/* ============================================================
   probsolver.com — Ankun Yu
   Static, dependency-free. Edit freely.
   ============================================================ */

:root{
  --bg:#0a0e13;
  --bg-alt:#0e141b;
  --surface:#121a23;
  --surface-2:#16202b;
  --line:#1e2a37;
  --line-soft:#182430;
  --text:#dbe5ef;
  --text-dim:#8fa2b5;
  --text-mute:#63788c;
  --accent:#4ade80;
  --accent-dim:#2fa963;
  --cyan:#38bdf8;
  --amber:#fbbf24;
  --mono:"JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --sans:"Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --wrap:1120px;
  --r:10px;
}

*,*::before,*::after{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:80px;-webkit-text-size-adjust:100%}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}}

body{
  margin:0;
  background:var(--bg);
  color:var(--text);
  font-family:var(--sans);
  font-size:16.5px;
  line-height:1.65;
  -webkit-font-smoothing:antialiased;
}

img{max-width:100%}
a{color:var(--accent);text-decoration:none}
a:hover{text-decoration:underline}
strong{color:#fff;font-weight:600}

.wrap{max-width:var(--wrap);margin:0 auto;padding:0 24px}

.skip{position:absolute;left:-9999px;top:0;background:var(--accent);color:#062;padding:10px 16px;z-index:100}
.skip:focus{left:8px;top:8px}

:focus-visible{outline:2px solid var(--accent);outline-offset:3px;border-radius:4px}

/* ── NAV ─────────────────────────────────────────── */
.nav{
  position:sticky;top:0;z-index:50;
  background:rgba(10,14,19,.72);
  backdrop-filter:blur(12px);
  -webkit-backdrop-filter:blur(12px);
  border-bottom:1px solid transparent;
  transition:border-color .25s, background .25s;
}
.nav.is-stuck{border-bottom-color:var(--line);background:rgba(10,14,19,.92)}
.nav__inner{display:flex;align-items:center;justify-content:space-between;height:64px;gap:16px}

.brand{
  font-family:var(--mono);font-size:15px;font-weight:700;
  color:var(--text);letter-spacing:-.01em;text-decoration:none;white-space:nowrap;
}
.brand:hover{text-decoration:none;color:#fff}
.brand__prompt{color:var(--accent)}
.brand__caret{color:var(--accent);animation:blink 1.15s step-end infinite}
@keyframes blink{0%,100%{opacity:1}50%{opacity:0}}

.nav__links{display:flex;gap:4px;list-style:none;margin:0;padding:0}
.nav__links a{
  display:block;padding:7px 13px;border-radius:7px;
  font-family:var(--mono);font-size:13.5px;color:var(--text-dim);
  transition:color .18s, background .18s;
}
.nav__links a:hover{color:var(--text);background:var(--surface);text-decoration:none}
.nav__links a.is-active{color:var(--accent);background:rgba(74,222,128,.09)}

.nav__toggle{display:none;background:none;border:0;padding:8px;cursor:pointer;flex-direction:column;gap:5px}
.nav__toggle span{display:block;width:22px;height:2px;background:var(--text);border-radius:2px;transition:transform .25s,opacity .2s}
.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{position:relative;overflow:hidden;padding:clamp(56px,9vw,104px) 0 clamp(64px,10vw,112px)}
.hero__grid{
  position:absolute;inset:0;pointer-events:none;
  background-image:
    linear-gradient(var(--line-soft) 1px, transparent 1px),
    linear-gradient(90deg, var(--line-soft) 1px, transparent 1px);
  background-size:56px 56px;
  mask-image:radial-gradient(ellipse 78% 62% at 50% 0%, #000 12%, transparent 72%);
  -webkit-mask-image:radial-gradient(ellipse 78% 62% at 50% 0%, #000 12%, transparent 72%);
  opacity:.75;
}
.hero__inner{position:relative;display:grid;grid-template-columns:1.05fr .95fr;gap:56px;align-items:center}

.eyebrow{
  font-family:var(--mono);font-size:12.5px;letter-spacing:.09em;text-transform:uppercase;
  color:var(--accent);margin:0 0 18px;
}
.hero h1{
  margin:0;font-size:clamp(46px,7.4vw,78px);line-height:1.02;letter-spacing:-.035em;
  font-weight:700;color:#fff;
}
.hero__role{
  margin:16px 0 0;font-family:var(--mono);font-size:clamp(15px,2vw,18.5px);
  color:var(--cyan);font-weight:500;
}
.hero__role .sep{color:var(--text-mute);margin:0 6px}
.hero__lede{margin:22px 0 0;font-size:17.5px;color:var(--text-dim);max-width:54ch}

.hero__cta{display:flex;flex-wrap:wrap;gap:12px;margin-top:30px}
.btn{
  display:inline-block;padding:11px 22px;border-radius:8px;
  border:1px solid var(--line);background:var(--surface);color:var(--text);
  font-family:var(--mono);font-size:13.5px;font-weight:500;
  transition:border-color .2s, background .2s, transform .2s, color .2s;
}
.btn:hover{text-decoration:none;border-color:var(--text-mute);background:var(--surface-2);transform:translateY(-2px)}
.btn--primary{background:var(--accent);border-color:var(--accent);color:#04250f;font-weight:700}
.btn--primary:hover{background:#5cf090;border-color:#5cf090;color:#04250f}

.hero__stats{display:flex;flex-wrap:wrap;gap:34px;list-style:none;margin:40px 0 0;padding:0}
.hero__stats li{display:flex;flex-direction:column}
.hero__stats b{font-family:var(--mono);font-size:26px;color:#fff;line-height:1.15}
.hero__stats span{font-size:13px;color:var(--text-mute)}

/* terminal */
.term{
  background:var(--surface);border:1px solid var(--line);border-radius:12px;
  overflow:hidden;box-shadow:0 24px 60px -24px rgba(0,0,0,.85);
}
.term__bar{
  display:flex;align-items:center;gap:7px;padding:11px 14px;
  background:var(--surface-2);border-bottom:1px solid var(--line);
}
.term__bar i{width:11px;height:11px;border-radius:50%;background:#2c3a49}
.term__bar i:nth-child(1){background:#ff5f57}
.term__bar i:nth-child(2){background:#febc2e}
.term__bar i:nth-child(3){background:#28c840}
.term__bar span{
  margin-left:10px;font-family:var(--mono);font-size:11.5px;color:var(--text-mute);
  overflow:hidden;text-overflow:ellipsis;white-space:nowrap;
}
.term__body{
  margin:0;padding:20px 20px 24px;
  font-family:var(--mono);font-size:13px;line-height:1.85;
  color:var(--text-dim);overflow-x:auto;
}
.term__body code{font-family:inherit}
.c-dim{color:var(--accent)}
.c-out{color:var(--text)}
.c-key{color:#c084fc}
.c-cls{color:var(--amber)}
.c-fn{color:var(--cyan)}
.c-str{color:#fca5a5}
.cursor{display:inline-block;width:8px;height:15px;background:var(--accent);vertical-align:-2px;animation:blink 1.15s step-end infinite}

/* ── SECTIONS ────────────────────────────────────── */
.section{padding:clamp(64px,9vw,104px) 0;border-top:1px solid var(--line-soft)}
.section--alt{background:var(--bg-alt)}

.h2{
  display:flex;align-items:baseline;gap:14px;margin:0 0 8px;
  font-size:clamp(26px,3.6vw,34px);letter-spacing:-.025em;color:#fff;font-weight:700;
}
.h2__num{font-family:var(--mono);font-size:14px;color:var(--accent);font-weight:500}
.section__sub{margin:0 0 40px;color:var(--text-mute);font-size:15px}
.lead{font-size:18px;color:var(--text);margin-top:0}

/* about */
.about{display:grid;grid-template-columns:1.55fr 1fr;gap:48px;margin-top:32px}
.about__main p{color:var(--text-dim);margin:0 0 18px}
.about__main p:last-child{margin-bottom:0}
.about__side{
  background:var(--surface);border:1px solid var(--line);border-radius:var(--r);
  padding:24px 26px;align-self:start;
}
.about__side h3{
  margin:0 0 18px;font-family:var(--mono);font-size:12px;letter-spacing:.1em;
  text-transform:uppercase;color:var(--accent);font-weight:500;
}
.about__side dl{margin:0;display:grid;grid-template-columns:auto;gap:0}
.about__side dt{
  font-family:var(--mono);font-size:11.5px;letter-spacing:.05em;
  text-transform:uppercase;color:var(--text-mute);margin-top:14px;
}
.about__side dt:first-child{margin-top:0}
.about__side dd{margin:2px 0 0;font-size:14.5px;color:var(--text)}

/* stack */
.stack{display:grid;grid-template-columns:repeat(auto-fit,minmax(248px,1fr));gap:16px}
.card{
  background:var(--surface);border:1px solid var(--line);border-radius:var(--r);
  padding:22px 22px 20px;transition:border-color .22s, transform .22s;
}
.card:hover{border-color:#2c3d4e;transform:translateY(-3px)}
.card h3{
  display:flex;align-items:center;gap:10px;margin:0 0 16px;
  font-size:15px;font-weight:600;color:#fff;
}
.card__ico{
  display:inline-flex;align-items:center;justify-content:center;
  width:28px;height:28px;border-radius:7px;flex:none;
  background:rgba(74,222,128,.1);border:1px solid rgba(74,222,128,.22);
  font-family:var(--mono);font-size:12px;color:var(--accent);
}
.chips{display:flex;flex-wrap:wrap;gap:7px;list-style:none;margin:0;padding:0}
.chip{
  font-family:var(--mono);font-size:12px;padding:5px 10px;border-radius:6px;
  background:var(--surface-2);border:1px solid var(--line);color:var(--text-dim);
}
.chip--hot{
  background:rgba(74,222,128,.09);border-color:rgba(74,222,128,.3);
  color:var(--accent);font-weight:500;
}

/* timeline */
.tl{list-style:none;margin:0;padding:0;position:relative}
.tl__item{position:relative;display:grid;grid-template-columns:150px 1fr;gap:32px;padding-bottom:34px}
.tl__item::before{
  content:"";position:absolute;left:150px;top:12px;bottom:-12px;width:1px;
  background:var(--line);transform:translateX(15px);
}
.tl__item:last-child::before{display:none}
.tl__item::after{
  content:"";position:absolute;left:150px;top:9px;width:9px;height:9px;border-radius:50%;
  background:var(--line);border:2px solid var(--bg);transform:translateX(11px);box-sizing:content-box;
}
.tl__item--now::after{background:var(--accent);box-shadow:0 0 0 4px rgba(74,222,128,.14)}
.tl__when{
  font-family:var(--mono);font-size:13px;color:var(--text-mute);
  text-align:right;padding-top:4px;white-space:nowrap;
}
.tl__item--now .tl__when{color:var(--accent)}
.tl__card{
  background:var(--surface);border:1px solid var(--line);border-radius:var(--r);
  padding:22px 24px;transition:border-color .22s;
}
.tl__card:hover{border-color:#2c3d4e}
.tl__role{margin:0;font-size:18px;font-weight:600;color:#fff;letter-spacing:-.01em}
.tl__org{margin:4px 0 14px;font-family:var(--mono);font-size:13.5px;color:var(--cyan)}
.tl__loc{color:var(--text-mute)}
.tl__card ul{margin:0;padding-left:19px;color:var(--text-dim)}
.tl__card ul li{margin-bottom:8px;font-size:15.3px}
.tl__card ul li:last-child{margin-bottom:0}
.tags{display:flex;flex-wrap:wrap;gap:6px;list-style:none;margin:16px 0 0!important;padding:0!important}
.tags li{
  font-family:var(--mono);font-size:11px;padding:3px 8px;border-radius:5px;
  background:var(--bg-alt);border:1px solid var(--line);color:var(--text-mute);margin:0!important;
}

/* contact */
.contact{max-width:620px}
.contact__links{list-style:none;margin:28px 0 0;padding:0;display:grid;gap:9px}
.contact__links a{
  display:flex;align-items:center;gap:16px;padding:14px 18px;
  background:var(--surface);border:1px solid var(--line);border-radius:var(--r);
  color:var(--text);font-family:var(--mono);font-size:14px;
  transition:border-color .2s, transform .2s, background .2s;
}
.contact__links a:hover{text-decoration:none;border-color:var(--accent);transform:translateX(4px);background:var(--surface-2)}
.contact__links .k{color:var(--accent);width:78px;flex:none;font-size:12.5px}
.contact__links .v{color:var(--text-dim);word-break:break-all}
.contact__links a:hover .v{color:var(--text)}

/* footer */
.foot{border-top:1px solid var(--line-soft);padding:28px 0;background:var(--bg)}
.foot__inner{display:flex;flex-wrap:wrap;gap:8px;justify-content:space-between;align-items:center}
.foot p{margin:0;font-family:var(--mono);font-size:12.5px;color:var(--text-mute)}

/* reveal */
.reveal{opacity:0;transform:translateY(16px)}
.reveal.is-in{opacity:1;transform:none;transition:opacity .6s ease, transform .6s cubic-bezier(.2,.7,.3,1)}
@media (prefers-reduced-motion:reduce){
  .reveal,.reveal.is-in{opacity:1;transform:none;transition:none}
  .brand__caret,.cursor{animation:none}
}

/* ── RESPONSIVE ──────────────────────────────────── */
@media (max-width:940px){
  .hero__inner{grid-template-columns:1fr;gap:44px}
  .about{grid-template-columns:1fr;gap:32px}
}
@media (max-width:720px){
  body{font-size:16px}
  .nav__toggle{display:flex}
  .nav__links{
    position:absolute;top:64px;left:0;right:0;
    flex-direction:column;gap:0;padding:8px;
    background:rgba(10,14,19,.98);border-bottom:1px solid var(--line);
    display:none;
  }
  .nav__links.is-open{display:flex}
  .nav__links a{padding:12px 14px;font-size:14.5px}

  .tl__item{grid-template-columns:1fr;gap:10px;padding-left:26px;padding-bottom:26px}
  .tl__item::before{left:0;transform:none;top:26px;bottom:-6px}
  .tl__item::after{left:0;top:22px;transform:translateX(-4px)}
  .tl__when{text-align:left;padding-top:0}
  .tl__card{padding:18px 18px}
  .hero__stats{display:grid;grid-template-columns:repeat(3,1fr);gap:14px}
  .hero__stats b{font-size:22px}
  .hero__stats span{font-size:12px;line-height:1.35}
  .contact__links a{flex-direction:column;align-items:flex-start;gap:4px}
  .contact__links .k{width:auto}
}

/* ── PRINT (reads as a one-page resume) ──────────── */
@media print{
  :root{--text:#111;--text-dim:#333;--text-mute:#666}
  body{background:#fff;color:#111;font-size:10.5pt}
  .nav,.hero__grid,.term,.hero__cta,.nav__toggle,.skip,.foot__meta,.section__sub{display:none!important}
  .section,.hero{padding:14pt 0;border:0;background:#fff!important}
  .wrap{max-width:none;padding:0}
  .h2{color:#000;font-size:15pt}
  .h2__num{color:#666}
  .hero h1{font-size:26pt;color:#000}
  .hero__role{color:#333}
  strong,.tl__role,.card h3,.hero__stats b,.about__side dd,.lead{color:#000!important}
  .foot{background:#fff!important;border-top:1px solid #ccc}
  .foot p{color:#666}
  .hero__stats{gap:18pt}
  .hero__stats b{font-size:14pt}
  .card,.tl__card,.about__side,.contact__links a{
    background:#fff!important;border:1px solid #ccc!important;box-shadow:none!important;
  }
  .tl__item{break-inside:avoid;page-break-inside:avoid;padding-bottom:10pt}
  .chip,.tags li{background:#f4f4f4!important;color:#333!important;border-color:#ddd!important}
  a{color:#111!important;text-decoration:none!important}
  .reveal{opacity:1!important;transform:none!important}
}