:#fff;font-weight:700;font-size:1.2rem;margin-bottom:8px}
.vf-footer p{font-size:.9rem;max-width:420px}
.vf-footer a{color:#ffd9a8;text-decoration:none}
.vf-footer .fnav{display:flex;gap:22px}
.vf-footer .fnav a{color:#dbe7f3;font-size:.92rem}

/* ---------- responsive ---------- */
@media (max-width:960px){
  .course-layout{grid-template-columns:1fr}
  .course-toc{position:static;max-height:none}
  .vf-nav{gap:14px}
  .vf-nav a:not(.nav-cta){display:none}
  .vf-session,.vf-references{padding:26px 20px}
  .course-pager{flex-direction:column}
}