:root{
  --ink:#14213d;--ink2:#1d315f;--blue:#315efb;--cyan:#28c9e8;--paper:#f4f6fb;--white:#fff;
  --line:#dfe5f0;--muted:#65738f;--green:#138a63;--green-bg:#eafaf4;--red:#b63d48;--red-bg:#fff0f1;
  --amber:#a56508;--amber-bg:#fff7e8;--radius:24px;--shadow:0 16px 40px rgba(20,33,61,.08);
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--paper);color:var(--ink);font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;line-height:1.55}
button,input,select{font:inherit}
button{min-height:46px}
button:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid rgba(49,94,251,.28);outline-offset:2px}
.topbar{position:sticky;top:0;z-index:30;display:flex;align-items:center;justify-content:space-between;gap:16px;padding:12px max(16px,calc((100vw - 1220px)/2));background:rgba(255,255,255,.96);backdrop-filter:blur(16px);border-bottom:1px solid var(--line)}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none;color:var(--ink)}
.brand-mark{display:grid;place-items:center;width:42px;height:42px;border-radius:14px;background:var(--ink);color:#fff;font-weight:900}
.brand strong{display:block;letter-spacing:.08em;font-size:.85rem}
.brand small{display:block;color:var(--muted);font-weight:700}
.top-actions{display:flex;align-items:center;gap:10px}
.status-pill{padding:8px 12px;border-radius:999px;font-size:.78rem;font-weight:800;background:#eef2f8;color:var(--muted)}
.status-pill.online{background:var(--green-bg);color:var(--green)}
.status-pill.offline{background:var(--amber-bg);color:var(--amber)}
.app-shell{max-width:1220px;margin:0 auto;padding:34px 20px 72px}
.hero{display:grid;grid-template-columns:minmax(0,1.5fr) minmax(300px,.7fr);gap:30px;align-items:end;padding:48px;border-radius:32px;background:linear-gradient(135deg,var(--ink),#183b7a);color:#fff;box-shadow:var(--shadow)}
.eyebrow{margin:0 0 8px;color:var(--cyan);font-size:.75rem;font-weight:900;letter-spacing:.14em}
.hero h1{font-size:clamp(2.35rem,5vw,4.8rem);line-height:.98;margin:.16em 0 .3em;letter-spacing:-.04em}
.hero h1 span{color:#9eeaf4}
.hero-copy{max-width:720px;color:#dbe4f6;font-size:1.08rem;margin:0}
.hero-metrics{display:grid;grid-template-columns:repeat(3,1fr);gap:10px}
.hero-metrics div{padding:20px 14px;border:1px solid rgba(255,255,255,.17);background:rgba(255,255,255,.08);border-radius:18px}
.hero-metrics strong{display:block;font-size:1.3rem}
.hero-metrics span{display:block;font-size:.78rem;color:#cbd6ec}
.card{background:var(--white);border:1px solid var(--line);border-radius:var(--radius);box-shadow:0 10px 28px rgba(20,33,61,.04)}
.session-panel{margin-top:24px;padding:28px;display:grid;grid-template-columns:1fr 1.4fr;gap:28px}
.session-panel h2,.teacher-head h2{margin:.1em 0 .35em;font-size:1.7rem}
.muted{color:var(--muted)}
.session-form{display:grid;grid-template-columns:1fr 1.4fr auto;gap:12px;align-items:end}
label{font-weight:800;font-size:.88rem}
label small{display:block;color:var(--muted);font-weight:500;margin-top:4px}
input,select{width:100%;margin-top:6px;padding:13px 14px;border:1px solid var(--line);border-radius:12px;background:#fff;color:var(--ink)}
button{border:0;border-radius:12px;padding:11px 17px;background:var(--blue);color:#fff;font-weight:850;cursor:pointer}
button:hover{filter:brightness(.98)}
button:disabled{opacity:.55;cursor:not-allowed}
.secondary-button,.ghost-button{background:#eef2ff;color:var(--blue)}
.ghost-button{min-height:40px;padding:8px 12px}
.text-button{background:transparent;color:var(--blue);padding:2px 0;min-height:auto}
.saved-sessions{grid-column:2;display:flex;gap:10px;align-items:end}
.saved-sessions label{flex:1}
.workspace{display:grid;grid-template-columns:330px minmax(0,1fr);gap:24px;margin-top:24px;align-items:start}
.sidebar{position:sticky;top:82px;padding:20px}
.group-card{padding-bottom:18px;border-bottom:1px solid var(--line)}
.group-row{display:flex;align-items:center;justify-content:space-between;gap:12px}
.group-row strong{font-size:1.15rem}
.learner-chips{display:flex;flex-wrap:wrap;gap:7px;margin-top:12px}
.learner-chip{padding:7px 10px;border-radius:999px;background:#f0f3f8;color:var(--muted);font-size:.78rem;font-weight:800}
.learner-chip.active{background:var(--ink);color:#fff}
.overall-progress{padding:18px 0}
.progress-head{display:flex;justify-content:space-between;font-size:.82rem;font-weight:800}
.progress-track,.mini-progress{height:9px;background:#edf0f5;border-radius:99px;overflow:hidden;margin-top:8px}
.progress-track span,.mini-progress span{display:block;height:100%;background:linear-gradient(90deg,var(--blue),var(--cyan));border-radius:inherit}
.module-nav{display:grid;gap:8px}
.module-link{display:grid;grid-template-columns:34px 1fr auto;gap:10px;align-items:center;width:100%;text-align:left;background:#fff;color:var(--ink);border:1px solid transparent;padding:10px;border-radius:14px}
.module-link:hover{background:#f7f9fd}
.module-link.active{background:#eef2ff;border-color:#d8e0ff;color:#18388f}
.module-link.done .module-letter{background:var(--green-bg);color:var(--green)}
.module-letter{display:grid;place-items:center;width:32px;height:32px;background:#eef2f8;border-radius:10px;font-size:.78rem}
.module-link strong{display:block;font-size:.83rem}
.module-link small{display:block;color:var(--muted);font-size:.72rem;font-weight:650}
.module-percent{font-size:.72rem;color:var(--muted)}
.offline-note{margin-top:18px;padding:14px;border-radius:14px;background:#f7f9fd}
.offline-note strong,.offline-note span{display:block}
.offline-note span{margin-top:3px;color:var(--muted);font-size:.78rem}
.activity{padding:34px}
.module-intro{padding-bottom:24px;border-bottom:1px solid var(--line)}
.module-intro h2{font-size:2rem;line-height:1.1;margin:.1em 0 .2em}
.module-intro p:not(.eyebrow){margin:0;color:var(--muted)}
.question-area{padding-top:26px}
.question-topline{display:flex;justify-content:space-between;gap:12px;align-items:center}
.question-counter{font-weight:800;color:var(--muted);font-size:.85rem}
.skill-tag{padding:7px 10px;border-radius:999px;background:#eef2ff;color:var(--blue);font-size:.76rem;font-weight:850}
.turn-banner{display:grid;grid-template-columns:auto 1fr auto;gap:12px;align-items:center;margin:20px 0;padding:12px 14px;background:#f7f9fd;border-radius:14px}
.turn-banner span,.turn-banner small{color:var(--muted);font-size:.78rem}
.turn-banner strong{font-size:1rem}
.question-prompt{font-size:clamp(1.65rem,3vw,2.45rem);line-height:1.15;letter-spacing:-.025em;margin:24px 0 6px}
.question-support{color:var(--muted);margin:0 0 22px}
.answer-form{display:grid;gap:10px}
.choice{display:flex;align-items:center;gap:12px;padding:14px;border:1px solid var(--line);border-radius:14px;cursor:pointer;background:#fff;font-size:1rem}
.choice:hover{border-color:#bac7e5;background:#fafbff}
.choice input{width:20px;height:20px;margin:0;accent-color:var(--blue)}
.choice span{font-weight:650}
.input-answer{display:grid;gap:4px;max-width:560px}
.input-answer input{font-size:1.15rem;padding:15px}
.question-actions{display:flex;justify-content:space-between;gap:12px;margin-top:20px;padding-top:20px;border-top:1px solid var(--line)}
.hint-panel,.feedback-panel{margin-top:16px;padding:16px;border-radius:14px}
.hint-panel{background:var(--amber-bg);color:#744807;border:1px solid #f4deb8}
.feedback-panel.correct{background:var(--green-bg);color:#0d684a;border:1px solid #bde8d8}
.feedback-panel.incorrect{background:var(--red-bg);color:#8d2f38;border:1px solid #f1c8cc}
.feedback-panel strong{font-size:1.05rem}
.feedback-panel p{margin:.35em 0}
.misconception{margin-top:10px;padding-top:10px;border-top:1px solid currentColor;font-size:.86rem;opacity:.9}
.retry-note{font-weight:800}
.next-row{display:flex;justify-content:flex-end;margin-top:16px}
.module-complete{text-align:center;padding:46px 20px}
.celebration{display:grid;place-items:center;width:72px;height:72px;margin:0 auto 18px;border-radius:24px;background:var(--green-bg);color:var(--green);font-size:2rem;font-weight:900}
.module-complete h2{font-size:2rem;margin:.1em 0}
.module-complete p:not(.eyebrow){max-width:650px;margin:0 auto 20px;color:var(--muted)}
.teacher-panel{margin-top:24px;padding:28px}
.teacher-head{display:flex;justify-content:space-between;gap:24px;align-items:start}
.teacher-actions{display:flex;gap:8px;flex-wrap:wrap}
.metric-grid{display:grid;grid-template-columns:repeat(5,1fr);gap:12px;margin:22px 0}
.metric{padding:18px;border:1px solid var(--line);border-radius:16px;background:#fbfcff}
.metric span{display:block;color:var(--muted);font-size:.76rem;font-weight:750}
.metric strong{display:block;font-size:1.8rem;margin-top:4px}
.table-wrap{overflow:auto;border:1px solid var(--line);border-radius:16px}
table{width:100%;border-collapse:collapse;min-width:860px}
th,td{text-align:left;padding:13px 14px;border-bottom:1px solid var(--line);font-size:.84rem}
th{background:#f7f9fd;color:var(--muted);font-size:.72rem;text-transform:uppercase;letter-spacing:.05em}
.teacher-notes{margin-top:18px;color:var(--muted)}
.teacher-notes summary{cursor:pointer;font-weight:800;color:var(--ink)}
footer{display:flex;justify-content:space-between;gap:16px;color:var(--muted);font-size:.78rem;padding:26px 4px}
.hidden{display:none!important}

@media(max-width:980px){
  .hero{grid-template-columns:1fr;padding:34px}
  .session-panel{grid-template-columns:1fr}
  .session-form{grid-template-columns:1fr 1fr}
  .session-form button{grid-column:1/-1}
  .saved-sessions{grid-column:1}
  .workspace{grid-template-columns:280px minmax(0,1fr)}
  .metric-grid{grid-template-columns:repeat(3,1fr)}
}
@media(max-width:760px){
  .topbar{align-items:flex-start}
  .top-actions{flex-direction:column;align-items:flex-end;gap:6px}
  .status-pill{font-size:.68rem}
  .app-shell{padding:18px 12px 60px}
  .hero{padding:26px 20px;border-radius:24px}
  .hero-metrics{grid-template-columns:1fr 1fr 1fr}
  .hero-metrics div{padding:14px 10px}
  .session-panel{padding:20px}
  .session-form{grid-template-columns:1fr}
  .saved-sessions{display:grid}
  .workspace{grid-template-columns:1fr}
  .sidebar{position:relative;top:auto}
  .module-nav{grid-template-columns:1fr 1fr}
  .module-link{grid-template-columns:30px 1fr}
  .module-percent{display:none}
  .activity{padding:22px 18px}
  .turn-banner{grid-template-columns:1fr auto}
  .turn-banner small{grid-column:1/-1}
  .question-actions{position:sticky;bottom:0;background:#fff;padding:12px 0 calc(12px + env(safe-area-inset-bottom));z-index:10}
  .teacher-head{display:block}
  .teacher-actions{margin-top:14px}
  .metric-grid{grid-template-columns:1fr 1fr}
  footer{display:grid}
}
@media(max-width:460px){
  .brand small{display:none}
  .ghost-button{font-size:.76rem}
  .hero h1{font-size:2.35rem}
  .hero-metrics{grid-template-columns:1fr}
  .module-nav{grid-template-columns:1fr}
  .question-topline{align-items:flex-start}
  .question-actions{display:grid;grid-template-columns:1fr 1fr}
  .metric-grid{grid-template-columns:1fr}
}
@media(prefers-reduced-motion:reduce){
  *{scroll-behavior:auto!important;transition:none!important;animation:none!important}
}


.practice-lab{margin-top:34px;padding-top:28px;border-top:1px solid var(--line)}
.practice-head{display:flex;justify-content:space-between;gap:24px;align-items:end}
.practice-head h2{font-size:1.6rem;margin:.1em 0 .25em}
.practice-controls{display:flex;gap:10px;align-items:end;min-width:min(100%,420px)}
.practice-controls label{flex:1}
.practice-card{margin-top:18px;padding:22px;border:1px solid var(--line);border-radius:18px;background:#fbfcff}
.practice-card h3{font-size:1.45rem;line-height:1.3;margin:20px 0}
.practice-card .answer-form{grid-template-columns:minmax(0,1fr) auto;align-items:end}
.practice-card>.text-button{margin-top:14px}
.research-alignment p{margin:.55em 0}
@media(max-width:760px){
  .practice-head{display:block}
  .practice-controls{display:grid;grid-template-columns:1fr;margin-top:16px;min-width:0}
  .practice-card .answer-form{grid-template-columns:1fr}
}