/* USMLE Step 1 QBank — design system. Charcoal + cyan/teal + coral. Mobile-first. */
@font-face{font-family:"Plus Jakarta Sans";src:url(/fonts/plus-jakarta-sans.woff2) format("woff2");font-weight:200 800;font-display:swap}
@font-face{font-family:"IBM Plex Mono";src:url(/fonts/ibm-plex-mono-500.woff2) format("woff2");font-weight:500;font-display:swap}
:root{--ink:#111827;--ink-2:#374151;--muted:#6B7280;--line:#E5E7EB;--panel:#F1F5F9;--bg:#FFFFFF;--card:#FFFFFF;
--cyan:#06B6D4;--teal:#0891B2;--teal-d:#0E7490;--cyan-50:#ECFEFF;--coral:#FB7185;--coral-d:#E11D48;--coral-50:#FFF1F2;--ok:#059669;--ok-50:#ECFDF5;
--r:14px;--r-lg:22px;--sh:0 1px 2px rgba(17,24,39,.06),0 8px 24px rgba(17,24,39,.06);--fs:1rem}
html[data-theme=dark]{--ink:#F3F4F6;--ink-2:#D1D5DB;--muted:#9CA3AF;--line:#2B3442;--panel:#1A2230;--bg:#0B0F17;--card:#121826;--cyan-50:#0B2A33;--coral-50:#3A1520;--ok-50:#0B2C22}
html[data-fs=lg]{--fs:1.125rem}html[data-fs=xl]{--fs:1.25rem}
*{box-sizing:border-box}html{-webkit-text-size-adjust:100%}
body{margin:0;font-family:"Plus Jakarta Sans",system-ui,-apple-system,"Segoe UI",sans-serif;font-size:var(--fs);line-height:1.6;color:var(--ink);background:var(--bg)}
a{color:var(--teal);text-underline-offset:3px}a:hover{color:var(--teal-d)}
html[data-theme=dark] a{color:#22D3EE}
img,svg{max-width:100%}
h1,h2,h3{line-height:1.2;letter-spacing:-.02em;margin:0 0 .5em}
h1{font-size:clamp(1.9rem,6vw,3.1rem);font-weight:800}h2{font-size:clamp(1.45rem,4vw,2.1rem);font-weight:800}h3{font-size:1.15rem;font-weight:700}
p{margin:0 0 1em}.mono{font-family:"IBM Plex Mono",ui-monospace,monospace}
.wrap{width:100%;max-width:1120px;margin:0 auto;padding:0 18px}.narrow{max-width:760px}
.skip{position:absolute;left:-999px}.skip:focus{left:12px;top:12px;z-index:99;background:#fff;padding:8px 12px;border-radius:8px}
:focus-visible{outline:3px solid var(--cyan);outline-offset:2px}
/* header */
.hdr{position:sticky;top:0;z-index:40;background:#111827;color:#fff;border-bottom:1px solid #1F2937}
.hdr .wrap{display:flex;align-items:center;gap:12px;height:62px}
.brand{display:flex;align-items:center;gap:10px;color:#fff;text-decoration:none;font-weight:800;letter-spacing:-.01em;white-space:nowrap}
.brand img{width:34px;height:34px}.brand small{display:block;font-weight:500;font-size:.68rem;color:#67E8F9;letter-spacing:.06em;text-transform:uppercase;line-height:1}
.nav{display:none;margin-left:auto;gap:4px;align-items:center}
.nav a{color:#E5E7EB;text-decoration:none;padding:8px 12px;border-radius:10px;font-weight:600;font-size:.93rem}
.nav a:hover,.nav a[aria-current=page]{background:#1F2937;color:#fff}
.menu-btn{margin-left:auto;background:none;border:1px solid #374151;color:#fff;border-radius:10px;padding:8px 12px;font:inherit;font-weight:700}
.mnav{display:none;background:#111827;border-top:1px solid #1F2937;padding:8px 18px 16px}
.mnav.open{display:block}.mnav a{display:block;color:#E5E7EB;padding:12px 4px;text-decoration:none;font-weight:600;border-bottom:1px solid #1F2937}
@media(min-width:960px){.nav{display:flex}.menu-btn,.mnav{display:none!important}}
/* buttons */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;min-height:46px;padding:10px 20px;border-radius:12px;border:2px solid transparent;font:inherit;font-weight:700;text-decoration:none;cursor:pointer;transition:.15s;line-height:1.2}
.btn-primary{background:var(--teal);color:#fff!important}.btn-primary:hover{background:var(--teal-d)}
.btn-light{background:#fff;color:#111827!important;border-color:var(--line)}.btn-light:hover{border-color:var(--teal)}
.btn-ghost{background:transparent;color:inherit!important;border-color:currentColor}
.btn-coral{background:var(--coral);color:#111827!important}.btn-sm{min-height:38px;padding:6px 14px;font-size:.9rem}
.btn-block{width:100%}.btn[disabled]{opacity:.5;cursor:not-allowed}
.nav .btn{padding:8px 14px;min-height:38px}
/* sections */
.section{padding:56px 0}.section.alt{background:var(--panel)}
.eyebrow{display:inline-block;font-size:.78rem;font-weight:800;letter-spacing:.08em;text-transform:uppercase;color:var(--teal);margin-bottom:10px}
.lead{font-size:1.12rem;color:var(--ink-2)}
.hero{background:radial-gradient(1200px 500px at 85% -10%,rgba(6,182,212,.25),transparent 60%),#111827;color:#fff;padding:44px 0 56px}
.hero .lead{color:#D1D5DB}.hero h1 span{color:#22D3EE}
.hero-grid{display:grid;gap:28px}@media(min-width:960px){.hero-grid{grid-template-columns:1.05fr 1fr;align-items:center;gap:44px}}
.chips{display:flex;flex-wrap:wrap;gap:8px;margin:18px 0 22px}.chip{font-size:.85rem;font-weight:600;padding:6px 12px;border-radius:999px;background:rgba(255,255,255,.08);border:1px solid rgba(255,255,255,.14)}
.cta-row{display:flex;flex-wrap:wrap;gap:10px}
.grid{display:grid;gap:16px}@media(min-width:720px){.g2{grid-template-columns:repeat(2,1fr)}.g3{grid-template-columns:repeat(3,1fr)}.g4{grid-template-columns:repeat(2,1fr)}}@media(min-width:1040px){.g4{grid-template-columns:repeat(4,1fr)}}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--r-lg);padding:22px;box-shadow:var(--sh)}
.step-n{width:38px;height:38px;border-radius:12px;display:grid;place-items:center;background:var(--cyan-50);color:var(--teal);font-weight:800;margin-bottom:12px}
/* packages */
.pkg{position:relative;display:flex;flex-direction:column}.pkg .price{font-size:2.4rem;font-weight:800;letter-spacing:-.03em}.pkg .price small{font-size:1rem;color:var(--muted);font-weight:600}
.pkg ul{list-style:none;padding:0;margin:14px 0 20px;flex:1}.pkg li{padding:6px 0 6px 26px;position:relative}.pkg li:before{content:"";position:absolute;left:2px;top:12px;width:12px;height:7px;border-left:3px solid var(--teal);border-bottom:3px solid var(--teal);transform:rotate(-45deg)}
.pkg.featured{border:2px solid var(--teal);box-shadow:0 12px 40px rgba(8,145,178,.2)}
.badge{display:inline-block;font-size:.72rem;font-weight:800;letter-spacing:.05em;text-transform:uppercase;padding:4px 10px;border-radius:999px;background:var(--cyan-50);color:var(--teal-d)}
.pkg .badge{position:absolute;top:-12px;right:18px;background:var(--teal);color:#fff}.pkg .badge.alt{background:var(--coral);color:#111827}
.badge.coral{background:var(--coral-50);color:var(--coral-d)}.badge.ok{background:var(--ok-50);color:var(--ok)}.badge.grey{background:var(--panel);color:var(--muted)}
/* question card */
.qcard{background:var(--card);color:var(--ink);border-radius:var(--r-lg);padding:20px;box-shadow:0 20px 50px rgba(0,0,0,.25);border:1px solid var(--line)}
.qmeta{display:flex;flex-wrap:wrap;gap:6px;margin-bottom:12px}
.stem{font-size:1.02em}.leadin{font-weight:700;margin:.4em 0 1em}
.opts{display:grid;gap:10px;margin:0;padding:0;list-style:none}
.opt{display:flex;gap:12px;align-items:flex-start;width:100%;text-align:left;background:var(--card);color:var(--ink);border:2px solid var(--line);border-radius:12px;padding:12px 14px;font:inherit;cursor:pointer;transition:.12s}
.opt:hover{border-color:var(--cyan)}.opt .l{flex:none;width:28px;height:28px;border-radius:8px;display:grid;place-items:center;background:var(--panel);font-weight:800;font-size:.9rem}
.opt input{position:absolute;opacity:0}.opt:has(input:checked){border-color:var(--teal);background:var(--cyan-50)}
.opt:has(input:checked) .l{background:var(--teal);color:#fff}
.opt.correct{border-color:var(--cyan);background:var(--cyan-50)}.opt.correct .l{background:var(--teal);color:#fff}
.opt.wrong{border-color:var(--coral);background:var(--coral-50)}.opt.wrong .l{background:var(--coral);color:#111827}
.opt[disabled]{cursor:default}.opt .note[hidden],[hidden]{display:none!important}.opt .note{display:block;font-size:.9em;color:var(--ink-2);margin-top:4px}
.explain{margin-top:18px;border-top:1px solid var(--line);padding-top:16px}
.explain h3{font-size:1rem;text-transform:uppercase;letter-spacing:.05em;color:var(--teal)}
.takeaway{background:var(--cyan-50);border-left:4px solid var(--cyan);padding:12px 14px;border-radius:10px;font-weight:600}
.result{padding:12px 14px;border-radius:12px;font-weight:700;margin:14px 0}.result.ok{background:var(--cyan-50);color:var(--teal-d)}.result.bad{background:var(--coral-50);color:var(--coral-d)}
html[data-theme=dark] .result.ok{color:#67E8F9}html[data-theme=dark] .result.bad{color:#FDA4AF}
/* forms */
.form{display:grid;gap:16px}.field label{display:block;font-weight:700;margin-bottom:6px;font-size:.95rem}
.field .hint{font-size:.85rem;color:var(--muted);margin-top:4px}
.input,select.input,textarea.input{width:100%;min-height:48px;padding:11px 14px;border:2px solid var(--line);border-radius:12px;font:inherit;background:var(--card);color:var(--ink)}
.input:focus{border-color:var(--cyan);outline:none;box-shadow:0 0 0 4px rgba(6,182,212,.18)}
.input.invalid,.field.has-error .input{border-color:var(--coral)}.err{color:var(--coral-d);font-size:.88rem;font-weight:600;margin-top:5px}
html[data-theme=dark] .err{color:#FDA4AF}
.row2{display:grid;gap:16px}@media(min-width:640px){.row2{grid-template-columns:1fr 1fr}}
.check{display:flex;gap:10px;align-items:flex-start;font-size:.95rem}.check input{width:20px;height:20px;margin-top:3px;accent-color:var(--teal)}
.choice-grid{display:grid;gap:10px;grid-template-columns:repeat(2,1fr)}@media(min-width:720px){.choice-grid.c4{grid-template-columns:repeat(4,1fr)}.choice-grid.c3{grid-template-columns:repeat(3,1fr)}}
.choice{position:relative;display:block;border:2px solid var(--line);border-radius:14px;padding:12px 14px;cursor:pointer;background:var(--card)}
.choice input{position:absolute;opacity:0}.choice:has(input:checked){border-color:var(--teal);background:var(--cyan-50)}
.choice:has(input:focus-visible){outline:3px solid var(--cyan)}.choice b{display:block}.choice span{font-size:.88rem;color:var(--muted)}
.hp{position:absolute;left:-5000px}
.summary-box{position:sticky;top:80px}
.notice{padding:14px 16px;border-radius:12px;background:var(--cyan-50);border:1px solid rgba(6,182,212,.35);margin-bottom:16px}
.notice.warn{background:var(--coral-50);border-color:rgba(251,113,133,.45)}
/* faq */
details{border:1px solid var(--line);border-radius:14px;padding:4px 18px;background:var(--card);margin-bottom:10px}
summary{cursor:pointer;font-weight:700;padding:12px 0;list-style:none;display:flex;justify-content:space-between;gap:10px}
summary::after{content:"+";color:var(--teal);font-weight:800}details[open] summary::after{content:"–"}
/* footer */
.ftr{background:#111827;color:#D1D5DB;padding:44px 0 28px;margin-top:40px;font-size:.93rem}
.ftr a{color:#E5E7EB;text-decoration:none}.ftr a:hover{color:#67E8F9}
.ftr-grid{display:grid;gap:24px}@media(min-width:800px){.ftr-grid{grid-template-columns:1.4fr 1fr 1fr 1fr}}
.ftr h4{color:#fff;margin:0 0 10px;font-size:.95rem}.ftr ul{list-style:none;padding:0;margin:0}.ftr li{padding:4px 0}
.disclaimer{border-top:1px solid #1F2937;margin-top:28px;padding-top:18px;color:#9CA3AF;font-size:.85rem}
/* app shell */
.app-nav{background:var(--card);border-bottom:1px solid var(--line);position:sticky;top:62px;z-index:30}
.app-nav .wrap{display:flex;gap:4px;overflow-x:auto;scrollbar-width:none}
.app-nav a{white-space:nowrap;padding:12px 14px;text-decoration:none;color:var(--ink-2);font-weight:700;font-size:.92rem;border-bottom:3px solid transparent}
.app-nav a[aria-current=page]{color:var(--teal);border-color:var(--cyan)}
.stat{font-size:2rem;font-weight:800;letter-spacing:-.03em}.stat-l{color:var(--muted);font-size:.88rem;font-weight:600}
.bar{height:10px;background:var(--panel);border-radius:99px;overflow:hidden}.bar i{display:block;height:100%;background:linear-gradient(90deg,var(--teal),var(--cyan));border-radius:99px}
.bar.low i{background:var(--coral)}
table.t{width:100%;border-collapse:collapse;font-size:.93rem}.t th,.t td{padding:10px 8px;border-bottom:1px solid var(--line);text-align:left;vertical-align:top}.t th{font-size:.78rem;text-transform:uppercase;letter-spacing:.05em;color:var(--muted)}
.tscroll{overflow-x:auto}
.banner{background:linear-gradient(90deg,#0E7490,#0891B2);color:#fff;padding:10px 0;font-weight:600;font-size:.93rem}
.banner.end{background:#111827;border-bottom:3px solid var(--coral)}.banner a{color:#fff}
.flash{background:var(--ok-50);color:var(--ok);padding:12px 16px;border-radius:12px;font-weight:600;margin:16px 0}
.flash.err-f{background:var(--coral-50);color:var(--coral-d)}
/* practice */
.qbar{display:flex;align-items:center;gap:10px;flex-wrap:wrap;justify-content:space-between;margin:16px 0}
.timer{font-family:"IBM Plex Mono",monospace;font-size:1.1rem;background:#111827;color:#67E8F9;padding:6px 12px;border-radius:10px}
.timer.low{color:var(--coral)}
.qnav{display:flex;gap:6px;flex-wrap:wrap;margin:10px 0 18px}.qnav a{min-width:36px;height:36px;display:grid;place-items:center;border-radius:9px;border:2px solid var(--line);text-decoration:none;color:var(--ink);font-weight:700;font-size:.85rem}
.qnav a.cur{border-color:var(--ink);background:var(--ink);color:var(--bg)}.qnav a.c{border-color:var(--cyan);background:var(--cyan-50)}.qnav a.w{border-color:var(--coral);background:var(--coral-50)}.qnav a.d{border-color:var(--teal)}
.tools{display:flex;gap:8px;flex-wrap:wrap}
.kbd{font-family:"IBM Plex Mono",monospace;font-size:.75rem;border:1px solid var(--line);border-bottom-width:2px;border-radius:6px;padding:1px 6px;background:var(--panel)}
.labs{display:none}.labs.open{display:block}
.prose h2{margin-top:1.6em;font-size:1.35rem}.prose{max-width:760px}.prose li{margin-bottom:.4em}
.muted{color:var(--muted)}.center{text-align:center}.mt0{margin-top:0}.mb0{margin-bottom:0}.mt{margin-top:24px}
.pill-toggle{display:flex;gap:6px}.pill-toggle button{background:none;border:1px solid #374151;color:#E5E7EB;border-radius:8px;padding:4px 8px;font:inherit;font-size:.8rem;cursor:pointer}
@media print{.hdr,.ftr,.app-nav{display:none}}
/* exam tools */
.stem mark,.leadin mark{background:#FDE68A;color:#111827;border-radius:3px;padding:0 1px;cursor:pointer}
body[data-hl-mode="1"] [data-hl]{cursor:text;outline:2px dashed #FDE68A;outline-offset:6px;border-radius:6px}
.calc{display:none;position:fixed;right:16px;bottom:16px;z-index:50;width:260px;background:var(--card);border:1px solid var(--line);border-radius:18px;box-shadow:0 20px 50px rgba(0,0,0,.25);padding:14px}
.calc.open{display:block}.calc input{width:100%;font-family:"IBM Plex Mono",monospace;font-size:1.3rem;text-align:right;padding:10px;border:2px solid var(--line);border-radius:10px;background:var(--panel);color:var(--ink);margin-bottom:10px}
.calc .keys{display:grid;grid-template-columns:repeat(4,1fr);gap:6px}.calc .keys button{min-height:44px;border:1px solid var(--line);border-radius:10px;background:var(--card);color:var(--ink);font:inherit;font-weight:700;cursor:pointer}
.calc .keys button.op{background:var(--cyan-50);color:var(--teal-d)}.calc .keys button.eq{background:var(--teal);color:#fff}