*{box-sizing:border-box}
:root{--ink:#172033;--muted:#667085;--brand:#5b4bdb;--brand2:#7c3aed;--bg:#f6f8fc;--card:#fff;--green:#16803c;--greenbg:#e9f9ef;--red:#c62828;--redbg:#fff0f0;--line:#e4e7ec;--shadow:0 12px 35px rgba(31,41,55,.08)}
html{scroll-behavior:smooth}
body{margin:0;font-family:Inter,ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,Arial,sans-serif;background:var(--bg);color:var(--ink);line-height:1.55}
a{color:inherit}
.topbar{position:sticky;top:0;z-index:20;background:rgba(255,255,255,.94);backdrop-filter:blur(12px);border-bottom:1px solid var(--line)}
.brand-wrap{max-width:1180px;margin:auto;padding:12px 18px;display:flex;align-items:center;justify-content:space-between;gap:20px}
.brand{text-decoration:none;font-weight:900;font-size:20px;display:flex;align-items:center;gap:9px}
.brand-mark{width:38px;height:38px;border-radius:12px;display:grid;place-items:center;background:linear-gradient(135deg,var(--brand),var(--brand2));color:#fff;font-size:13px}
.dot{color:var(--brand)}
nav{display:flex;gap:10px;align-items:center;font-weight:800;font-size:13px}
nav a{text-decoration:none}
nav a:hover{color:var(--brand)}
main{max-width:1180px;margin:auto;padding:18px}
.hero{display:grid;grid-template-columns:1.5fr .7fr;gap:18px;margin:10px 0 18px}
.hero-copy,.hero-card{border-radius:28px;padding:30px;background:linear-gradient(135deg,#fff,#f0efff);box-shadow:var(--shadow);border:1px solid #e9e6ff}
.hero-card{display:flex;flex-direction:column;justify-content:center;text-align:center;background:linear-gradient(135deg,#fff,#fff7df)}
.pill{display:inline-block;background:#ebe8ff;color:#4c3ec1;padding:7px 11px;border-radius:999px;font-size:12px;font-weight:900}
h1{font-size:clamp(31px,5vw,54px);line-height:1.05;margin:14px 0 12px;letter-spacing:-1.7px}
.hero p{max-width:700px;color:var(--muted);font-size:17px}
.hero-icons{display:flex;gap:9px;font-size:32px;margin-top:15px}
.big-number{font-size:64px;font-weight:1000;line-height:1;color:var(--brand)}
.hero-card small{display:block;color:var(--muted);margin-top:10px}
.panel{background:var(--card);border:1px solid var(--line);box-shadow:var(--shadow);border-radius:22px;padding:22px;margin-bottom:18px}
.section-title{display:flex;gap:12px;align-items:flex-start}
.section-title>span{font-size:27px}
.section-title h2{margin:0;font-size:22px}
.section-title p{margin:2px 0;color:var(--muted);font-size:14px}
.control-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:12px;margin-top:18px}
label{font-weight:800;font-size:13px;color:#344054}
input,select{width:100%;margin-top:7px;border:1px solid #cfd4dc;border-radius:12px;padding:12px 13px;background:#fff;color:var(--ink);font:inherit;font-size:16px;outline:none}
input:focus,select:focus{border-color:var(--brand);box-shadow:0 0 0 3px #ebe8ff}
.button-row{display:flex;flex-wrap:wrap;gap:10px;margin-top:16px}
.btn{border:0;border-radius:12px;padding:11px 15px;font-weight:900;cursor:pointer;font-size:14px;transition:.18s transform,.18s box-shadow}
.btn:hover{transform:translateY(-1px)}
.primary{background:linear-gradient(135deg,var(--brand),var(--brand2));color:#fff;box-shadow:0 7px 18px rgba(91,75,219,.25)}
.secondary{background:#111827;color:#fff}
.ghost{background:#fff;border:1px solid var(--line);color:var(--ink)}
.notice{margin-top:13px;padding:10px 12px;border-radius:12px;background:#f8fafc;color:var(--muted);font-size:13px}
.sticky-progress{position:sticky;top:63px;z-index:10}
.progress-head{display:flex;gap:14px;align-items:center;justify-content:space-between;font-size:14px}
.progress-track{height:12px;background:#edf0f5;border-radius:999px;overflow:hidden;margin-top:10px}
#progressBar{height:100%;width:0;background:linear-gradient(90deg,var(--brand),#22c55e);border-radius:999px;transition:width .3s}
.timer-line{display:flex;justify-content:space-between;margin-top:8px;font-size:12px;color:var(--muted)}
.worksheet{display:grid;gap:13px}
.qcard{background:#fff;border:1px solid var(--line);border-radius:18px;padding:17px;box-shadow:0 6px 18px rgba(31,41,55,.05);position:relative;overflow:hidden}
.qhead{display:flex;justify-content:space-between;gap:10px;align-items:center}
.qnumber{font-weight:1000;color:var(--brand)}
.badge{font-size:11px;font-weight:900;border-radius:999px;padding:5px 8px;background:#f1f5f9;color:#475467}
.question{font-size:17px;font-weight:800;margin:10px 0 13px}
.answer-row{display:flex;gap:9px}
.answer-row input{margin:0;min-width:0}
.check{white-space:nowrap}
.feedback{min-height:21px;margin-top:8px;font-size:13px;font-weight:800}
.correct{border-color:#73d394!important;background:var(--greenbg)!important;animation:pop .35s ease}
.correct input{border-color:#43a65f!important;background:#f7fff9!important;color:var(--green)}
.wrong{border-color:#ef8a8a!important;background:var(--redbg)!important;animation:shake .35s ease}
.wrong input{border-color:#db5d5d!important;background:#fff8f8!important;color:var(--red)}
.answer{display:none;margin-top:8px;padding:9px 11px;background:#f8fafc;border-radius:10px;color:#344054;font-size:13px}
.answer.show{display:block}
.show-answer{display:none;margin-top:8px}
.show-answer.visible{display:inline-block}
.qcard.checked .show-answer{display:inline-block}
.qcard.checked .show-answer[disabled]{display:none}
.result{text-align:center}
.result-icon{font-size:45px}
.result-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:10px;margin:18px 0}
.result-grid div{background:#f8fafc;border-radius:14px;padding:14px}
.result-grid strong{display:block;font-size:28px;color:var(--brand)}
.result-grid span{color:var(--muted);font-size:12px;font-weight:800}
.hidden{display:none}
.content article{font-size:15px;color:#344054}
.content h3{color:var(--ink);margin-top:25px}
mark{background:#fff0a8;padding:2px 5px;border-radius:5px}
.formula-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:10px}
.formula-grid div{padding:14px;border:1px solid #e8eaf0;border-radius:14px;background:#fbfcfe}
.formula-grid b{display:block;font-size:12px;color:var(--muted)}
.formula-grid span{display:block;margin-top:5px;font-weight:1000;color:var(--brand);font-size:18px}
footer{text-align:center;padding:28px 18px;color:var(--muted);font-size:13px}
@keyframes pop{0%{transform:scale(1)}50%{transform:scale(1.015)}100%{transform:scale(1)}}
@keyframes shake{0%,100%{transform:translateX(0)}25%{transform:translateX(-4px)}75%{transform:translateX(4px)}}
@media(max-width:850px){.hero{grid-template-columns:1fr}.control-grid{grid-template-columns:repeat(2,1fr)}.formula-grid{grid-template-columns:repeat(2,1fr)}}
@media(max-width:560px){main{padding:10px}.brand-wrap{padding:10px 12px}.brand{font-size:17px}.brand-mark{width:34px;height:34px}nav{font-size:11px}.hero-copy,.hero-card{padding:22px;border-radius:20px}.panel{padding:15px;border-radius:18px}.control-grid{grid-template-columns:1fr}.sticky-progress{top:55px}.progress-head{font-size:12px;gap:7px}.timer-line{font-size:11px}.answer-row{flex-direction:column}.check{width:100%}.result-grid{grid-template-columns:repeat(2,1fr)}.formula-grid{grid-template-columns:1fr}.question{font-size:16px}}
@media print{
  body{background:#fff}.topbar,.controls,.sticky-progress,.result,footer{display:none!important}
  main{max-width:none;padding:0}.hero{display:block;box-shadow:none}.hero-card{display:none}.hero-copy{box-shadow:none;padding:10px;border:0;background:#fff}
  .worksheet{display:block}.qcard{box-shadow:none;break-inside:avoid;margin-bottom:10px}.qcard .answer,.qcard .feedback,.qcard .show-answer,.qcard button{display:none!important}
  .qcard input{border:0;border-bottom:1px solid #111;border-radius:0}
  .content{display:none}.question{font-size:13px}.qcard{padding:10px}
}