/* =========================================================================
   Lev Landau — biographical site
   Intellectual-modern: light paper, ink, a cool "quantum" gradient.
   Brand glyph λ = the lambda-point of superfluid helium.
   ========================================================================= */

:root{
  --paper:#f4f5f7;
  --paper-2:#eaecf0;
  --card:#ffffff;
  --ink:#121319;
  --ink-soft:#363943;
  --muted:#6d7280;
  --faint:#9aa0ab;
  --line:rgba(18,19,25,.12);
  --line-2:rgba(18,19,25,.07);

  /* quantum / superfluid gradient: order ........ disorder */
  --c0:#1e40af;   /* deep blue */
  --c1:#0891b2;   /* cyan      */
  --c2:#7c3aed;   /* violet    */
  --c3:#0ea5e9;   /* sky       */
  --accent:var(--c0);
  --grad:linear-gradient(100deg,var(--c0),var(--c1) 48%,var(--c2));
  --grad-soft:linear-gradient(100deg,rgba(30,64,175,.14),rgba(8,145,178,.12) 48%,rgba(124,58,237,.14));

  --serif:"Fraunces",Georgia,"Times New Roman",serif;
  --sans:"Inter",system-ui,-apple-system,"Segoe UI",sans-serif;
  --mono:"JetBrains Mono",ui-monospace,"SFMono-Regular",Menlo,monospace;
  --he:"Frank Ruhl Libre","Noto Sans Hebrew",serif;

  --wrap:1140px;
  --r:18px;
  --shadow:0 1px 2px rgba(18,19,25,.04),0 18px 50px -24px rgba(18,19,25,.24);
  --shadow-sm:0 1px 2px rgba(18,19,25,.05),0 8px 24px -16px rgba(18,19,25,.26);
}

*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{
  font-family:var(--sans);background:var(--paper);color:var(--ink);
  line-height:1.65;font-size:17px;-webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;overflow-x:hidden;
}
img{max-width:100%;display:block}
a{color:inherit;text-decoration:none}
::selection{background:rgba(124,58,237,.20)}

.wrap{max-width:var(--wrap);margin-inline:auto;padding-inline:clamp(1.1rem,4vw,2rem)}
.tight{max-width:780px}

h1,h2,h3,h4{font-family:var(--serif);font-weight:560;line-height:1.08;letter-spacing:-.01em}
h1{font-size:clamp(2.5rem,6.2vw,4.6rem);font-weight:600}
h2{font-size:clamp(1.9rem,3.6vw,2.9rem)}
h3{font-size:clamp(1.25rem,2vw,1.55rem)}
p{color:var(--ink-soft)}
.lede{font-size:clamp(1.12rem,1.7vw,1.32rem);color:var(--ink-soft);line-height:1.6}
.mono{font-family:var(--mono)}
.eyebrow{font-family:var(--mono);font-size:.74rem;letter-spacing:.22em;text-transform:uppercase;
  color:var(--accent);font-weight:600}
.grad-text{background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent}

.topbar{position:sticky;top:0;z-index:50;display:flex;align-items:center;justify-content:space-between;
  gap:1rem;padding:.7rem clamp(1.1rem,4vw,2rem);background:rgba(244,245,247,.82);
  backdrop-filter:saturate(1.4) blur(14px);border-bottom:1px solid var(--line-2)}
.brand{display:flex;align-items:center;gap:.6rem;font-weight:600;letter-spacing:-.01em}
.brand .mu{font-family:var(--serif);font-size:1.5rem;line-height:1;
  background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent}
.brand small{display:block;font-family:var(--mono);font-size:.6rem;letter-spacing:.18em;
  text-transform:uppercase;color:var(--muted);font-weight:500;margin-top:1px}
.nav{display:flex;gap:.3rem;align-items:center}
.nav a{font-size:.93rem;color:var(--ink-soft);padding:.45rem .7rem;border-radius:9px;
  transition:background .2s,color .2s;font-weight:450}
.nav a:hover{background:var(--paper-2);color:var(--ink)}
.nav a.active{color:var(--accent);font-weight:600}
.controls{display:flex;align-items:center;gap:.5rem}
.langs{display:flex;background:var(--paper-2);border:1px solid var(--line-2);border-radius:999px;padding:3px}
.langs button,.langs a{border:0;background:transparent;cursor:pointer;font:inherit;font-size:.78rem;font-weight:600;
  color:var(--muted);padding:.28rem .56rem;border-radius:999px;transition:.18s;line-height:1;
  text-decoration:none;display:inline-block}
.langs button:hover,.langs a:hover{color:var(--ink)}
.langs button.on,.langs a.on{background:#fff;color:var(--accent);box-shadow:var(--shadow-sm)}
.burger{display:none;border:1px solid var(--line);background:#fff;border-radius:10px;width:40px;height:40px;
  cursor:pointer;color:var(--ink);align-items:center;justify-content:center}
.burger svg{width:20px;height:20px}

.hero{position:relative;padding:clamp(3rem,8vw,6rem) 0 clamp(2.5rem,6vw,4.5rem);overflow:hidden}
.hero::before{content:"";position:absolute;inset:-30% -10% auto -10%;height:120%;z-index:-1;
  background:radial-gradient(60% 60% at 78% 12%,rgba(124,58,237,.13),transparent 60%),
             radial-gradient(50% 50% at 12% 8%,rgba(30,64,175,.13),transparent 60%),
             radial-gradient(45% 45% at 70% 90%,rgba(8,145,178,.11),transparent 60%);filter:blur(6px)}
.hero-grid{display:grid;grid-template-columns:1.35fr .9fr;gap:clamp(1.5rem,4vw,3.5rem);align-items:center}
.hero h1{margin:.5rem 0 .2rem}
.names-mini{display:flex;flex-wrap:wrap;gap:.35rem .9rem;margin-top:.7rem;color:var(--muted);font-size:.92rem}
.names-mini span{display:inline-flex;align-items:center;gap:.4rem}
.names-mini i{font-style:normal;color:var(--faint)}
.dates{font-family:var(--mono);font-size:1rem;color:var(--accent);margin-top:1.1rem;letter-spacing:.04em}
.hero-quote{margin-top:1.6rem;padding-inline-start:1.1rem;border-inline-start:3px solid transparent;
  border-image:var(--grad) 1;font-family:var(--serif);font-style:italic;
  font-size:clamp(1.05rem,1.6vw,1.28rem);color:var(--ink);line-height:1.45;max-width:44ch}
.portrait-frame{position:relative;justify-self:center}
.portrait-frame img{width:min(330px,72vw);border-radius:20px;box-shadow:var(--shadow);
  border:1px solid var(--line);background:#fff}
.portrait-frame::after{content:"λ";position:absolute;font-family:var(--serif);font-size:5rem;
  inset-block-end:-22px;inset-inline-end:-14px;
  background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent;opacity:.9}
.portrait-cap{margin-top:.7rem;font-size:.74rem;color:var(--faint);text-align:center;font-family:var(--mono)}

.btn-row{display:flex;flex-wrap:wrap;gap:.7rem;margin-top:1.8rem}
.btn{display:inline-flex;align-items:center;gap:.5rem;font-weight:550;font-size:.95rem;
  padding:.72rem 1.15rem;border-radius:12px;border:1px solid transparent;cursor:pointer;
  transition:transform .18s,box-shadow .2s,background .2s}
.btn-primary{background:var(--ink);color:#fff}
.btn-primary:hover{transform:translateY(-2px);box-shadow:0 12px 30px -12px rgba(18,19,25,.5)}
.btn-ghost{background:#fff;border-color:var(--line);color:var(--ink)}
.btn-ghost:hover{transform:translateY(-2px);box-shadow:var(--shadow-sm)}
.btn svg{width:17px;height:17px}

section{padding-block:clamp(2.8rem,6vw,5rem)}
.sec-head{max-width:680px;margin-bottom:2.2rem}
.sec-head h2{margin-top:.5rem}
.sec-head p{margin-top:.8rem}
.divider{height:1px;background:var(--line-2);max-width:var(--wrap);margin-inline:auto}

.tl-strip{display:grid;grid-template-columns:repeat(6,1fr);gap:0;border-top:1px solid var(--line);
  border-bottom:1px solid var(--line)}
.tl-strip .tl{padding:1.3rem 1rem;border-inline-start:1px solid var(--line-2);position:relative}
.tl-strip .tl:first-child{border-inline-start:0}
.tl-strip .tl b{font-family:var(--mono);color:var(--accent);font-size:.92rem;display:block}
.tl-strip .tl span{font-size:.86rem;color:var(--muted);display:block;margin-top:.3rem;line-height:1.4}

.cards{display:grid;grid-template-columns:repeat(3,1fr);gap:1.1rem}
.card{background:var(--card);border:1px solid var(--line-2);border-radius:var(--r);padding:1.6rem;
  display:flex;flex-direction:column;gap:.6rem;box-shadow:var(--shadow-sm);
  transition:transform .2s,box-shadow .25s,border-color .2s;position:relative;overflow:hidden}
.card::before{content:"";position:absolute;inset-block-start:0;inset-inline:0;height:3px;background:var(--grad);
  transform:scaleX(0);transform-origin:inline-start;transition:transform .35s}
.card:hover{transform:translateY(-4px);box-shadow:var(--shadow);border-color:var(--line)}
.card:hover::before{transform:scaleX(1)}
.card .num{font-family:var(--mono);font-size:.78rem;color:var(--faint)}
.card h3{font-size:1.22rem}
.card p{font-size:.95rem;color:var(--muted)}
.card .go{margin-top:auto;font-weight:600;color:var(--accent);font-size:.9rem;display:inline-flex;gap:.35rem;align-items:center}
.card .go svg{width:15px;height:15px;transition:transform .2s}
.card:hover .go svg{transform:translateX(3px)}

.prose p{margin-bottom:1.1rem;max-width:70ch}
.prose h3{margin:2.2rem 0 .8rem}
.prose strong{color:var(--ink);font-weight:600}
.prose .first-letter::first-letter{font-family:var(--serif);font-size:3.4rem;float:inline-start;line-height:.8;
  padding-inline-end:.12em;padding-block-start:.1em;
  background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent}

.pull{font-family:var(--serif);font-style:italic;font-size:clamp(1.3rem,2.4vw,1.9rem);line-height:1.34;
  color:var(--ink);margin:2rem 0;padding-inline-start:1.3rem;border-inline-start:4px solid transparent;border-image:var(--grad) 1}
.pull cite{display:block;font-family:var(--mono);font-style:normal;font-size:.8rem;letter-spacing:.06em;color:var(--muted);margin-top:.8rem}

.dispute{display:grid;grid-template-columns:1fr 1fr;gap:1rem;margin:1.8rem 0}
.dispute .f{background:var(--card);border:1px solid var(--line-2);border-radius:14px;padding:1.3rem}
.dispute .f h4{font-family:var(--mono);font-size:.74rem;letter-spacing:.14em;text-transform:uppercase;
  color:var(--accent);margin-bottom:.6rem;font-weight:600}
.dispute .f p{font-size:.96rem;margin:0}

.note{font-size:.86rem;color:var(--muted);background:var(--paper-2);border:1px solid var(--line-2);
  border-radius:12px;padding:.85rem 1.1rem;margin:1.2rem 0}
.note b{color:var(--ink-soft)}

.figure{margin:1.6rem 0}
.figure img{border-radius:14px;border:1px solid var(--line);box-shadow:var(--shadow-sm)}
.figure figcaption{font-size:.8rem;color:var(--faint);margin-top:.55rem;font-family:var(--mono)}
.float-fig{float:inline-end;width:min(300px,42%);margin:.3rem 0 1.2rem 1.6rem}
.float-fig.start{float:inline-start;margin:.3rem 1.6rem 1.2rem 0}

/* ---- phase-transition demo ---- */
.demo{background:var(--card);border:1px solid var(--line-2);border-radius:var(--r);
  padding:clamp(1.3rem,3vw,2.2rem);box-shadow:var(--shadow-sm);margin:2rem 0}
.demo-grid{display:grid;grid-template-columns:1.1fr .9fr;gap:2rem;align-items:center}
.demo svg{width:100%;height:auto;overflow:visible}
.demo .axis{stroke:var(--line);stroke-width:1.4}
.demo .tick{stroke:var(--line-2);stroke-width:1}
.demo .crisp{fill:none;stroke:var(--faint);stroke-width:2;stroke-dasharray:5 5}
.demo .fuzzy{fill:none;stroke:url(#mg);stroke-width:3.5;stroke-linecap:round}
.demo .marker{fill:var(--c2)}
.demo .lbl{font-family:var(--mono);font-size:11px;fill:var(--muted)}
.slider-row{margin-top:1.2rem}
.slider-row label{font-family:var(--mono);font-size:.8rem;color:var(--muted);display:flex;
  justify-content:space-between;margin-bottom:.5rem}
input[type=range]{width:100%;accent-color:var(--c2);height:6px}
.readout{font-family:var(--mono);margin-top:1rem;font-size:.95rem}
.readout b{color:var(--c2)}
.readout .crispval{color:var(--faint)}
.phasebadge{display:inline-block;font-family:var(--mono);font-size:.78rem;padding:.25rem .6rem;border-radius:999px;
  margin-top:.3rem;border:1px solid var(--line-2)}

.formula{font-family:var(--mono);font-size:clamp(.95rem,1.6vw,1.12rem);background:var(--paper-2);
  border:1px solid var(--line-2);border-radius:12px;padding:1rem 1.2rem;margin:1.4rem 0;color:var(--ink);overflow-x:auto}
.formula .v{color:var(--c2)}

.apps{display:flex;flex-wrap:wrap;gap:.6rem;margin:1.4rem 0}
.chip{display:inline-flex;align-items:center;gap:.45rem;background:var(--card);border:1px solid var(--line-2);
  border-radius:999px;padding:.5rem .95rem;font-size:.88rem;box-shadow:var(--shadow-sm)}
.chip .d{width:8px;height:8px;border-radius:50%;background:var(--grad)}

/* ---- Landau logarithmic scale graphic ---- */
.scale{margin:1.6rem 0;border:1px solid var(--line-2);border-radius:var(--r);background:var(--card);
  padding:1.4rem clamp(1rem,3vw,1.8rem);box-shadow:var(--shadow-sm)}
.scale .bar{position:relative;height:6px;border-radius:3px;background:var(--grad);margin:2.4rem 0 1rem}
.scale .pt{position:absolute;top:50%;transform:translate(-50%,-50%);text-align:center}
.scale .pt .dot{width:13px;height:13px;border-radius:50%;background:#fff;border:3px solid var(--c2);margin:0 auto}
.scale .pt .who{position:absolute;left:50%;transform:translateX(-50%);bottom:18px;white-space:nowrap;
  font-size:.78rem;font-weight:600;color:var(--ink)}
.scale .pt .cls{position:absolute;left:50%;transform:translateX(-50%);top:18px;font-family:var(--mono);
  font-size:.72rem;color:var(--muted)}
.scale .legend{font-size:.82rem;color:var(--muted);margin-top:1.6rem}

.awards{position:relative;margin-top:1rem}
.awards::before{content:"";position:absolute;inset-block:0;inset-inline-start:7px;width:2px;background:var(--grad)}
.award{position:relative;padding-inline-start:2.2rem;padding-block:.7rem}
.award::before{content:"";position:absolute;inset-inline-start:0;inset-block-start:1.15rem;width:16px;height:16px;
  border-radius:50%;background:#fff;border:3px solid var(--c1)}
.award .y{font-family:var(--mono);color:var(--accent);font-weight:600;font-size:.9rem}
.award h4{font-family:var(--sans);font-weight:600;font-size:1.02rem;margin-top:.1rem}
.award p{font-size:.9rem;color:var(--muted);margin-top:.15rem}

.stats{display:grid;grid-template-columns:repeat(4,1fr);gap:1rem;margin:1.5rem 0}
.stat{background:var(--card);border:1px solid var(--line-2);border-radius:14px;padding:1.3rem;text-align:center;box-shadow:var(--shadow-sm)}
.stat b{font-family:var(--serif);font-size:clamp(1.7rem,3vw,2.4rem);display:block;line-height:1;
  background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent}
.stat span{font-size:.82rem;color:var(--muted);display:block;margin-top:.5rem}

.gallery{display:grid;grid-template-columns:repeat(12,1fr);gap:1rem;grid-auto-flow:dense}
.gitem{border-radius:14px;overflow:hidden;border:1px solid var(--line);background:#fff;box-shadow:var(--shadow-sm);position:relative}
.gitem img{width:100%;height:100%;object-fit:cover;transition:transform .5s}
.gitem:hover img{transform:scale(1.04)}
.gitem figcaption{position:absolute;inset-block-end:0;inset-inline:0;padding:1.4rem .9rem .7rem;
  font-size:.8rem;color:#fff;background:linear-gradient(transparent,rgba(0,0,0,.78));line-height:1.35}
.g-tall{grid-column:span 4;grid-row:span 2;min-height:380px}
.g-wide{grid-column:span 8;min-height:240px}
.g-half{grid-column:span 4;min-height:240px}
.g-third{grid-column:span 4;min-height:240px}

footer{background:var(--ink);color:#cdced4;padding-block:clamp(2.5rem,5vw,3.5rem);margin-top:3rem}
footer .wrap{display:grid;grid-template-columns:1.4fr 1fr 1fr;gap:2rem}
footer h4{font-family:var(--mono);font-size:.72rem;letter-spacing:.16em;text-transform:uppercase;color:#83858f;margin-bottom:.9rem;font-weight:600}
footer a{color:#cdced4;font-size:.92rem;display:block;padding:.2rem 0;transition:color .2s}
footer a:hover{color:#fff}
footer .mu{font-family:var(--serif);font-size:2rem;background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent}
footer .lede{color:#9b9ca5;font-size:.95rem;margin-top:.6rem;max-width:34ch}
footer .credit{font-size:.78rem;color:#6c6e78;line-height:1.6}
footer .credit a{display:inline;color:#9b9ca5;text-decoration:underline}
.foot-bottom{border-top:1px solid rgba(255,255,255,.08);margin-top:2rem;padding-top:1.3rem;font-size:.8rem;
  color:#6c6e78;display:flex;justify-content:space-between;flex-wrap:wrap;gap:.6rem}

.reveal{opacity:0;transform:translateY(22px);transition:opacity .7s ease,transform .7s cubic-bezier(.2,.7,.2,1)}
.reveal.in{opacity:1;transform:none}

html[dir=rtl] body{font-family:var(--he)}
html[dir=rtl] h1,html[dir=rtl] h2,html[dir=rtl] h3,html[dir=rtl] h4,
html[dir=rtl] .hero-quote,html[dir=rtl] .pull{font-family:var(--he)}
html[dir=rtl] .mono,html[dir=rtl] .dates,html[dir=rtl] .eyebrow,
html[dir=rtl] .formula,html[dir=rtl] .award .y,html[dir=rtl] .tl b{font-family:var(--mono)}
html[dir=rtl] .portrait-frame::after{transform:scaleX(-1)}

@media(max-width:980px){
  .hero-grid{grid-template-columns:1fr;text-align:center}
  .hero-quote{margin-inline:auto}
  .names-mini{justify-content:center}
  .demo-grid{grid-template-columns:1fr}
  .cards{grid-template-columns:1fr 1fr}
  .tl-strip{grid-template-columns:repeat(3,1fr)}
  .tl-strip .tl:nth-child(4){border-inline-start:0}
  footer .wrap{grid-template-columns:1fr 1fr}
}
@media(max-width:680px){
  .nav{display:none}
  .nav.open{display:flex;position:fixed;inset-block-start:60px;inset-inline:0;flex-direction:column;
    background:var(--paper);padding:1rem;border-bottom:1px solid var(--line);gap:.2rem;z-index:49}
  .nav.open a{padding:.7rem}
  .burger{display:flex}
  .cards{grid-template-columns:1fr}
  .stats{grid-template-columns:1fr 1fr}
  .dispute{grid-template-columns:1fr}
  .tl-strip{grid-template-columns:1fr 1fr}
  .gallery{grid-template-columns:repeat(6,1fr)}
  .g-tall,.g-wide,.g-half,.g-third{grid-column:span 6;grid-row:auto;min-height:230px}
  .float-fig,.float-fig.start{float:none;width:100%;margin-inline:0}
  footer .wrap{grid-template-columns:1fr}
  .btn-row{justify-content:center}
}