/* ============================================================
   6.62607015.com — The Planck Constant
   Dark, quantum-tech aesthetic
   ============================================================ */

:root{
  --bg:#05070d;
  --bg-2:#0a0e18;
  --panel:rgba(18,24,38,.55);
  --panel-solid:#0e1422;
  --line:rgba(120,160,220,.14);
  --line-strong:rgba(120,170,255,.30);
  --ink:#e8eef9;
  --ink-dim:#9aa8c4;
  --ink-faint:#5d6b86;
  --cyan:#39e0ff;
  --blue:#4d8bff;
  --violet:#9a7bff;
  --amber:#ffc24d;
  --red:#ff5d6c;
  --glow:0 0 24px rgba(57,224,255,.35);
  --radius:16px;
  --mono:'JetBrains Mono',ui-monospace,monospace;
  --sans:'Space Grotesk','Noto Sans SC',system-ui,sans-serif;
  --maxw:1080px;
}

*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
html,body{background:var(--bg);color:var(--ink);font-family:var(--sans);-webkit-font-smoothing:antialiased;overflow-x:hidden}
body{min-height:100vh;position:relative;line-height:1.7}

a{color:inherit;text-decoration:none}
::selection{background:rgba(57,224,255,.25);color:#fff}

/* ---------- background layers ---------- */
#bg-canvas{position:fixed;inset:0;width:100%;height:100%;z-index:-2;opacity:.55}
.grid-overlay{
  position:fixed;inset:0;z-index:-1;pointer-events:none;
  background-image:
    linear-gradient(rgba(80,120,200,.05) 1px,transparent 1px),
    linear-gradient(90deg,rgba(80,120,200,.05) 1px,transparent 1px);
  background-size:64px 64px;
  mask-image:radial-gradient(ellipse 80% 60% at 50% 35%,#000 30%,transparent 100%);
  -webkit-mask-image:radial-gradient(ellipse 80% 60% at 50% 35%,#000 30%,transparent 100%);
}

/* ---------- header ---------- */
.site-header{
  position:fixed;top:0;left:0;right:0;z-index:100;
  display:flex;align-items:center;gap:24px;
  padding:16px clamp(18px,4vw,48px);
  backdrop-filter:blur(14px);-webkit-backdrop-filter:blur(14px);
  background:linear-gradient(180deg,rgba(5,7,13,.85),rgba(5,7,13,.35));
  border-bottom:1px solid var(--line);
  transition:padding .3s;
}
.site-header.scrolled{padding-top:11px;padding-bottom:11px}

.brand{font-family:var(--mono);font-weight:700;font-size:16px;letter-spacing:.5px;display:flex;white-space:nowrap}
.brand-num{color:var(--ink)}
.brand-dot{color:var(--cyan);margin:0 1px}
.brand:hover .brand-num{color:var(--cyan)}

.nav-links{display:flex;gap:26px;margin-left:auto;margin-right:8px}
.nav-links a{
  font-size:13.5px;color:var(--ink-dim);font-weight:500;letter-spacing:.3px;
  position:relative;padding:6px 0;transition:color .2s;
}
.nav-links a::after{content:'';position:absolute;left:0;bottom:0;height:1px;width:0;background:var(--cyan);transition:width .25s}
.nav-links a:hover{color:var(--ink)}
.nav-links a:hover::after{width:100%}

.lang-switch{display:flex;align-items:center;gap:8px;font-family:var(--mono);font-size:13px}
.lang-btn{
  background:none;border:1px solid transparent;color:var(--ink-faint);
  font-family:var(--mono);font-size:13px;cursor:pointer;padding:3px 6px;border-radius:6px;
  transition:all .2s;font-weight:500;
}
.lang-btn:hover{color:var(--ink-dim)}
.lang-btn[aria-pressed="true"]{color:var(--cyan);border-color:var(--line-strong);box-shadow:0 0 12px rgba(57,224,255,.15)}
.lang-sep{color:var(--ink-faint);opacity:.5}

.nav-toggle{display:none;flex-direction:column;gap:5px;background:none;border:none;cursor:pointer;padding:6px;margin-left:4px}
.nav-toggle span{width:22px;height:2px;background:var(--ink);border-radius:2px;transition:.3s}
.nav-toggle[aria-expanded="true"] span:nth-child(1){transform:translateY(7px) rotate(45deg)}
.nav-toggle[aria-expanded="true"] span:nth-child(2){opacity:0}
.nav-toggle[aria-expanded="true"] span:nth-child(3){transform:translateY(-7px) rotate(-45deg)}

/* ---------- hero ---------- */
.hero{
  min-height:100vh;display:flex;align-items:center;justify-content:center;
  text-align:center;padding:120px 20px 80px;position:relative;
}
.hero-inner{max-width:880px}
.hero-kicker{
  font-family:var(--mono);font-size:12.5px;letter-spacing:3px;text-transform:uppercase;
  color:var(--cyan);margin-bottom:28px;opacity:0;animation:fadeUp .8s .1s forwards;
}
.hero-constant{
  font-family:var(--mono);font-weight:700;line-height:1;
  display:flex;align-items:flex-start;justify-content:center;gap:8px;flex-wrap:wrap;
  margin-bottom:10px;
  opacity:0;animation:fadeUp .9s .2s forwards;
}
.hc-int{
  font-size:clamp(2.6rem,9vw,6.2rem);
  background:linear-gradient(180deg,#fff 0%,#bfe9ff 60%,#39e0ff 100%);
  -webkit-background-clip:text;background-clip:text;color:transparent;
  text-shadow:0 0 60px rgba(57,224,255,.25);
  letter-spacing:-1px;
}
.hc-exp{font-size:clamp(1rem,3vw,1.8rem);color:var(--ink-dim);font-weight:500;margin-top:.6em}
.hc-exp sup{font-size:.6em}
.hero-unit{
  font-family:var(--mono);font-size:14px;color:var(--ink-faint);letter-spacing:2px;
  margin-bottom:40px;opacity:0;animation:fadeUp .9s .35s forwards;
}
.hero-title{
  font-size:clamp(1.6rem,4vw,2.6rem);font-weight:600;letter-spacing:-.5px;margin-bottom:16px;
  opacity:0;animation:fadeUp .9s .45s forwards;
}
.hero-sub{
  font-size:clamp(1rem,2vw,1.18rem);color:var(--ink-dim);max-width:620px;margin:0 auto 38px;
  opacity:0;animation:fadeUp .9s .55s forwards;
}
.hero-eq{
  display:inline-flex;align-items:center;gap:16px;
  padding:14px 26px;border:1px solid var(--line-strong);border-radius:999px;
  background:rgba(57,224,255,.04);
  opacity:0;animation:fadeUp .9s .65s forwards;
}
.hero-eq .eq-label{font-family:var(--mono);font-size:12px;color:var(--cyan);letter-spacing:1px}
.hero-eq .eq-math{font-size:18px;color:var(--ink)}
.hero-scroll{
  position:absolute;bottom:34px;left:50%;transform:translateX(-50%);
  display:flex;flex-direction:column;align-items:center;gap:10px;
  font-family:var(--mono);font-size:11px;color:var(--ink-faint);letter-spacing:2px;text-transform:uppercase;
}
.scroll-line{width:1px;height:42px;background:linear-gradient(180deg,var(--cyan),transparent);position:relative;overflow:hidden}
.scroll-line::after{content:'';position:absolute;top:-42px;left:0;width:1px;height:42px;background:var(--cyan);animation:scrollDot 2.2s infinite}

@keyframes scrollDot{0%{top:-42px}60%,100%{top:42px}}
@keyframes fadeUp{from{opacity:0;transform:translateY(18px)}to{opacity:1;transform:none}}
@keyframes pulse{0%,100%{opacity:.6}50%{opacity:1}}

/* ---------- content sections ---------- */
.content{max-width:var(--maxw);margin:0 auto;padding:40px clamp(18px,4vw,40px) 80px}
.section{
  padding:clamp(48px,8vw,90px) 0;border-top:1px solid var(--line);
  opacity:0;transform:translateY(30px);transition:opacity .8s,transform .8s;
}
.section.reveal{opacity:1;transform:none}
.section-head{display:flex;align-items:baseline;gap:18px;margin-bottom:34px;flex-wrap:wrap}
.section-no{
  font-family:var(--mono);font-size:13px;color:var(--cyan);
  border:1px solid var(--line-strong);border-radius:8px;padding:3px 10px;letter-spacing:1px;
}
.section-head h2{font-size:clamp(1.5rem,3.4vw,2.2rem);font-weight:600;letter-spacing:-.5px}
.section-body p{color:var(--ink-dim);font-size:1.05rem;margin-bottom:18px;max-width:75ch}
.section-body p:last-child{margin-bottom:0}

/* ---------- equation blocks ---------- */
.eq-block{
  margin:26px 0;padding:24px 26px;border:1px solid var(--line);border-radius:var(--radius);
  background:linear-gradient(180deg,rgba(20,28,46,.5),rgba(12,17,28,.4));
  position:relative;overflow:hidden;
}
.eq-block::before{content:'';position:absolute;left:0;top:0;bottom:0;width:3px;background:linear-gradient(180deg,var(--cyan),var(--violet))}
.eq-block-hero{text-align:center;padding:36px 26px}
.eq-tag{
  display:inline-block;font-family:var(--mono);font-size:11px;color:var(--cyan);
  letter-spacing:1.5px;text-transform:uppercase;margin-bottom:14px;
}
.eq{color:var(--ink);overflow-x:auto;padding:6px 0}
.eq-big{font-size:1.5rem}
.eq-note{color:var(--ink-faint);font-size:.92rem;margin-top:12px;font-style:italic}

/* fact grid */
.fact-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:14px;margin-top:28px}
.fact{
  border:1px solid var(--line);border-radius:12px;padding:18px;background:var(--panel);
  display:flex;flex-direction:column;gap:6px;
}
.fact-k{font-family:var(--mono);font-size:11px;color:var(--cyan);letter-spacing:1px;text-transform:uppercase}
.fact-v{font-family:var(--mono);font-size:15px;color:var(--ink);font-weight:500}

/* callout */
.callout{display:flex;gap:14px;align-items:flex-start;margin:28px 0;padding:18px 22px;border-radius:12px;border:1px solid}
.callout-warn{border-color:rgba(255,93,108,.35);background:rgba(255,93,108,.06)}
.callout-mark{
  flex:none;width:26px;height:26px;border-radius:50%;display:grid;place-items:center;
  font-family:var(--mono);font-weight:700;font-size:14px;
}
.callout-warn .callout-mark{background:rgba(255,93,108,.18);color:var(--red)}
.callout p{margin:0;color:var(--ink);font-size:1rem}

/* timeline */
.timeline{margin-top:30px;border-left:1px solid var(--line-strong);padding-left:24px;display:flex;flex-direction:column;gap:22px}
.tl-item{position:relative}
.tl-item::before{content:'';position:absolute;left:-29px;top:6px;width:9px;height:9px;border-radius:50%;background:var(--cyan);box-shadow:0 0 12px var(--cyan)}
.tl-date{font-family:var(--mono);font-size:12px;color:var(--cyan);letter-spacing:1px;display:block;margin-bottom:4px}
.tl-item p{margin:0}

/* limit grid */
.limit-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:16px;margin:28px 0}
.limit-card{border:1px solid var(--line);border-radius:12px;padding:20px;background:var(--panel)}
.limit-cond{font-family:var(--mono);font-size:12px;color:var(--amber);letter-spacing:.5px;display:block;margin-bottom:10px}
.limit-card p{margin-top:10px;font-size:.95rem}

/* unit grid */
.unit-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(140px,1fr));gap:14px;margin:28px 0}
.unit-card{
  border:1px solid var(--line);border-radius:12px;padding:22px 16px;text-align:center;background:var(--panel);
  transition:transform .25s,border-color .25s;
}
.unit-card:hover{transform:translateY(-4px);border-color:var(--line-strong)}
.unit-sym{display:block;font-family:var(--mono);font-size:1.8rem;font-weight:700;color:var(--cyan);margin-bottom:8px}
.unit-name{font-size:.86rem;color:var(--ink-dim);display:block}

/* legacy grid */
.legacy-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:18px;margin:30px 0}
.legacy-card{
  border:1px solid var(--line);border-radius:var(--radius);padding:24px;background:var(--panel);
  position:relative;overflow:hidden;transition:transform .3s,border-color .3s;
}
.legacy-card:hover{transform:translateY(-4px);border-color:var(--line-strong)}
.legacy-card::after{content:'';position:absolute;top:0;right:0;width:80px;height:80px;background:radial-gradient(circle at top right,rgba(154,123,255,.12),transparent 70%)}
.legacy-year{font-family:var(--mono);font-size:12px;color:var(--violet);letter-spacing:1.5px}
.legacy-card h3{font-size:1.15rem;font-weight:600;margin:8px 0 10px}
.legacy-card p{font-size:.95rem;color:var(--ink-dim);margin-bottom:14px}
.legacy-card .eq{font-size:.95rem;color:var(--cyan);border-top:1px solid var(--line);padding-top:12px}

/* planck units */
.planck-units{margin-top:34px;padding-top:28px;border-top:1px solid var(--line)}
.planck-units h3{font-size:1.2rem;font-weight:600;margin-bottom:10px}
.planck-units>p{margin-bottom:20px}
.pu-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:12px}
.pu{display:flex;flex-direction:column;gap:6px;padding:14px 16px;border:1px solid var(--line);border-radius:10px;background:rgba(12,17,28,.4)}
.pu-k{font-family:var(--mono);font-size:11px;color:var(--amber);letter-spacing:1px;text-transform:uppercase}
.pu-v{font-family:var(--mono);font-size:.92rem;color:var(--ink);overflow-x:auto}

.closing{
  margin-top:40px!important;padding:24px;border-left:2px solid var(--cyan);
  font-size:1.12rem!important;color:var(--ink)!important;font-style:italic;
}

/* ---------- footer ---------- */
.site-footer{border-top:1px solid var(--line);padding:60px 20px 50px;text-align:center;background:linear-gradient(180deg,transparent,rgba(10,14,24,.6))}
.footer-inner{max-width:var(--maxw);margin:0 auto}
.footer-brand{font-family:var(--mono);font-size:18px;font-weight:700;margin-bottom:14px}
.footer-brand .brand-suffix{color:var(--cyan)}
.footer-line{color:var(--ink-dim);max-width:480px;margin:0 auto 14px;font-size:1rem}
.footer-meta{font-family:var(--mono);font-size:11.5px;color:var(--ink-faint);letter-spacing:.5px}
.back-top{display:inline-block;margin-top:22px;font-family:var(--mono);font-size:12px;color:var(--cyan);letter-spacing:1px;border-bottom:1px solid transparent;transition:border-color .2s}
.back-top:hover{border-color:var(--cyan)}

/* MathJax sizing */
mjx-container{color:var(--ink)!important}
mjx-container[display="true"]{margin:.2em 0!important}
.eq-big mjx-container{font-size:130%!important}

/* ---------- responsive ---------- */
@media (max-width:820px){
  .nav-links{
    position:fixed;top:64px;left:0;right:0;flex-direction:column;gap:0;
    background:rgba(5,7,13,.97);backdrop-filter:blur(16px);
    border-bottom:1px solid var(--line);
    padding:8px clamp(18px,4vw,48px) 20px;
    transform:translateY(-120%);transition:transform .35s;visibility:hidden;
  }
  .nav-links.open{transform:none;visibility:visible}
  .nav-links a{padding:14px 0;border-bottom:1px solid var(--line)}
  .nav-toggle{display:flex}
  .nav-links{margin-left:0}
  .lang-switch{margin-left:auto}
  .section-body p{font-size:1rem}
}
@media (max-width:520px){
  .hero-eq{flex-direction:column;gap:8px;border-radius:14px}
  .hero-scroll{display:none}
  .eq-block{padding:18px 14px}
}

/* reduced motion */
@media (prefers-reduced-motion:reduce){
  *{animation:none!important;transition:none!important}
  .section{opacity:1;transform:none}
  html{scroll-behavior:auto}
}