/* ============================================================
   HUICHANG — styles.css
   Design tokens, base, layout, components, responsive.
   Mobile-first. Site is fully functional without JS.
   ============================================================ */

/* ---------- Design tokens ---------- */
:root{
  --navy:#0A2540; --blue:#1E5F8E; --amber:#F59E0B;
  --bg:#F8FAFC; --text:#1F2937; --white:#FFFFFF;
  --muted:#64748B; --border:#E2E8F0;
  --maxw:1200px; --radius:12px;
  --shadow:0 4px 20px rgba(10,37,64,.08);
  --shadow-hover:0 8px 30px rgba(10,37,64,.15);
  --font-head:'Poppins',system-ui,sans-serif;
  --font-body:'Inter',system-ui,sans-serif;
}

/* ---------- Reset / base ---------- */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;scroll-padding-top:90px}
body{font-family:var(--font-body);color:var(--text);background:var(--white);
  line-height:1.65;font-size:1rem;-webkit-font-smoothing:antialiased}
h1,h2,h3,h4{font-family:var(--font-head);line-height:1.2;color:var(--navy);font-weight:700}
h1{font-size:clamp(2rem,5vw,3.4rem)}
h2{font-size:clamp(1.6rem,3.5vw,2.4rem)}
h3{font-size:1.25rem}
p{color:var(--text)}
a{color:var(--blue);text-decoration:none}
a:hover{color:var(--navy)}
img{max-width:100%;display:block}
ul{list-style:none}

/* ---------- Layout ---------- */
.container{max-width:var(--maxw);margin:0 auto;padding:0 1.5rem}
.section{padding:5rem 0}
.section--alt{background:var(--bg)}
.section__head{max-width:720px;margin:0 auto 3rem;text-align:center}
.eyebrow{display:inline-block;font-family:var(--font-head);font-weight:600;
  font-size:.8rem;letter-spacing:.12em;text-transform:uppercase;color:var(--amber);margin-bottom:.75rem}
.section__title{margin-bottom:1rem}
.section__lead{color:var(--muted);font-size:1.1rem}

/* ---------- Grids ---------- */
.grid{display:grid;gap:2rem}
.grid--2{grid-template-columns:repeat(auto-fit,minmax(280px,1fr))}
.grid--3{grid-template-columns:repeat(auto-fit,minmax(260px,1fr))}
.grid--4{grid-template-columns:repeat(auto-fit,minmax(220px,1fr))}
.grid--5{grid-template-columns:repeat(auto-fit,minmax(180px,1fr))}

/* ---------- Buttons ---------- */
.btn{display:inline-flex;align-items:center;gap:.5rem;font-family:var(--font-head);
  font-weight:600;font-size:1rem;padding:.85rem 1.6rem;border-radius:50px;
  border:2px solid transparent;cursor:pointer;transition:.25s;text-align:center}
.btn--primary{background:var(--amber);color:var(--navy)}
.btn--primary:hover{background:#E8920A;color:var(--navy);transform:translateY(-2px)}
.btn--ghost{background:transparent;color:var(--white);border-color:rgba(255,255,255,.6)}
.btn--ghost:hover{background:rgba(255,255,255,.1);color:var(--white)}
.btn--outline{background:transparent;color:var(--navy);border-color:var(--navy)}
.btn--outline:hover{background:var(--navy);color:var(--white)}

/* ---------- Cards ---------- */
.card{background:var(--white);border:1px solid var(--border);border-radius:var(--radius);
  overflow:hidden;box-shadow:var(--shadow)}
.card--hover{transition:.3s}
.card--hover:hover{transform:translateY(-6px);box-shadow:var(--shadow-hover);border-color:var(--blue)}

/* ---------- Stats ---------- */
.stat{text-align:center}
.stat__num{font-family:var(--font-head);font-weight:700;font-size:clamp(2.2rem,5vw,3.2rem);
  color:var(--amber);line-height:1}
.stat__label{color:var(--muted);margin-top:.5rem;font-size:.95rem}

/* ---------- Badge ---------- */
.badge{position:absolute;top:.75rem;left:.75rem;background:var(--amber);color:var(--navy);
  font-family:var(--font-head);font-weight:600;font-size:.7rem;letter-spacing:.08em;
  text-transform:uppercase;padding:.25rem .6rem;border-radius:50px}

/* ---------- Header / nav ---------- */
.nav{position:fixed;top:0;left:0;right:0;z-index:100;background:rgba(10,37,64,.95);
  backdrop-filter:blur(8px);transition:.3s}
.nav--scrolled{background:var(--navy);box-shadow:0 2px 20px rgba(0,0,0,.2)}
.nav__inner{display:flex;align-items:center;justify-content:space-between;
  max-width:var(--maxw);margin:0 auto;padding:0 1.5rem;height:72px}
.nav__logo{height:34px}
.nav__links{display:flex;align-items:center;gap:2rem}
.nav__link{color:rgba(255,255,255,.85);font-weight:500}
.nav__link:hover{color:var(--white)}
.nav__link[aria-current="page"]{color:var(--amber)}
.nav__cta{background:var(--amber);color:var(--navy);padding:.55rem 1.2rem;border-radius:50px;
  font-family:var(--font-head);font-weight:600}
.nav__cta:hover{background:#E8920A;color:var(--navy)}
.nav__toggle{display:none;background:none;border:none;cursor:pointer;
  flex-direction:column;gap:5px;padding:8px}
.nav__toggle span{width:24px;height:2px;background:var(--white);transition:.3s}

/* ---------- Footer ---------- */
.footer{background:var(--navy);color:rgba(255,255,255,.75);padding:4rem 0 2rem}
.footer h4{color:var(--white);margin-bottom:1rem;font-size:1rem}
.footer a{color:rgba(255,255,255,.75)}
.footer a:hover{color:var(--amber)}
.footer__grid{display:grid;gap:2rem;grid-template-columns:repeat(auto-fit,minmax(180px,1fr));
  margin-bottom:2.5rem}
.footer__bottom{border-top:1px solid rgba(255,255,255,.15);padding-top:1.5rem;
  text-align:center;font-size:.85rem;color:rgba(255,255,255,.5)}

/* ---------- Scroll reveal (progressively enhanced) ----------
   Content is visible by default. Only when JS confirms IntersectionObserver
   support does it add .js-io to <html>, which enables the hidden start
   state. This guarantees content is never permanently hidden by a missing/
   late observer. */
.reveal{transition:opacity .6s,transform .6s}
html.js-io .reveal{opacity:0;transform:translateY(24px)}
.reveal.is-visible,html.js-io .reveal.is-visible{opacity:1;transform:none}

/* ---------- Hero ---------- */
.hero{background:linear-gradient(135deg,#0A2540 0%,#1E5F8E 100%);color:var(--white);
  padding:9rem 0 6rem;position:relative;overflow:hidden}
.hero h1{color:var(--white);max-width:18ch}
.hero__lead{font-size:1.25rem;color:rgba(255,255,255,.85);max-width:60ch;margin:1.5rem 0 2.5rem}
.hero__actions{display:flex;flex-wrap:wrap;gap:1rem}

/* ---------- Product page: 2-level sidebar + grid ---------- */
.catnav{position:sticky;top:96px;align-self:start;background:var(--white);
  border:1px solid var(--border);border-radius:var(--radius);padding:1.5rem;
  box-shadow:var(--shadow);max-height:calc(100vh - 120px);overflow-y:auto}
.catnav__title{font-family:var(--font-head);font-weight:700;font-size:.75rem;
  letter-spacing:.1em;text-transform:uppercase;color:var(--muted);margin-bottom:1rem}
.catnav__cat{margin-bottom:1.25rem}
.catnav__catname{display:flex;align-items:center;gap:.5rem;font-family:var(--font-head);
  font-weight:600;font-size:.95rem;color:var(--navy);margin-bottom:.5rem}
.catnav__num{color:var(--amber);font-size:.8rem}
.catnav__sub{display:block;padding:.25rem 0 .25rem 1.5rem;font-size:.85rem;
  color:var(--muted);line-height:1.4}
.catnav__sub:hover{color:var(--blue)}
.catnav__sub.active{color:var(--blue);font-weight:600}
.products-layout{display:grid;grid-template-columns:260px 1fr;gap:2.5rem;align-items:start}
.subhead{margin-bottom:2rem;padding-bottom:1rem;border-bottom:2px solid var(--border)}
.subhead__cat{font-family:var(--font-head);font-weight:600;font-size:.8rem;
  letter-spacing:.1em;text-transform:uppercase;color:var(--amber)}
.subhead__name{margin:.25rem 0}
.subhead__count{color:var(--muted);font-size:.9rem}
.productcard{background:var(--white);border:1px solid var(--border);border-radius:var(--radius);
  padding:1.25rem;text-align:center;transition:.25s}
.productcard:hover{transform:translateY(-4px);box-shadow:var(--shadow-hover);border-color:var(--blue)}
.productcard__img{width:100%;aspect-ratio:1/1;object-fit:contain;background:var(--bg);
  border-radius:8px;margin-bottom:.75rem}
.productcard__placeholder{width:100%;aspect-ratio:1/1;background:var(--bg);border-radius:8px;
  margin-bottom:.75rem;display:flex;align-items:center;justify-content:center;
  color:var(--muted);font-family:var(--font-head);font-weight:600;font-size:.9rem;
  text-align:center;padding:1rem}
.productcard__model{font-weight:600;font-size:.95rem;color:var(--navy);word-break:break-all}
.productcard--textonly{padding:.85rem 1rem;display:flex;flex-direction:column;justify-content:center;min-height:0}
.productcard--textonly .productcard__model{font-size:1rem}
.productcard--textonly .productcard__spec{margin-top:.3rem}
.productcard__spec{color:var(--blue);font-size:.78rem;margin-top:.2rem;line-height:1.3}
.subsection{margin-bottom:4rem;scroll-margin-top:96px}
@media (max-width:1024px){
  .products-layout{grid-template-columns:1fr}
  .catnav{position:static;max-height:none;order:2}
}

/* ---------- Responsive ---------- */
@media (max-width:768px){
  .nav__links{position:fixed;inset:72px 0 auto 0;background:var(--navy);
    flex-direction:column;padding:2rem 1.5rem;gap:1.5rem;
    transform:translateY(-150%);transition:.3s}
  .nav__links.is-open{transform:none}
  .nav__toggle{display:flex}
}
@media (prefers-reduced-motion:reduce){
  *{animation:none!important;transition:none!important;scroll-behavior:auto!important}
  .reveal{opacity:1;transform:none}
}