:root{font-family:Inter,ui-sans-serif,system-ui,sans-serif;color:var(--ink);background:var(--mist);font-size:16px}*{box-sizing:border-box}body{margin:0}button,select,textarea{font:inherit}button,a,select{ -webkit-tap-highlight-color:transparent}button{cursor:pointer}button:focus-visible,a:focus-visible,select:focus-visible,textarea:focus-visible{outline:3px solid var(--focus);outline-offset:4px}header{height:86px;border-bottom:1px solid var(--silver);background:var(--surface);display:flex;align-items:center;justify-content:space-between;padding:0 4%;gap:20px}.brand{color:inherit;text-decoration:none;display:flex;align-items:center;gap:12px;font-size:21px;font-weight:750}.logo{background:var(--ink);color:var(--mist);border-radius:10px;padding:7px 11px;font-family:Georgia,serif}.brand small{font-size:12px;border-left:1px solid var(--silver);padding-left:12px;color:var(--muted)}.header-note{font-size:14px;color:var(--muted)}.layout{display:grid;grid-template-columns:245px minmax(0,1fr);max-width:1480px;margin:auto}aside{padding:42px 24px;border-right:1px solid var(--silver);min-height:calc(100vh - 86px)}.eyebrow{font-size:12px;font-weight:750;letter-spacing:1.6px;color:var(--muted)}#subjects{display:grid;gap:10px;margin-top:22px}.subject-button{border:0;background:transparent;text-align:left;border-radius:10px;color:var(--ink);display:flex;align-items:center;gap:12px;padding:14px 10px;font-size:14px;font-weight:650}.subject-button.active{background:var(--ink);color:var(--ink)}.subject-icon{width:32px;height:32px;border-radius:8px;display:grid;place-items:center;background:var(--ice);color:var(--ink);font-size:18px}.active .subject-icon{background:var(--blue);color:var(--ink)}.aside-note{border-top:1px solid var(--silver);margin-top:54px;padding-top:25px;color:var(--muted);font-size:14px;line-height:1.6}.aside-note b{display:block;color:var(--ink);margin-top:12px}.mini-book{font-size:24px}main{padding:42px 48px;min-width:0}.intro{display:flex;align-items:center;justify-content:space-between;gap:20px;margin-bottom:34px}h1{font-size:clamp(30px,3vw,42px);letter-spacing:-1.6px;margin:12px 0}p{line-height:1.65}.intro p{color:var(--muted);margin:0}.edition{background:var(--ice);padding:13px 17px;border-radius:10px;color:var(--muted);font-size:12px;line-height:1.9}.edition b{font-weight:650;color:var(--ink)}.subject-heading{display:flex;justify-content:space-between;gap:24px;align-items:center}h2{font-size:28px;margin:8px 0 24px;letter-spacing:-.6px}label{color:var(--muted);font-size:14px}select{display:block;background:var(--surface);border:1px solid var(--field-border);border-radius:8px;padding:10px 36px 10px 12px;color:var(--ink);max-width:100%;margin-top:5px}.tabs{display:flex;gap:27px;border-bottom:1px solid var(--silver);margin-bottom:26px}.tabs button{border:0;background:none;padding:15px 0;color:var(--muted);font-size:14px;font-weight:650;border-bottom:3px solid transparent}.tabs button[aria-selected=true]{border-color:var(--ink);color:var(--ink)}.tabs span{background:var(--ice);padding:3px 7px;border-radius:5px;margin-left:5px;font-size:12px}.notes-grid{display:grid;grid-template-columns:minmax(0,1.6fr) minmax(220px,1fr);gap:22px}.panel{background:var(--surface);border:1px solid var(--silver);border-radius:14px;padding:28px}h3{font-size:22px;margin:0 0 20px;letter-spacing:-.4px}.note-point{padding:0 0 18px;margin-bottom:18px;border-bottom:1px solid var(--silver)}.note-point:last-child{border:0;margin:0;padding:0}.note-point b{display:block;margin-bottom:7px}.note-point p{color:var(--muted);margin:0}.tip{background:var(--ice);border-color:var(--blue)}.tip h3{font-size:18px}.tip p{color:var(--ink)}.tag{font-size:12px;font-weight:650;color:var(--muted);letter-spacing:1px}.tip .example{border-top:1px solid var(--blue);padding-top:18px}.card-top{display:flex;justify-content:space-between;color:var(--muted);font-size:14px;margin-bottom:18px}.flashcard{display:flex;flex-direction:column;align-items:center;justify-content:center;width:100%;min-height:300px;text-align:center;background:var(--ink);color:var(--ink);border:0;border-radius:16px;padding:35px}.flashcard .eyebrow{color:var(--ink)}.flashcard .card-text{font-size:clamp(23px,3vw,32px);line-height:1.5;max-width:670px;margin:25px 0}.flashcard small{color:var(--ink);font-size:14px}.controls{display:flex;justify-content:center;gap:12px;flex-wrap:wrap;margin-top:22px}.btn{border:1px solid var(--field-border);background:var(--surface);border-radius:8px;padding:11px 19px;color:var(--ink);font-weight:650;font-size:14px}.btn.primary{background:var(--ink);color:var(--ink);border-color:var(--ink)}.btn.lime{background:var(--mist);border-color:var(--mist);color:var(--ink)}.btn:disabled{opacity:.45;cursor:default}.question-meta{color:var(--muted);font-size:14px;margin-bottom:14px}.question{font-size:21px;line-height:1.6;font-weight:600}textarea{display:block;width:100%;min-height:130px;resize:vertical;border:1px solid var(--field-border);border-radius:10px;padding:15px;background:var(--surface);color:var(--ink);margin:12px 0 20px}.answer{margin-top:22px;background:var(--ice);border-radius:10px;padding:22px}.answer h4{margin:0 0 10px}.answer p{margin:0;color:var(--ink)}.session-end{text-align:center;padding:35px}.session-end .big{font-size:50px;font-weight:700;color:var(--ink)}footer{font-size:12px;color:var(--muted);margin-top:28px;line-height:1.6}@media(max-width:1000px){main{padding:32px 25px}.layout{grid-template-columns:205px 1fr}.notes-grid{grid-template-columns:1fr}.header-note{display:none}}@media(max-width:680px){header{height:70px}.layout{display:block}aside{padding:20px 18px 0;border:0;min-height:0}aside>.eyebrow,.aside-note{display:none}#subjects{display:flex;overflow:auto;margin:0;gap:8px}.subject-button{white-space:nowrap;padding:10px;font-size:13px}.subject-icon{width:25px;height:25px}main{padding:26px 18px}.edition{display:none}.intro{margin-bottom:25px}.subject-heading{align-items:start;flex-direction:column;gap:0}.subject-heading label{width:100%;margin-bottom:12px}select{width:100%}.tabs{gap:20px}.tabs button{font-size:13px}.panel{padding:22px}.flashcard{min-height:280px;padding:24px}}@media(prefers-reduced-motion:no-preference){button{transition:background .18s,color .18s}.panel{animation:appear .2s ease}@keyframes appear{from{opacity:.6;transform:translateY(4px)}to{opacity:1;transform:translateY(0)}}}