/* OpenEdu — open practice web. Vanilla CSS, no framework. Friendly + clean. */
/* Be Vietnam Pro tự host (đầy đủ tiếng Việt, không phụ thuộc Google Fonts) */
@font-face{font-family:'Be Vietnam Pro';font-weight:400;font-style:normal;font-display:swap;src:url('fonts/BeVietnamPro-Regular.ttf') format('truetype')}
@font-face{font-family:'Be Vietnam Pro';font-weight:500;font-style:normal;font-display:swap;src:url('fonts/BeVietnamPro-Medium.ttf') format('truetype')}
@font-face{font-family:'Be Vietnam Pro';font-weight:600;font-style:normal;font-display:swap;src:url('fonts/BeVietnamPro-SemiBold.ttf') format('truetype')}
@font-face{font-family:'Be Vietnam Pro';font-weight:700;font-style:normal;font-display:swap;src:url('fonts/BeVietnamPro-Bold.ttf') format('truetype')}
@font-face{font-family:'Be Vietnam Pro';font-weight:800;font-style:normal;font-display:swap;src:url('fonts/BeVietnamPro-ExtraBold.ttf') format('truetype')}
:root{
  --green:#2f8f3c; --green-bright:#46b152; --green-ink:#236e2e; --forest:#103527;
  --amber:#f3a712; --amber-soft:#fff3da;
  --blue:#3a7bd5; --blue-soft:#eaf2fc;
  --ink:#26302b; --muted:#5f6f67; --dim:#8a978f;
  --bg:#f6faf5; --card:#ffffff; --rule:#e4ebe2; --soft:#eef5ec;
  --ok:#2f8f3c; --bad:#d9534f;
  --r:16px; --r-sm:10px;
  --shadow:0 10px 28px rgba(16,53,39,.07);
  --display:'Be Vietnam Pro',system-ui,sans-serif; --body:'Be Vietnam Pro',system-ui,sans-serif;
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;color:var(--ink);font-family:var(--body);line-height:1.55;
  display:flex;flex-direction:column;min-height:100vh;-webkit-font-smoothing:antialiased;
  background:
    radial-gradient(820px 460px at 8% -6%, rgba(70,177,82,.13), transparent 60%),
    radial-gradient(760px 440px at 102% -4%, rgba(243,167,18,.10), transparent 58%),
    radial-gradient(680px 520px at 50% 118%, rgba(58,123,213,.07), transparent 60%),
    var(--bg);
  background-attachment:fixed}
a{color:inherit;text-decoration:none}
img{max-width:100%;display:block}

/* ---- top bar ---- */
.topbar{position:sticky;top:0;z-index:30;padding:12px 0;background:rgba(255,255,255,.9);
  backdrop-filter:blur(10px);border-bottom:1px solid var(--rule)}
.topbar-in{max-width:1060px;margin:0 auto;padding:0 20px;display:flex;align-items:center;
  justify-content:space-between;gap:14px}
.brand{display:flex;align-items:center;gap:9px}
.brand-mark{display:grid;place-items:center;width:34px;height:34px;border-radius:10px;
  background:linear-gradient(150deg,var(--green-bright),var(--green));color:#fff;
  font-family:var(--display);font-weight:800;font-size:20px;line-height:1}
.brand-name{font-family:var(--display);font-weight:800;font-size:20px;color:var(--forest)}
.topright{display:flex;align-items:center;gap:10px}
.topnav{display:flex;gap:6px}
.topnav a{font-weight:600;font-size:14.5px;color:var(--muted);padding:7px 12px;border-radius:999px}
.topnav a:hover{color:var(--forest);background:var(--soft)}
.topnav a.active{color:var(--green-ink);background:var(--soft)}

.app{flex:1;width:100%;max-width:1060px;margin:0 auto;padding:26px 20px 50px}

/* ---- hero ---- */
.hero{background:linear-gradient(160deg,#0e3a27,#0a2a1c);color:#fff;border-radius:22px;
  padding:34px 30px;margin-bottom:26px;position:relative;overflow:hidden}
.hero h1{font-family:var(--display);font-weight:800;font-size:clamp(26px,4.5vw,38px);margin:0 0 8px;line-height:1.1}
.hero p{margin:0;max-width:62ch;color:#cfe0d4;font-size:16.5px}
.hero .pills{display:flex;flex-wrap:wrap;gap:8px;margin-top:16px}
.hero .pill{font-size:12.5px;font-weight:600;color:#dff4e2;background:rgba(255,255,255,.10);
  border:1px solid rgba(255,255,255,.16);padding:5px 12px;border-radius:999px}

/* ---- section heading ---- */
.sec-title{font-family:var(--display);font-weight:700;font-size:22px;color:var(--forest);margin:28px 0 14px}
.sec-sub{color:var(--muted);font-size:14px;margin:-8px 0 16px}
.search-wrap{position:relative;display:flex;align-items:center;margin:2px 0 14px}
.search-wrap .search-ic{position:absolute;left:15px;font-size:15px;opacity:.55;pointer-events:none}
.search-wrap input{width:100%;font-family:var(--body);font-size:15.5px;padding:13px 44px;border:1.5px solid var(--rule);
  border-radius:14px;background:rgba(255,255,255,.85);color:var(--ink);outline:none;transition:border-color .15s,box-shadow .15s}
.search-wrap input:focus{border-color:var(--green-bright);box-shadow:0 0 0 4px rgba(70,177,82,.13)}
.search-wrap input::placeholder{color:var(--dim)}
.search-wrap input::-webkit-search-cancel-button{-webkit-appearance:none}
.search-clear{position:absolute;right:9px;width:30px;height:30px;border:0;border-radius:9px;background:var(--soft);
  color:var(--muted);cursor:pointer;font-size:13px;display:grid;place-items:center}
.search-clear:hover{background:#e1e9df;color:var(--ink)}
.grade-chips{display:flex;flex-wrap:wrap;gap:8px;margin:4px 0 18px}
.chip-row{display:flex;flex-wrap:wrap;gap:8px;margin:0 0 10px}
.chip-row:last-of-type{margin-bottom:18px}
.gchip.dim{opacity:.42;font-weight:500}
.gchip.dim:hover{opacity:.7}
.soon{background:var(--soft);border:1px dashed var(--rule);border-radius:14px;padding:18px 20px;
  color:var(--muted);font-size:14.5px;margin-bottom:10px}
.gchip{font-family:var(--display);font-weight:600;font-size:14px;padding:7px 16px;border-radius:999px;
  border:1.5px solid var(--rule);background:var(--card);color:var(--muted);cursor:pointer;transition:border-color .15s,background .15s,color .15s}
.gchip:hover{border-color:var(--green-bright);color:var(--forest)}
.gchip.active{background:var(--green);color:#fff;border-color:var(--green)}

/* ---- skill grid ---- */
.skill-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(min(100%,250px),1fr));gap:14px}
.skill-card{display:flex;flex-direction:column;gap:10px;background:var(--card);border:1px solid var(--rule);
  border-radius:var(--r);padding:18px;cursor:pointer;transition:transform .14s,box-shadow .2s,border-color .2s;text-align:left}
.skill-card:hover{transform:translateY(-3px);box-shadow:var(--shadow);border-color:rgba(70,177,82,.5)}
.skill-card .sc-top{display:flex;align-items:center;gap:11px}
.skill-card .sc-icon{font-size:24px;width:42px;height:42px;display:grid;place-items:center;border-radius:12px;background:var(--soft)}
.skill-card .sc-name{font-family:var(--display);font-weight:700;font-size:16.5px;color:var(--forest);line-height:1.2}
.skill-card .sc-strand{font-size:12px;color:var(--dim)}
.mbar{height:8px;background:var(--soft);border-radius:999px;overflow:hidden}
.mbar > i{display:block;height:100%;background:linear-gradient(90deg,var(--green-bright),var(--green));border-radius:999px}
.sc-meta{display:flex;justify-content:space-between;font-size:12px;color:var(--muted)}

.feature-card{grid-column:1/-1;display:flex;align-items:center;justify-content:space-between;gap:18px;
  background:linear-gradient(150deg,var(--amber-soft),#fff);border:1px solid #f0e2c4;border-radius:var(--r);padding:20px 22px}
.feature-card .fc-txt h3{font-family:var(--display);margin:0 0 4px;color:#8a5a06;font-size:18px}
.feature-card .fc-txt p{margin:0;color:#9a7330;font-size:14px}

/* ---- buttons ---- */
.btn{display:inline-flex;align-items:center;gap:8px;font-family:var(--display);font-weight:700;font-size:15px;
  padding:11px 20px;border-radius:12px;border:0;cursor:pointer;background:var(--green);color:#fff;transition:background .15s,transform .1s}
.btn:hover{background:var(--green-ink)}
.btn:active{transform:translateY(1px)}
.btn.amber{background:var(--amber);color:#3a2a04}.btn.amber:hover{background:#dd9405}
.btn.ghost{background:var(--card);color:var(--forest);border:1.5px solid var(--rule)}
.btn.ghost:hover{border-color:var(--green-bright);background:var(--soft)}
.btn[disabled]{opacity:.45;cursor:not-allowed}

/* ---- run / question ---- */
.run-top{display:flex;align-items:center;gap:14px;margin-bottom:18px}
.run-top .rt-badge{font-family:var(--display);font-weight:700;color:var(--forest);background:var(--soft);padding:6px 14px;border-radius:999px;font-size:14px}
.run-top .rt-prog{flex:1;height:10px;background:var(--soft);border-radius:999px;overflow:hidden}
.run-top .rt-prog > i{display:block;height:100%;background:linear-gradient(90deg,var(--green-bright),var(--green));transition:width .25s}
.run-top .rt-count{font-weight:600;color:var(--muted);font-size:14px;font-variant-numeric:tabular-nums}

.qcard{background:var(--card);border:1px solid var(--rule);border-radius:20px;padding:26px 26px 22px;box-shadow:var(--shadow)}
.q-meta{display:flex;flex-wrap:wrap;gap:7px;margin-bottom:12px}
.qm{font-family:var(--display);font-weight:600;font-size:11.5px;padding:4px 11px;border-radius:999px;background:var(--soft);color:var(--green-ink)}
.qm.d-easy{background:#eafaec;color:#236e2e}
.qm.d-mid{background:#fff3da;color:#9a6a06}
.qm.d-hard{background:#fdeceb;color:#b5332e}
.q-stem{font-size:21px;font-weight:600;color:var(--ink);line-height:1.45;margin:0 0 6px}
.q-asset{display:flex;justify-content:center;margin:16px 0}
.q-asset svg{max-width:100%}
.objects{display:flex;flex-wrap:wrap;gap:14px;justify-content:center;align-items:center}
.obj-group{display:flex;flex-wrap:wrap;gap:6px;max-width:230px;justify-content:center;font-size:30px;line-height:1}
.obj-plus{font-family:var(--display);font-weight:800;font-size:30px;color:var(--muted)}

.options{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;margin-top:18px}
.opt{display:flex;align-items:center;gap:12px;text-align:left;background:var(--card);border:1.5px solid var(--rule);
  border-radius:14px;padding:14px 16px;cursor:pointer;font-size:16px;font-weight:600;color:var(--ink);transition:border-color .15s,background .15s}
.opt:hover{border-color:var(--green-bright);background:var(--soft)}
.opt .opt-key{font-family:var(--display);font-weight:700;width:28px;height:28px;border-radius:8px;display:grid;place-items:center;
  background:var(--soft);color:var(--green-ink);flex:none}
.opt.correct{border-color:var(--ok);background:#eafaec}
.opt.correct .opt-key{background:var(--ok);color:#fff}
.opt.wrong{border-color:var(--bad);background:#fdeceb}
.opt.wrong .opt-key{background:var(--bad);color:#fff}
.opt[disabled]{cursor:default}

.explain{margin-top:16px;border-radius:14px;padding:14px 16px;font-size:15px;line-height:1.6}
.explain.ok{background:#eafaec;border:1px solid #bfe6c6}
.explain.bad{background:#fdeceb;border:1px solid #f3c9c7}
.explain .ex-head{font-family:var(--display);font-weight:700;margin-bottom:3px}
.explain.ok .ex-head{color:var(--green-ink)} .explain.bad .ex-head{color:#a23631}
.run-actions{display:flex;justify-content:flex-end;margin-top:18px}

/* exam 3-column layout (fill the empty sides) */
.exam-grid{display:grid;grid-template-columns:200px minmax(0,1fr) 220px;gap:20px;align-items:start}
.exam-side{background:var(--card);border:1px solid var(--rule);border-radius:var(--r);padding:18px 16px}
.exam-left{text-align:center}
.exam-mascot{font-size:46px;line-height:1}
.el-title{font-family:var(--display);font-weight:700;color:var(--forest);margin-top:6px;font-size:16px}
.el-score{margin-top:12px;font-size:14.5px;color:var(--muted)}
.el-score b{font-family:var(--display);font-size:24px;color:var(--green-ink)}
.el-bar{margin-top:8px}
.el-meta{margin-top:14px;font-size:12.5px;color:var(--dim);line-height:1.5}
.nav-title{font-family:var(--display);font-weight:700;font-size:12.5px;letter-spacing:.01em;color:var(--dim)}
.nav-dots{display:flex;flex-wrap:wrap;gap:8px;margin-top:11px}
.ndot{width:30px;height:30px;border-radius:9px;display:grid;place-items:center;font-family:var(--display);font-weight:700;font-size:13px;background:var(--soft);color:var(--muted)}
.ndot.cur{box-shadow:inset 0 0 0 2px var(--green);color:var(--green-ink)}
.ndot.ok{background:var(--green);color:#fff}
.ndot.bad{background:var(--bad);color:#fff}
.tip{margin-top:16px;background:var(--amber-soft);border:1px solid #f0e2c4;border-radius:10px;padding:11px 13px;font-size:13px;color:#8a5a06;line-height:1.5}
@media (max-width:1040px){ .exam-grid{grid-template-columns:1fr} .exam-side{display:none} }

/* ---- summary ---- */
.summary{text-align:center;background:var(--card);border:1px solid var(--rule);border-radius:20px;padding:36px 24px;box-shadow:var(--shadow)}
.summary .big{font-family:var(--display);font-weight:800;font-size:52px;color:var(--green);line-height:1}
.summary h2{font-family:var(--display);margin:6px 0 4px;color:var(--forest)}
.summary p{color:var(--muted);margin:0 0 18px}
.summary .sum-actions{display:flex;gap:10px;justify-content:center;flex-wrap:wrap}
.sum-stars{font-size:34px;margin-bottom:4px}
.sum-ring{width:120px;height:120px;border-radius:50%;margin:6px auto 2px;display:grid;place-items:center}
.sum-ring-in{width:92px;height:92px;border-radius:50%;background:var(--card);display:grid;place-items:center}
.sum-ring-in b{font-family:var(--display);font-weight:800;font-size:27px;color:var(--green-ink);line-height:1}
.sum-ring-in small{font-size:12px;color:var(--muted)}
.sum-skills{max-width:430px;margin:14px auto 4px;display:flex;flex-direction:column;gap:8px}
.sum-skill{display:flex;justify-content:space-between;align-items:center;background:var(--soft);border-radius:10px;padding:9px 14px;font-size:14.5px;color:var(--forest)}
.ss-score{font-family:var(--display);font-weight:700}
.ss-score.ok{color:var(--green-ink)} .ss-score.low{color:var(--bad)}
.sum-suggest{max-width:520px;margin:18px auto 2px;border-top:1px solid var(--rule);padding-top:16px}
.sum-suggest .ss-head{font-family:var(--display);font-weight:700;color:var(--forest);font-size:15px;margin-bottom:11px}
.ss-chips{display:flex;flex-wrap:wrap;gap:8px;justify-content:center}
.ss-chip{display:inline-flex;align-items:center;gap:7px;background:var(--soft);border:1px solid var(--rule);
  border-radius:999px;padding:8px 14px;font-size:14px;font-weight:600;color:var(--forest);transition:border-color .15s,background .15s}
.ss-chip:hover{border-color:var(--green-bright);background:var(--card)}
/* suggest for you */
.suggest-box{background:linear-gradient(150deg,#eafaec,#fff);border:1px solid #cfe6cf;border-radius:var(--r);padding:18px 20px;margin-bottom:18px}
.sg-head{font-size:13.5px;color:var(--muted);margin-bottom:12px}
.sg-head b{font-family:var(--display);font-size:17px;color:var(--forest)}
.sg-cards{display:flex;flex-wrap:wrap;gap:10px;margin-bottom:14px}
.sg-card{display:flex;align-items:center;gap:10px;background:var(--card);border:1px solid var(--rule);border-radius:12px;padding:9px 14px;cursor:pointer;text-align:left}
.sg-card:hover{border-color:var(--green-bright)}
.sg-ic{font-size:20px}
.sg-tx{display:flex;flex-direction:column;line-height:1.25}
.sg-tx b{font-family:var(--display);font-size:14px;color:var(--forest)}
.sg-tx small{font-size:11.5px;color:var(--dim)}
/* TikZ-built SVG figure in a question */
.q-svg{max-width:min(100%,440px);height:auto;margin:0 auto}
.newbanner{background:var(--amber-soft);border:1px solid #f0e2c4;border-radius:12px;padding:11px 16px;margin-bottom:16px;font-size:14.5px;color:#8a5a06;display:flex;align-items:center;gap:12px;flex-wrap:wrap}
.newbanner button{font-family:var(--display);font-weight:700;background:var(--amber);color:#3a2a04;border:0;border-radius:8px;padding:6px 14px;cursor:pointer}
.more-wrap{display:flex;justify-content:center;margin-top:8px}
.about-foot{margin-top:22px;padding-top:16px;border-top:1px solid var(--rule);display:flex;align-items:center;justify-content:space-between;gap:12px;font-size:13.5px;color:var(--muted);flex-wrap:wrap}
.about-foot b{color:var(--forest);font-family:var(--display)}
.toast{position:fixed;left:50%;bottom:24px;transform:translate(-50%,18px);background:var(--forest);color:#fff;
  padding:11px 20px;border-radius:999px;font-family:var(--display);font-weight:600;font-size:14px;
  box-shadow:0 8px 24px rgba(16,53,39,.28);opacity:0;transition:opacity .3s,transform .3s;z-index:200}
.toast.show{opacity:1;transform:translate(-50%,0)}
.loading{text-align:center;color:var(--muted);padding:60px 20px;font-size:15px}
.btn.danger{background:var(--bad);color:#fff}.btn.danger:hover{background:#c0403c}
/* confirm modal */
.modal-ov{position:fixed;inset:0;background:rgba(16,32,24,.45);display:grid;place-items:center;z-index:300;opacity:0;transition:opacity .2s;padding:20px}
.modal-ov.show{opacity:1}
.modal{background:var(--card);border-radius:18px;padding:24px;max-width:380px;width:100%;text-align:center;box-shadow:0 20px 50px rgba(16,53,39,.25);transform:translateY(12px) scale(.98);transition:transform .2s}
.modal-ov.show .modal{transform:none}
.modal-ic{font-size:34px;margin-bottom:4px}
.modal h3{font-family:var(--display);color:var(--forest);margin:0 0 8px;font-size:20px}
.modal p{color:var(--muted);margin:0 0 20px;font-size:14.5px;line-height:1.6}
.modal-actions{display:flex;gap:10px;justify-content:center}
/* header stat pill (lấp khoảng trống giữa header) */
.topstat{display:flex;justify-content:center;flex:1}
.ts-pill{font-family:var(--display);font-weight:700;font-size:13px;color:var(--green-ink);background:var(--soft);padding:7px 15px;border-radius:999px}
.ts-pill.ts-muted{color:var(--muted)}
/* analysis row sub */
.an-sub{grid-column:1/-1;font-size:12px;color:var(--dim);margin-top:2px}

/* ---- analysis ---- */
.stat-row{display:grid;grid-template-columns:repeat(auto-fit,minmax(140px,1fr));gap:12px;margin-bottom:22px}
.stat{background:var(--card);border:1px solid var(--rule);border-radius:var(--r);padding:16px 18px}
.stat .s-num{font-family:var(--display);font-weight:800;font-size:28px;color:var(--green-ink)}
.stat .s-lab{font-size:13px;color:var(--muted)}
.an-list{display:flex;flex-direction:column;gap:10px}
.an-item{display:grid;grid-template-columns:1fr auto;gap:6px 14px;align-items:center;background:var(--card);
  border:1px solid var(--rule);border-radius:var(--r-sm);padding:13px 16px}
.an-item .an-name{font-weight:600;color:var(--forest)}
.an-item .an-bar{grid-column:1/-1}
.an-item .an-pct{font-variant-numeric:tabular-nums;font-weight:700;color:var(--muted)}

/* ---- prose (about) ---- */
.prose{background:var(--card);border:1px solid var(--rule);border-radius:var(--r);padding:28px 34px;max-width:920px}
.prose p{text-align:justify;text-justify:inter-word}
.prose h2{font-family:var(--display);color:var(--forest);margin:20px 0 8px}
.prose h2:first-child{margin-top:0}
.prose p,.prose li{color:var(--ink);font-size:15.5px;line-height:1.7}
.prose code{background:var(--soft);border:1px solid var(--rule);border-radius:6px;padding:1px 6px;font-size:.9em}

/* ---- footer ---- */
.sitefoot{border-top:1px solid var(--rule);background:var(--card);margin-top:32px}
.foot-grid{max-width:1060px;margin:0 auto;padding:28px 20px 8px;display:grid;
  grid-template-columns:1.6fr 1fr 1fr;gap:28px}
.foot-brand .foot-logo{font-weight:800;font-size:18px;color:var(--green-ink);display:flex;align-items:center;gap:7px}
.foot-brand .brand-mark{font-size:20px}
.foot-brand p{margin:8px 0 0;font-size:13.5px;color:var(--muted);line-height:1.65;max-width:34ch}
.foot-brand a{color:var(--green-ink);font-weight:600}
.foot-col h4{margin:2px 0 10px;font-size:14px;font-weight:700;letter-spacing:0;color:var(--ink)}
.foot-col a{display:block;font-size:14px;color:var(--ink);padding:4px 0;font-weight:500;text-decoration:none}
.foot-col a:hover{color:var(--green-ink)}
.foot-bottom{max-width:1060px;margin:0 auto;padding:14px 20px 22px;font-size:12.5px;color:var(--dim);
  border-top:1px solid var(--rule)}
.foot-bottom a{color:var(--green-ink);font-weight:600}
/* small note */
.prose .muted-note{color:var(--muted);font-size:13px;margin-top:4px}
.more-rest{color:var(--dim);font-weight:500;font-size:.85em}
.empty{text-align:center;color:var(--muted);padding:40px 20px}

/* ---- comparison table (About) ---- */
.cmp{width:100%;border-collapse:separate;border-spacing:0;margin:14px 0 6px;font-size:14.5px}
.cmp th,.cmp td{padding:11px 14px;text-align:left;vertical-align:top;border-bottom:1px solid var(--rule)}
.cmp thead th{background:var(--ink);color:#fff;font-weight:700;font-size:13.5px}
.cmp thead th:first-child{border-top-left-radius:10px}
.cmp thead th:last-child{border-top-right-radius:10px}
.cmp td:first-child{font-weight:700;color:var(--ink);white-space:nowrap}
.cmp .col-them{color:var(--muted)}
.cmp .col-oe{background:var(--soft);color:var(--ink)}
.cmp .col-oe b{color:var(--green-ink)}
.cmp tbody tr:last-child td{border-bottom:0}
.cmp tbody tr:last-child .col-oe{border-bottom-right-radius:10px}
@media (max-width:680px){
  .cmp{font-size:14px}
  .cmp,.cmp tbody,.cmp tr,.cmp td{display:block;width:100%}
  .cmp thead{display:none}
  .cmp tbody tr{border:1px solid var(--rule);border-radius:12px;margin-bottom:12px;overflow:hidden;background:var(--card)}
  .cmp td{border:0;padding:10px 14px;white-space:normal}
  .cmp td:first-child{background:var(--soft);color:var(--green-ink);font-weight:700;font-size:13px;
    border-bottom:1px solid var(--rule)}
  .cmp .col-them,.cmp .col-oe{display:flex;gap:8px;background:transparent}
  .cmp .col-oe{border-top:1px dashed var(--rule)}
  .cmp .col-them::before{content:"Nơi khác";flex:0 0 70px;color:var(--dim);font-weight:600;font-size:12px;padding-top:1px}
  .cmp .col-oe::before{content:"OpenEdu";flex:0 0 70px;color:var(--green-ink);font-weight:700;font-size:12px;padding-top:1px}
}

@media (max-width:680px){
  .app{padding:18px 14px 40px}
  .hero{padding:26px 20px}
  .options{grid-template-columns:1fr}
  .foot-grid{grid-template-columns:1fr;gap:18px;padding:22px 16px 4px}
  .foot-brand p{max-width:none}
  .topbar{padding:10px 0}
  .topbar-in{padding:0 14px}
  .topstat{display:none}
  .brand-mark{width:28px;height:28px;font-size:17px}
  .brand-name{font-size:17px}
  .topnav{gap:2px}
  .topnav a{padding:6px 7px;font-size:12px;white-space:nowrap}
  .topright{gap:6px}
  .theme-btn{width:32px;height:32px;font-size:14px}
  .prose{padding:22px 18px}
  .q-stem{font-size:19px}
}
@media (max-width:430px){
  .brand-name{display:none}
  .topnav a{padding:6px 6px;font-size:11.5px}
  .topnav{gap:0}
}


/* ====================== DARK MODE ====================== */
html[data-theme="dark"]{
  --green-ink:#7fd594; --forest:#d4ecdb;
  --ink:#e7efe9; --muted:#a6b6ac; --dim:#7e9085;
  --bg:#0f1714; --card:#16201b; --rule:#27332c; --soft:#1c2821;
  --shadow:0 12px 30px rgba(0,0,0,.42);
}
html[data-theme="dark"] body{background:
  radial-gradient(820px 460px at 8% -6%, rgba(70,177,82,.18), transparent 60%),
  radial-gradient(760px 440px at 102% -4%, rgba(243,167,18,.10), transparent 58%),
  radial-gradient(680px 520px at 50% 118%, rgba(58,123,213,.12), transparent 60%),
  var(--bg);}
html[data-theme="dark"] .topbar{background:rgba(15,23,20,.86)}
html[data-theme="dark"] .search-wrap input{background:rgba(255,255,255,.05)}
html[data-theme="dark"] .search-clear:hover{background:#26332c}
html[data-theme="dark"] .cmp thead th,
html[data-theme="dark"] .cmp td:first-child{background:#26332c;color:#eef5ec}
html[data-theme="dark"] .cmp .col-oe{background:rgba(70,177,82,.10)}
html[data-theme="dark"] .opt.correct{background:rgba(70,177,82,.18)}
html[data-theme="dark"] .opt.wrong{background:rgba(217,83,79,.18)}
html[data-theme="dark"] .explain.ok{background:rgba(70,177,82,.13);border-color:rgba(70,177,82,.40)}
html[data-theme="dark"] .explain.bad{background:rgba(217,83,79,.13);border-color:rgba(217,83,79,.40)}
html[data-theme="dark"] .feature-card{background:linear-gradient(150deg,#2a2415,#181f1a);border-color:#3b3320}
html[data-theme="dark"] .feature-card .fc-txt h3{color:#f3c87a}
html[data-theme="dark"] .feature-card .fc-txt p{color:#cdb27e}
html[data-theme="dark"] .suggest-box{background:linear-gradient(150deg,rgba(70,177,82,.14),#16201b);border-color:#2c4030}
/* figures keep a white panel so LaTeX/SVG lines stay readable on dark */
html[data-theme="dark"] .q-asset{background:#fff;border-radius:14px;padding:12px 10px}
/* theme toggle button */
.theme-btn{width:36px;height:36px;border-radius:999px;border:1.5px solid var(--rule);background:var(--card);
  cursor:pointer;font-size:16px;line-height:1;display:grid;place-items:center;color:var(--ink);flex:none}
.theme-btn:hover{border-color:var(--green-bright)}