:root{
  --bg:#f6f8fc; --surface:#ffffff; --ink:#172033; --muted:#657086;
  --line:#e6eaf1; --navy:#07111f; --blue:#2563eb; --cyan:#0ea5e9;
  --apolar:#f59e0b; --aromatic:#8b5cf6; --polar:#10b981;
  --positive:#ec4899; --negative:#0ea5e9;
  --shadow:0 18px 50px rgba(15,23,42,.09); --radius:24px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--ink);font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;line-height:1.65}
button,input{font:inherit}
a{color:inherit}
.coursebar{position:sticky;top:0;z-index:50;background:rgba(7,17,31,.94);backdrop-filter:blur(15px);color:white;border-bottom:1px solid rgba(255,255,255,.08)}
.coursebar-inner{width:min(1180px,calc(100% - 32px));height:68px;margin:auto;display:flex;align-items:center;justify-content:space-between;gap:18px}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none;font-weight:850}
.brand-mark{width:36px;height:36px;border-radius:12px;display:grid;place-items:center;background:linear-gradient(135deg,rgba(94,234,212,.18),rgba(96,165,250,.2));border:1px solid rgba(255,255,255,.12)}
.back{text-decoration:none;color:#c6d2e3;font-size:.9rem;font-weight:700;padding:9px 12px;border:1px solid rgba(255,255,255,.11);border-radius:12px}
.back:hover{color:white;background:rgba(255,255,255,.07)}
.shell{width:min(1120px,calc(100% - 32px));margin:auto}
.course-intro{padding:55px 0 28px}
.breadcrumb{font-weight:800;font-size:.78rem;letter-spacing:.1em;text-transform:uppercase;color:var(--blue);margin:0 0 12px}
h1{font-size:clamp(2.5rem,6vw,5rem);line-height:1;letter-spacing:-.055em;margin:0;max-width:880px}
.lead{font-size:1.12rem;color:var(--muted);max-width:780px;margin:20px 0 0}
.progress-card{margin-top:28px;background:white;border:1px solid var(--line);border-radius:18px;padding:16px 18px;display:flex;align-items:center;gap:16px;box-shadow:0 8px 28px rgba(15,23,42,.05)}
.progress-track{height:8px;flex:1;background:#edf1f7;border-radius:999px;overflow:hidden}
.progress-fill{height:100%;width:0;background:linear-gradient(90deg,#38bdf8,#2563eb);border-radius:inherit;transition:.3s}
.progress-text{font-size:.86rem;font-weight:800;color:var(--muted);white-space:nowrap}
.module-nav{display:grid;grid-template-columns:repeat(4,1fr);gap:10px;margin:26px 0 46px}
.module-link{text-decoration:none;background:white;border:1px solid var(--line);border-radius:15px;padding:12px 13px;font-weight:800;font-size:.84rem;color:#4a5568;transition:.2s}
.module-link:hover{transform:translateY(-2px);border-color:#b9c8e5;color:var(--blue)}
.module-link small{display:block;color:#94a3b8;font-size:.7rem;margin-bottom:3px}
.lesson{scroll-margin-top:88px;background:white;border:1px solid var(--line);border-radius:var(--radius);padding:clamp(24px,4vw,42px);margin-bottom:22px;box-shadow:0 12px 38px rgba(15,23,42,.055)}
.lesson-head{display:flex;gap:15px;align-items:flex-start;margin-bottom:24px}
.num{flex:0 0 48px;height:48px;border-radius:15px;display:grid;place-items:center;background:#eaf2ff;color:var(--blue);font-weight:900}
.lesson h2{margin:0;font-size:clamp(1.7rem,3vw,2.45rem);letter-spacing:-.035em;line-height:1.1}
.kicker{margin:4px 0 0;color:var(--muted)}
.callout{padding:17px 18px;border-radius:16px;background:#eff6ff;border:1px solid #dbeafe;margin:18px 0}
.callout strong{color:#1d4ed8}
.two-col{display:grid;grid-template-columns:1fr 1fr;gap:18px}
.info-card{border:1px solid var(--line);border-radius:18px;padding:19px;background:#fbfcfe}
.info-card h3{margin:0 0 8px;font-size:1.08rem}
.info-card p{margin:0;color:var(--muted)}
.code{background:#07111f;color:#dbeafe;border-radius:16px;padding:16px;overflow:auto;font-family:"Courier New",monospace;font-size:.82rem}
/* Peptide animation */
.peptide-lab{position:relative;min-height:240px;border-radius:20px;overflow:hidden;background:linear-gradient(145deg,#06111f,#10213a);color:white;margin:20px 0;padding:26px}
.peptide-title{font-weight:850;margin-bottom:28px}
.peptide-stage{position:relative;height:125px}
.aa-unit{position:absolute;top:28px;padding:14px 16px;border-radius:15px;background:rgba(255,255,255,.08);border:1px solid rgba(255,255,255,.13);font-family:"Courier New",monospace;font-weight:bold}
.aa-left{left:4%;animation:leftMeet 5s ease-in-out infinite}
.aa-right{right:4%;animation:rightMeet 5s ease-in-out infinite}
.water{position:absolute;left:50%;top:72px;transform:translateX(-50%);color:#7dd3fc;font-weight:900;opacity:0;animation:waterOut 5s ease-in-out infinite}
.bond-label{position:absolute;left:50%;top:8px;transform:translateX(-50%);color:#5eead4;font-size:.8rem;font-weight:850;opacity:0;animation:bondIn 5s ease-in-out infinite}
@keyframes leftMeet{0%,18%{transform:translateX(0)}45%,75%{transform:translateX(42px)}100%{transform:translateX(0)}}
@keyframes rightMeet{0%,18%{transform:translateX(0)}45%,75%{transform:translateX(-42px)}100%{transform:translateX(0)}}
@keyframes waterOut{0%,42%{opacity:0;transform:translate(-50%,0)}55%,75%{opacity:1;transform:translate(-50%,25px)}100%{opacity:0;transform:translate(-50%,35px)}}
@keyframes bondIn{0%,48%{opacity:0}58%,78%{opacity:1}100%{opacity:0}}
/* Explorer */
.explorer-wrap{margin-top:24px}
.legend{display:flex;gap:8px;flex-wrap:wrap;margin:15px 0}
.legend button,.filter-btn{border:0;cursor:pointer;border-radius:999px;padding:9px 12px;font-weight:800;font-size:.78rem;background:#eef2f7;color:#465268}
.filter-btn.active{outline:2px solid #1e293b;outline-offset:2px}
.dot{width:9px;height:9px;display:inline-block;border-radius:50%;margin-right:6px}
.explorer-grid{display:grid;grid-template-columns:minmax(300px,.9fr) minmax(0,1.4fr);gap:18px}
.aa-list{display:grid;grid-template-columns:repeat(4,1fr);gap:9px;align-content:start}
.aa-btn{position:relative;border:1px solid var(--line);background:white;border-radius:15px;padding:13px 8px;text-align:center;cursor:pointer;transition:.18s}
.aa-btn:hover,.aa-btn.active{transform:translateY(-2px);box-shadow:0 8px 20px rgba(15,23,42,.08);border-color:var(--cat)}
.aa-btn .one{font-size:1.28rem;font-weight:950;display:block;color:var(--cat)}
.aa-btn .three{font-size:.72rem;color:#718096;font-weight:800}
.detail{min-height:435px;border:1px solid var(--line);border-radius:22px;padding:24px;background:linear-gradient(145deg,#fff,#f9fbff);display:grid;grid-template-columns:minmax(230px,.85fr) 1.15fr;gap:26px;align-items:center}
.structure-box{background:#fff;border:1px solid #e6eaf1;border-radius:20px;padding:18px;min-height:265px;display:grid;place-items:center;box-shadow:inset 0 0 30px rgba(15,23,42,.025)}
.structure-box img{width:100%;max-height:240px;object-fit:contain;display:block}
.detail h3{font-size:2.15rem;letter-spacing:-.04em;margin:0 0 4px}
.codes{color:#748095;font-weight:850;margin-bottom:15px}
.badges{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:17px}
.badge{display:inline-flex;align-items:center;border-radius:999px;padding:7px 10px;font-size:.76rem;font-weight:850;background:#eef2f7}
.detail-copy{color:var(--muted);margin:0}
.fact{margin-top:18px;padding:14px 15px;border-left:4px solid var(--cat);background:#f8fafc;border-radius:0 13px 13px 0}
.search{width:100%;border:1px solid var(--line);border-radius:14px;padding:12px 14px;margin:10px 0 13px;outline:none}
.search:focus{border-color:#93c5fd;box-shadow:0 0 0 4px #dbeafe}
/* pI */
.formula{font-family:"Courier New",monospace;font-weight:bold;text-align:center;padding:18px;border-radius:16px;background:#eaf7ff;border:1px solid #bae6fd;color:#0369a1;font-size:1.08rem;margin:16px 0}
/* Quiz */
.quiz{background:linear-gradient(145deg,#07111f,#0e2039);color:white}
.quiz .num{background:rgba(94,234,212,.12);color:#5eead4}
.quiz .kicker{color:#a8b6ca}
.quiz-card{max-width:760px;margin:22px auto 0;background:rgba(255,255,255,.06);border:1px solid rgba(255,255,255,.10);border-radius:20px;padding:24px}
.q-counter{color:#94a3b8;font-size:.82rem;font-weight:800}
.q-text{font-size:1.3rem;font-weight:850;margin:8px 0 18px}
.options{display:grid;gap:10px}
.opt{text-align:left;border:1px solid rgba(255,255,255,.12);background:rgba(255,255,255,.06);color:white;border-radius:13px;padding:13px 14px;cursor:pointer}
.opt:hover{background:rgba(255,255,255,.11)}
.opt.correct{border-color:#34d399;background:rgba(52,211,153,.16)}
.opt.wrong{border-color:#fb7185;background:rgba(251,113,133,.14)}
.feedback{min-height:44px;color:#d3deec;margin:14px 0}
.quiz-actions{display:flex;justify-content:space-between;gap:12px;align-items:center}
.next{border:0;border-radius:12px;padding:11px 15px;background:#5eead4;color:#06211e;font-weight:900;cursor:pointer}
.score{font-weight:900}
footer{padding:30px 0 50px;color:#79869a;text-align:center;font-size:.88rem}
@media(max-width:850px){
  .module-nav{grid-template-columns:repeat(2,1fr)}
  .two-col,.explorer-grid,.detail{grid-template-columns:1fr}
  .aa-list{grid-template-columns:repeat(5,1fr)}
  .structure-box{min-height:220px}
}
@media(max-width:560px){
  .coursebar-inner{height:auto;min-height:64px;padding:8px 0}
  .brand span.brand-name{display:none}
  .course-intro{padding-top:38px}
  .module-nav{grid-template-columns:1fr 1fr}
  .aa-list{grid-template-columns:repeat(4,1fr)}
  .lesson{padding:22px 18px}
  .two-col{grid-template-columns:1fr}
  .peptide-lab{padding:20px 12px}
  .aa-unit{font-size:.72rem;padding:10px}
  .aa-left{left:0} .aa-right{right:0}
}
@media(prefers-reduced-motion:reduce){
 *{animation:none!important;transition:none!important;scroll-behavior:auto!important}
}