:root{
  --green:#2e7d32; --green-d:#1b5e20; --green-l:#e8f5e9;
  --exam-green:#5a9e1e; --exam-green-d:#4c8c17; --exam-black:#1d1f1c;
  --amber:#f3c026; --amber-l:#fbe6a2; --amber-d:#8a6d00;
  --ink:#1b2430; --muted:#5b6b7b; --line:#e2e8ee; --bg:#eef1ee; --card:#fff;
  --ok:#2e7d32; --ok-bg:#e6f4ea; --bad:#c62828; --bad-bg:#fdecea;
  --radius:12px; --shadow:0 2px 10px rgba(20,40,30,.07); --maxw:920px;
}
*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{font-family:"Segoe UI",system-ui,-apple-system,"Noto Sans",Arial,sans-serif;color:var(--ink);background:var(--bg);line-height:1.55;-webkit-text-size-adjust:100%}
img{max-width:100%}
a{color:#1565c0;text-decoration:none}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 16px}

/* ===== Global top bar (home) ===== */
.top{background:linear-gradient(135deg,var(--green),var(--green-d));color:#fff;position:sticky;top:0;z-index:50;box-shadow:0 2px 8px rgba(0,0,0,.15)}
.top .wrap{display:flex;align-items:center;gap:12px;height:60px}
.top .logo{font-size:26px}
.top h1{font-size:17px;margin:0;font-weight:700}
.top .sub{font-size:12px;opacity:.85}
.top .home-btn{margin-left:auto;background:rgba(255,255,255,.16);color:#fff;border:0;padding:8px 14px;border-radius:20px;font-size:14px;cursor:pointer}
.top .home-btn:hover{background:rgba(255,255,255,.28)}

/* ===== Home ===== */
.hero{padding:30px 0 10px;text-align:center}
.hero h2{font-size:24px;margin:.2em 0}
.hero p{color:var(--muted);max-width:640px;margin:8px auto}
.grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(260px,1fr));gap:16px;margin:20px 0 34px}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:20px;box-shadow:var(--shadow);display:flex;flex-direction:column}
.card h3{margin:0 0 6px;font-size:19px;color:var(--green-d)}
.card .jp{font-size:12px;color:var(--muted);margin-bottom:12px}
.card .meta{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:14px}
.pill{background:var(--green-l);color:var(--green-d);border-radius:20px;padding:4px 12px;font-size:13px;font-weight:600}
.pill.gray{background:#eef2f6;color:var(--muted)}
.card .best{font-size:13px;color:var(--muted);margin-bottom:12px;min-height:18px}
.btn{display:inline-block;text-align:center;background:var(--green);color:#fff;border:0;border-radius:10px;padding:12px 18px;font-size:15px;font-weight:600;cursor:pointer;transition:background .15s}
.btn:hover{background:var(--green-d)}
.btn.block{width:100%}
.btn.ghost{background:#fff;color:var(--green-d);border:1.5px solid var(--green)}
.btn.ghost:hover{background:var(--green-l)}
.card .actions{margin-top:auto;display:flex;gap:10px}
.section-title{font-size:15px;font-weight:700;color:var(--muted);text-transform:uppercase;letter-spacing:.5px;margin:26px 0 6px}
.books{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:12px;margin-bottom:40px}
.book{display:flex;align-items:center;gap:12px;background:var(--card);border:1px solid var(--line);border-radius:12px;padding:14px;box-shadow:var(--shadow)}
.book .ic{font-size:26px}
.book b{display:block;font-size:15px}
.book span{font-size:12px;color:var(--muted)}
.foot{text-align:center;color:var(--muted);font-size:13px;padding:26px 0 40px}

/* ===== EXAM interface (giống thi thật) ===== */
.exam{max-width:1120px;margin:0 auto;background:#fff;min-height:100vh;box-shadow:0 0 24px rgba(0,0,0,.06)}
.exam-top{background:var(--exam-black);color:#fff;display:flex;align-items:center;gap:16px;padding:8px 18px;position:sticky;top:0;z-index:40}
.et-left{font-size:14px;line-height:1.35}
.et-left b{font-size:16px}
.et-mid{margin:0 auto;display:flex;align-items:center;gap:10px}
.et-mid .clk{font-size:20px}
.et-lbl{font-size:12px;opacity:.85}
.et-time{font-size:20px;font-weight:700;font-variant-numeric:tabular-nums;letter-spacing:1px}
.et-time.low{color:#ff6b6b}
.et-end{background:var(--amber);color:#5a4500;border:0;border-radius:6px;padding:9px 16px;font-size:14px;font-weight:700;cursor:pointer;white-space:nowrap}
.et-end:hover{background:#e6ad00}
.et-end:disabled{opacity:.6;cursor:default}
.exam-sub{background:var(--exam-green);color:#fff;display:flex;justify-content:space-between;padding:6px 18px;font-size:13px;font-weight:600}
.exam-sub .ex-home{color:#fff;text-decoration:none;margin-right:4px}
body.in-exam .top{display:none}

.exam-body{display:flex;align-items:flex-start}
.exam-nav{width:120px;flex:none;border-right:1px solid var(--line);padding:10px 6px;position:sticky;top:96px;max-height:calc(100vh - 96px);overflow-y:auto;background:#fafbfa}
.nav-group{margin-bottom:14px}
.nav-glabel{font-size:12px;font-weight:700;color:var(--exam-green-d);padding:2px 6px;border-left:3px solid var(--exam-green);margin-bottom:6px;line-height:1.2}
.nav-glabel small{display:block;font-weight:400;color:var(--muted);font-size:10px}
.nav-tabs{display:flex;flex-wrap:wrap;gap:5px}
.navtab{width:30px;height:28px;border:0;border-radius:5px;background:#37413a;color:#fff;font-size:12px;font-weight:700;cursor:pointer;position:relative}
.navtab:hover{background:#4b5a4f}
.navtab.done{background:var(--exam-green)}
.navtab.cur{outline:3px solid var(--amber);outline-offset:1px;z-index:1}
.navtab.correct{background:var(--ok)}
.navtab.wrong{background:var(--bad)}

.exam-main{flex:1;min-width:0;padding:26px 30px}
.qtext{font-size:18px;font-weight:600;margin-bottom:18px;color:#222;line-height:1.5}
.qimg{text-align:center;margin:0 0 18px}
.qimg img{border:1px solid var(--line);border-radius:8px;max-height:360px}
.audiobar{margin:0 0 20px}
.audiobar audio{width:100%;filter:grayscale(.2)}

.optlist{display:flex;flex-direction:column;gap:12px;max-width:760px}
.optbox{border:1px solid #cfd6da;border-radius:8px;padding:15px 18px;font-size:16px;cursor:pointer;background:#fff;transition:.1s;display:flex;align-items:center;gap:12px}
.optbox:hover{border-color:var(--amber);background:#fffbe9}
.optbox.lettered .ll{display:inline-flex;width:26px;height:26px;border-radius:50%;border:1.5px solid var(--muted);align-items:center;justify-content:center;font-weight:700;font-size:14px;color:var(--muted)}
.optbox.sel{background:var(--amber);border-color:#d9ab00;font-weight:600}
.optbox.sel .ll{background:#fff;border-color:#d9ab00;color:#7a5c00}
.optbox.rc{background:var(--ok-bg);border-color:var(--ok);border-width:2px}
.optbox.rw{background:var(--bad-bg);border-color:var(--bad);border-width:2px}
.optbox.rc .ll{background:var(--ok);border-color:var(--ok);color:#fff}
.optbox.rw .ll{background:var(--bad);border-color:var(--bad);color:#fff}

.imgrow{display:grid;grid-template-columns:repeat(auto-fit,minmax(140px,1fr));gap:14px;max-width:820px}
.imgcell{border:2px solid #cfd6da;border-radius:8px;padding:8px;cursor:pointer;background:#fff;text-align:center;transition:.1s}
.imgcell:hover{border-color:var(--amber)}
.imgcell img{height:140px;object-fit:contain;width:100%}
.imgcell.sel{border-color:#d9ab00;background:var(--amber-l)}
.imgcell.rc{border-color:var(--ok);background:var(--ok-bg)}
.imgcell.rw{border-color:var(--bad);background:var(--bad-bg)}

.fillwrap{max-width:420px}
.fillwrap input{width:100%;padding:14px 16px;border:1px solid #cfd6da;border-radius:8px;font-size:17px}
.fillwrap input:focus{border-color:var(--amber);outline:none}
.fillwrap .hint{font-size:12px;color:var(--muted);margin-top:6px}
.fres{margin-top:10px;font-size:15px;font-weight:600}
.fres.ok{color:var(--ok)}
.fres.bad{color:var(--bad)}
.script{margin-top:16px;padding:12px 15px;border-radius:8px;background:#f0f4f8;font-size:15px;max-width:760px}
.script b{color:var(--green-d)}
.expl{margin-top:12px;padding:12px 15px;border-radius:8px;background:#fff8e1;border:1px solid #ffe08a;font-size:15px;max-width:760px;line-height:1.55}
.expl b{color:#8a6d00}

.exam-foot{display:flex;align-items:center;gap:16px;margin-top:30px;padding-top:18px;border-top:1px solid var(--line);max-width:820px}
.navbtn{background:#fff;border:1.5px solid var(--exam-green);color:var(--exam-green-d);border-radius:8px;padding:11px 20px;font-size:15px;font-weight:600;cursor:pointer}
.navbtn:hover:not(:disabled){background:var(--green-l)}
.navbtn:disabled{opacity:.4;cursor:default}
.pos{margin:0 auto;font-size:14px;color:var(--muted);font-variant-numeric:tabular-nums}

/* ===== Result modal ===== */
.overlay{position:fixed;inset:0;background:rgba(15,25,20,.55);display:none;align-items:center;justify-content:center;z-index:100;padding:16px}
.overlay.show{display:flex}
.result{background:#fff;border-radius:18px;max-width:460px;width:100%;padding:26px;text-align:center;box-shadow:0 10px 40px rgba(0,0,0,.3)}
.result .score-ring{width:130px;height:130px;border-radius:50%;margin:6px auto 14px;display:flex;align-items:center;justify-content:center;flex-direction:column;color:#fff}
.result .score-ring b{font-size:34px;line-height:1}
.result .score-ring span{font-size:13px;opacity:.9}
.result h2{margin:.1em 0}
.result .verdict{font-size:15px;font-weight:700;padding:6px 16px;border-radius:20px;display:inline-block;margin:6px 0 14px}
.result .verdict.pass{background:var(--ok-bg);color:var(--ok)}
.result .verdict.fail{background:var(--bad-bg);color:var(--bad)}
.result .breakdown{display:flex;gap:12px;margin:10px 0 18px}
.result .breakdown div{flex:1;background:var(--bg);border-radius:12px;padding:12px}
.result .breakdown b{display:block;font-size:22px;color:var(--green-d)}
.result .breakdown span{font-size:12px;color:var(--muted)}
.result .rbtns{display:flex;gap:10px}

@media(max-width:680px){
  .exam-nav{width:74px}
  .navtab{width:26px;height:26px;font-size:11px}
  .exam-main{padding:18px 14px}
  .qtext{font-size:16px}
  .et-mid .et-lbl{display:none}
  .exam-sub{font-size:11px}
}

/* ====== KHÓA HỌC (freemium) ====== */
.card{position:relative}
.tag-free{position:absolute;top:10px;right:10px;background:var(--ok);color:#fff;font-size:11px;font-weight:800;letter-spacing:.5px;padding:3px 9px;border-radius:20px}
.tag-lock{position:absolute;top:10px;right:10px;background:#fff3d6;color:var(--amber-d);border:1px solid var(--amber-l);font-size:11px;font-weight:800;padding:3px 9px;border-radius:20px}
.card.is-locked{opacity:.92}
.card.is-locked h3{color:var(--muted)}
.btn.locked{background:linear-gradient(135deg,var(--amber),#e0a800);color:#4a3a00}
.course-banner{display:flex;align-items:center;gap:14px;flex-wrap:wrap;justify-content:space-between;
  background:linear-gradient(135deg,#fff8e6,#ffeec2);border:1px solid var(--amber-l);
  border-radius:var(--radius);padding:14px 18px;margin:6px 0 18px;box-shadow:var(--shadow)}
.course-banner .cb-l{flex:1;min-width:230px;color:#5a4a10}
.course-banner .btn{white-space:nowrap}
.course-cta{text-align:center;padding:6px 2px}
.course-cta .cc-emoji{font-size:44px;line-height:1}
.course-cta h2{margin:6px 0}
.course-cta .cc-price{font-size:30px;font-weight:900;color:var(--green-d);margin:12px 0}
.course-cta .cc-price span{display:block;font-size:13px;font-weight:600;color:var(--muted)}
.upsell{margin-top:16px;padding:14px;border-radius:12px;background:linear-gradient(135deg,#fff8e6,#ffeec2);border:1px solid var(--amber-l);text-align:center}
.upsell .up-title{font-weight:800;color:#5a4a10;margin-bottom:4px}
.upsell p{margin:4px 0 10px;font-size:14px;color:#6a5820}
.course-banner.member{background:linear-gradient(135deg,#e8f5e9,#d3ead6);border-color:#bfe0c4}
.course-banner.member .cb-l{color:var(--green-d)}
.cc-qr{margin:12px auto;max-width:320px;display:flex;gap:12px;align-items:center;background:#f7faf5;border:1px solid var(--line);border-radius:12px;padding:10px}
.cc-qr img{width:120px;height:120px;object-fit:contain;background:#fff;border:1px solid var(--line);border-radius:8px;padding:4px}
.cc-qr-cap{font-size:12px;color:var(--muted);text-align:left;line-height:1.5}