:root{
  --bg:#FCFCFB; --surface:#FFFFFF; --ink:#15181D; --muted:#5A6068; --line:#E6E5E0;
  --amber:#B26A00; --amber-soft:#FFF4E0; --blue:#2563D6; --dark:#111214; --amber-bright:#FFB000;
  --radius:16px; --shadow:0 1px 2px rgba(20,22,26,.06),0 8px 24px rgba(20,22,26,.05);
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--ink);
  font-family:"Source Sans 3",system-ui,-apple-system,Segoe UI,Arial,sans-serif;font-size:18px;line-height:1.65}
h1,h2,h3,.brand{font-family:Poppins,system-ui,sans-serif;line-height:1.2;letter-spacing:-.01em}
h1{font-size:clamp(2rem,5.2vw,3.1rem);margin:0 0 14px;font-weight:700}
h2{font-size:clamp(1.4rem,3.2vw,1.9rem);margin:48px 0 14px;font-weight:700}
h3{font-size:1.15rem;margin:28px 0 8px;font-weight:600}
p{margin:0 0 16px}
a{color:var(--amber);text-decoration:none;border-bottom:1px solid rgba(178,106,0,.3)}
a:hover{border-bottom-color:var(--amber)}
.wrap{max-width:820px;margin:0 auto;padding:0 20px}
.wrap-wide{max-width:1060px;margin:0 auto;padding:0 20px}
/* header */
header{background:var(--dark);position:sticky;top:0;z-index:20}
.nav{display:flex;align-items:center;gap:14px;padding:12px 0}
.nav img{height:34px;width:34px;border-radius:50%}
.nav .brand{color:#fff;font-weight:700;font-size:.98rem;letter-spacing:.06em}
.nav .links{margin-left:auto;display:flex;gap:16px;font-size:.92rem;flex-wrap:wrap}
.nav .links a{color:#d9d9d6;border:0}
.nav .links a:hover,.nav .links a[aria-current=page]{color:var(--amber-bright)}
/* hero band */
.hero{background:var(--dark);color:#fff;padding:52px 0 60px}
.hero h1{color:#fff}
.hero .lede{color:#c9c9c5;font-size:1.12rem;max-width:620px;margin:0}
.hero .amb{color:var(--amber-bright)}
.btn{display:inline-block;background:var(--amber-bright);color:#111;border:0;border-radius:999px;
  padding:12px 22px;font-weight:600;font-size:1rem;cursor:pointer;font-family:inherit;margin:18px 10px 0 0}
.btn:hover{filter:brightness(1.06);border:0}
.btn.ghost{background:transparent;color:#fff;box-shadow:inset 0 0 0 1px #4a4c50}
.btn.solid{background:var(--amber);color:#fff}
/* cards */
.card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:24px;box-shadow:var(--shadow);margin:20px 0}
.grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(250px,1fr));gap:18px}
.tool{display:block;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);
  padding:22px;color:var(--ink);box-shadow:var(--shadow)}
.tool:hover{border-color:var(--amber);transform:translateY(-2px);transition:.15s}
.tool b{display:block;font-family:Poppins,sans-serif;font-size:1.05rem;margin-bottom:6px}
.tool span{color:var(--muted);font-size:.95rem}
.kicker{font-size:.78rem;letter-spacing:.14em;text-transform:uppercase;color:var(--muted);margin-bottom:6px}
.big{font-family:Poppins,sans-serif;font-weight:700;color:var(--amber);font-size:clamp(2.4rem,9vw,3.6rem);line-height:1.05}
.muted{color:var(--muted)}
.small{font-size:.92rem}
/* controls */
input[type=range]{width:100%;accent-color:var(--amber);height:32px}
input[type=number],select{padding:10px 12px;border:1px solid var(--line);border-radius:10px;font-size:1rem;
  font-family:inherit;background:var(--surface);color:var(--ink);width:110px}
label{font-size:.9rem;color:var(--muted);display:block;margin-bottom:4px}
.row{display:flex;gap:18px;flex-wrap:wrap;align-items:flex-end}
.bar{height:14px;border-radius:999px;background:#EDEDE8;overflow:hidden}
.bar>i{display:block;height:100%;background:var(--amber);width:0;transition:width .2s}
table{width:100%;border-collapse:collapse;margin:14px 0}
th,td{border-bottom:1px solid var(--line);padding:10px 6px;text-align:left;font-size:.97rem}
th{color:var(--muted);font-weight:600;font-size:.85rem;letter-spacing:.04em;text-transform:uppercase}
.formula{background:#F6F6F2;border:1px solid var(--line);border-radius:12px;padding:14px 16px;overflow-x:auto;
  font-family:ui-monospace,Menlo,Consolas,monospace;font-size:.95rem}
.note{background:var(--amber-soft);border-left:3px solid var(--amber);border-radius:0 10px 10px 0;padding:12px 16px;margin:18px 0}
/* video */
.videos{background:var(--dark);padding:44px 0 50px;margin-top:56px;color:#fff}
.videos h2{color:#fff;margin-top:0}
.video{position:relative;padding-top:177.8%;border-radius:14px;overflow:hidden;background:#000}
.video iframe{position:absolute;inset:0;width:100%;height:100%;border:0}
.vcap{color:#bdbdb9;font-size:.9rem;text-align:center;margin:10px 0 0}
/* doors */
.doors{display:grid;grid-template-columns:repeat(3,1fr);gap:14px;max-width:460px;margin:18px auto}
.door{aspect-ratio:3/4.4;border:2px solid var(--ink);border-radius:12px;background:var(--surface);
  font-family:Poppins,sans-serif;font-size:1.6rem;font-weight:700;cursor:pointer;display:flex;align-items:center;
  justify-content:center;flex-direction:column;gap:6px;color:var(--ink);transition:.15s}
.door small{font-size:.7rem;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);font-family:inherit}
.door:hover:not(:disabled){border-color:var(--amber)}
.door.picked{border-color:var(--amber);background:var(--amber-soft)}
.door.open{background:#F2F2EE;color:var(--muted);border-style:dashed}
.door:disabled{cursor:default}
.tally{display:grid;grid-template-columns:1fr 1fr;gap:14px;margin-top:18px}
.stat{background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:14px}
.stat b{font-family:Poppins,sans-serif;font-size:1.6rem;display:block}
footer{border-top:1px solid var(--line);margin-top:60px;padding:28px 0 40px;color:var(--muted);font-size:.92rem}
footer a{color:var(--muted)}
.chart-wrap{position:relative}
.tip{position:absolute;pointer-events:none;background:var(--ink);color:#fff;font-size:.82rem;padding:6px 9px;
  border-radius:8px;transform:translate(-50%,-140%);white-space:nowrap;opacity:0;transition:opacity .1s}
@media (max-width:520px){body{font-size:17px}.nav .links{gap:12px;font-size:.86rem}}

.guess{background:#1b1c1f;border:1px solid #2c2e32;border-radius:18px;padding:22px;margin-top:26px;max-width:640px}
.guess .q{color:#efefec;font-size:1.06rem;margin:6px 0 16px}
.guess .q strong{color:var(--amber-bright)}
.guess input{width:150px;background:#101113;border-color:#34363a;color:#fff}
.guess .ans{display:none;margin-top:16px;padding-top:16px;border-top:1px solid #2c2e32;color:#d7d7d3}
.guess .ans b{color:var(--amber-bright);font-family:Poppins,sans-serif;font-size:1.5rem;display:block;margin-bottom:4px}
.guess .ans a{color:var(--amber-bright)}