/* Workspace edition: desktop study rail; mobile dashboard and thumb navigation. */
:root{--rail:222px;--topbar:80px;--radius:16px}body{background:var(--paper)}header{height:var(--topbar);max-width:none;position:sticky;top:0;z-index:20;background:var(--paper);padding:16px 30px;border-bottom:1px solid var(--line)}header .brand{width:calc(var(--rail) - 30px);flex-shrink:0}header nav{margin-left:auto}header .header-controls{margin-left:5px}header .brand-icon{border-radius:10px}.desktop-rail{position:fixed;left:0;top:var(--topbar);bottom:0;width:var(--rail);border-right:1px solid var(--line);padding:32px 18px;overflow-y:auto;z-index:15;background:var(--paper);display:flex;flex-direction:column;gap:6px}.rail-label,.rail-bottom{font-size:9px;letter-spacing:1.5px;color:var(--muted);padding:0 14px;margin-bottom:13px}.desktop-rail>a{display:flex;align-items:center;gap:13px;padding:12px 14px;border-radius:9px;color:var(--muted);font-size:12px}.desktop-rail>a>span{font-size:19px;width:20px;text-align:center}.desktop-rail>a:hover,.desktop-rail>a[aria-current]{background:var(--surface-soft);color:var(--teal)}.desktop-rail>a[aria-current]{box-shadow:inset 3px 0 var(--teal);font-weight:650}.rail-divider{height:1px;background:var(--line);margin:15px 12px}.rail-ai{margin:20px 4px;padding:18px 15px;border:1px solid var(--line);border-radius:12px;background:linear-gradient(145deg,var(--surface-soft),var(--white))}.rail-ai .eyebrow{font-size:8px}.rail-ai p{font:20px/1.35 var(--serif);margin:12px 0}.rail-ai a{font-size:11px;color:var(--teal);font-weight:650}.rail-bottom{margin-top:auto;padding-top:25px;line-height:2}.rail-bottom strong{font-size:12px;font-weight:500;color:var(--teal)}body>main,.article main,.directory main,.quiz main,.result main{margin-left:var(--rail);margin-right:0;width:calc(100% - var(--rail));max-width:none;padding:40px clamp(28px,4vw,72px) 60px}body>footer{margin-left:var(--rail);max-width:none;padding:25px 35px}.mobile-dock{display:none}.workspace-greeting{display:flex;justify-content:space-between;align-items:center;padding:0 0 28px}.workspace-greeting .eyebrow{font-size:9px;margin:0 0 7px;display:block}.workspace-greeting h2{font:26px var(--serif)}.mini-pill{font-size:11px;color:var(--teal);padding:9px 15px;border:1px solid var(--line);border-radius:30px;background:var(--white)}.hero{background:linear-gradient(120deg,var(--surface-soft),var(--white));border:1px solid var(--line);border-radius:22px;padding:40px;min-height:470px;gap:25px;overflow:hidden}.hero h1{font-size:clamp(45px,4.7vw,72px)}.hero .eyebrow{font-size:8px;letter-spacing:1.2px}.hero-copy>p{font-size:13px;max-width:350px}.hero .actions{gap:17px;margin:25px 0}.hero .text-link{font-size:11px}.hero-foot{font-size:7px;gap:13px}.math-art{padding:10px 0}.art-label,.art-index{font-size:6px}.equation-tag{bottom:45px}.study-strip{display:grid;grid-template-columns:repeat(3,1fr);border:1px solid var(--line);border-radius:13px;margin:20px 0 42px;background:var(--white)}.study-strip a{display:flex;align-items:center;gap:14px;padding:20px}.study-strip a+a{border-left:1px solid var(--line)}.study-strip strong{color:var(--teal);font:23px var(--serif)}.study-strip span{font-size:12px;font-weight:600;line-height:1.6}.study-strip small{display:block;font-weight:400;color:var(--muted);font-size:10px}.study-strip b{margin-left:auto;font-size:18px;font-weight:400;color:var(--muted)}.study-strip a:hover{background:var(--surface-soft)}.section-heading h2{font-size:27px}.feature{border-radius:var(--radius);padding:25px}.feature h3{font-size:22px}.feature p{font-size:12px}.feature-grid{gap:15px}.geometry{margin:45px 0}.article main{max-width:1080px;padding-left:60px;padding-right:60px}.article h1{font-size:42px}.article main>p{font-size:15px}.article .toc{position:relative}.directory h1{max-width:760px}.directory main>a{border-radius:13px;padding:25px}.directory .practice-choices{display:grid;grid-template-columns:1fr 1fr;gap:24px}.page-intro{max-width:660px;color:var(--muted);font-size:15px}.practice-choice{display:block!important;padding:30px!important;background:var(--white);border:1px solid var(--line);border-radius:18px!important;transition:transform .2s}.practice-choice:hover{transform:translateY(-4px)}.practice-choice.advanced{background:linear-gradient(145deg,var(--surface-soft),var(--white))}.choice-tag{font-size:9px!important;letter-spacing:1px;color:var(--teal);padding:0!important;font-family:inherit!important}.choice-icon{display:block;font:40px var(--serif)!important;color:var(--teal);padding:27px 0!important}.practice-choice h2{font-size:28px;margin:0 0 15px}.practice-choice p{font-size:14px;color:var(--muted)}.choice-facts{display:flex;gap:20px;font-size:11px;color:var(--muted);margin:20px 0}.practice-choice strong{display:flex;justify-content:space-between;padding-top:20px;border-top:1px solid var(--line);font-size:13px;color:var(--teal)}.practice-guide{margin-top:45px}.practice-guide>div{display:grid;grid-template-columns:repeat(3,1fr);gap:25px;margin-top:20px}.practice-guide p{font-size:13px;color:var(--muted)}.practice-guide b{display:block;color:var(--ink);margin-bottom:8px}.practice-guide .note{color:var(--ink)}
/* Quiz layout and stateful answer controls. */
.practice-heading{display:flex;justify-content:space-between;align-items:center;gap:25px;margin-bottom:30px}.practice-heading .eyebrow{margin-bottom:12px}.practice-heading h1{font-size:38px;letter-spacing:-1px;margin:0}.quiet-link{font-size:12px;color:var(--muted)}.quiz-layout{display:grid;grid-template-columns:minmax(0,1fr) 245px;gap:28px;align-items:start}.quiz-main{min-width:0}.attempt-progress{display:flex;justify-content:space-between;gap:15px;color:var(--muted);font-size:11px}.attempt-progress b{font-size:18px;color:var(--ink)}.quiz-main progress{height:4px;width:100%;margin:15px 0 24px;border:0}.exam-card{background:var(--white);border:1px solid var(--line);border-radius:18px;padding:30px;box-shadow:var(--shadow)}.question-label{font-size:9px;letter-spacing:1.6px;color:var(--teal)}.exam-card h2{font:26px/1.55 var(--serif);letter-spacing:0;margin:16px 0 25px;overflow-wrap:anywhere}.answer-options{margin:0;padding:0;border:0;display:flex;flex-direction:column;gap:12px}.answer-option{display:flex;align-items:center;gap:15px;padding:15px;border:1px solid var(--line);border-radius:10px;background:var(--paper);cursor:pointer;position:relative;font-size:15px;line-height:1.5}.answer-option input{position:absolute;opacity:0;width:1px;height:1px}.answer-option:focus-within{outline:2px solid var(--teal);outline-offset:3px}.answer-option:hover{border-color:var(--teal)}.answer-option.selected{border-color:var(--teal);background:var(--surface-soft)}.option-badge{flex-shrink:0;display:grid;place-items:center;width:30px;height:30px;border:1px solid var(--line);border-radius:7px;font-size:12px;color:var(--muted)}.selected .option-badge{background:var(--accent-fill);color:var(--accent-ink);border-color:var(--accent-fill)}.selection-dot{margin-left:auto;width:16px;height:16px;border-radius:50%;border:1px solid var(--line);flex-shrink:0}.selected .selection-dot{border:4px solid var(--teal);background:var(--paper)}.answer-tools{display:flex;justify-content:space-between;align-items:center;gap:15px;margin-top:22px;font-size:10px;color:var(--muted)}.clear-answer{border:0;background:none;color:var(--teal);font-size:11px;cursor:pointer;white-space:nowrap;padding:8px}.question-controls{display:flex;align-items:center;justify-content:space-between;gap:10px;padding:22px 0 0}.primary-button,.secondary-button{display:inline-flex;align-items:center;justify-content:center;gap:4px;border:1px solid var(--line);padding:12px 19px;border-radius:9px;font-size:12px;font-weight:600;cursor:pointer;min-height:44px;text-decoration:none}.primary-button{background:var(--accent-fill);color:var(--accent-ink);border-color:var(--accent-fill)}.secondary-button{background:var(--white);color:var(--ink)}button:disabled{opacity:.4;cursor:default}.primary-button:hover:not(:disabled){filter:brightness(1.07);transform:translateY(-1px)}.position-count{font-size:11px;color:var(--muted)}.quiet-note{font-size:11px;color:var(--muted);margin:16px 0;line-height:1.7}.question-map{background:var(--white);padding:22px;border:1px solid var(--line);border-radius:16px;position:sticky;top:105px}.map-heading{display:flex;justify-content:space-between;align-items:center;margin-bottom:22px}.map-heading h2{font:20px var(--serif);letter-spacing:0}.map-heading>span{font-size:11px;color:var(--muted)}.question-grid{display:grid;grid-template-columns:repeat(5,1fr);gap:7px}.map-button{aspect-ratio:1;border:1px solid var(--line);border-radius:7px;background:var(--paper);color:var(--muted);font-size:11px;cursor:pointer}.map-button.answered{background:var(--surface-soft);color:var(--teal);border-color:var(--teal)}.map-button.current{outline:2px solid var(--teal);outline-offset:2px;font-weight:700}.map-legend{display:flex;justify-content:space-between;gap:8px;margin:20px 0;font-size:8px;color:var(--muted)}.map-legend i{display:inline-block;width:8px;height:8px;border:1px solid var(--muted);border-radius:2px;margin-right:4px}.map-legend .filled{background:var(--teal);border-color:var(--teal)}.marking-note{border-top:1px solid var(--line);padding-top:18px;margin-bottom:20px}.marking-note>b{font-size:8px;letter-spacing:1px;color:var(--muted)}.marking-note p{font-size:11px;display:flex;justify-content:space-between;margin:9px 0}.submit-attempt{width:100%}.question-map .quiet-note{text-align:center;margin-bottom:0}.submit-dialog{background:var(--white);color:var(--ink);border:1px solid var(--line);border-radius:18px;max-width:480px;width:calc(100% - 32px);padding:30px;box-shadow:0 30px 100px #0008}.submit-dialog::backdrop{background:#050a10bd;backdrop-filter:blur(5px)}.submit-dialog h2{font-size:32px;margin-bottom:20px}.submit-dialog p{font-size:14px;color:var(--muted)}.dialog-actions{display:flex;gap:12px;margin-top:25px}.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip-path:inset(50%);white-space:nowrap}.result-hero{display:grid;grid-template-columns:1fr auto;gap:35px;align-items:center;padding:35px;background:linear-gradient(125deg,var(--surface-soft),var(--white));border:1px solid var(--line);border-radius:20px}.result-kicker{font-size:8px;letter-spacing:1.4px;color:var(--teal)}.result-hero h1{font-size:43px;letter-spacing:-1.5px;margin:18px 0}.result-hero p{font-size:13px;max-width:450px;color:var(--muted)}.result-actions{display:flex;gap:12px;margin-top:25px}.score-orb{display:flex;flex-direction:column;align-items:center;justify-content:center;width:220px;height:220px;border:1px solid var(--teal);border-radius:50%;box-shadow:0 0 0 10px var(--paper),0 0 0 11px var(--line);gap:12px;color:var(--teal)}.score-orb>span{font-size:9px}.score-orb strong{font:52px var(--serif)}.score-orb small{font:16px 'Segoe UI',sans-serif;color:var(--muted)}.result-stats{display:grid;grid-template-columns:repeat(3,1fr);gap:15px;margin:22px 0 40px}.result-stats>div{padding:20px;border:1px solid var(--line);border-radius:12px;background:var(--white);display:flex;align-items:center;gap:13px}.result-stats strong{font-size:24px;font-weight:500}.result-stats>div>span:last-child{color:var(--muted);font-size:11px}.stat-dot{width:8px;height:8px;border-radius:50%;background:var(--muted)}.correct-dot{background:var(--teal)}.wrong-dot{background:#df8e83}.review-item{border:1px solid var(--line);border-radius:12px;margin:12px 0;background:var(--white);overflow:hidden}.review-item summary{cursor:pointer;display:flex;gap:18px;align-items:center;padding:22px;font-size:14px;line-height:1.6}.review-number{font-size:11px;color:var(--muted)}.verdict{font-size:10px;padding:4px 9px;border-radius:20px;background:var(--paper);color:var(--muted);margin-left:auto;white-space:nowrap}.verdict.positive{color:var(--teal);background:var(--surface-soft)}.verdict.negative{color:#d4776c}.review-content{border-top:1px solid var(--line);padding:25px}.answer-comparison{display:grid;grid-template-columns:1fr 1fr;gap:20px}.answer-comparison p{font-size:14px;line-height:1.7}.answer-comparison small{display:block;color:var(--muted);font-size:9px;letter-spacing:1px;margin-bottom:6px}.review-content h3{font-size:12px;color:var(--teal);margin:10px 0}.review-content>p{font-size:14px;line-height:1.9;margin:0;overflow-wrap:anywhere}
@media(min-width:1500px){body>main{padding-left:70px;padding-right:70px}.hero{min-height:500px}.quiz-layout{grid-template-columns:minmax(0,1fr) 280px}.exam-card{padding:40px}.question-grid{gap:10px}}
@media(min-width:761px) and (max-width:1100px){:root{--rail:185px}header{flex-wrap:nowrap;padding:14px 20px}header .brand{width:auto}header nav{order:0;width:auto;justify-content:end;margin-left:auto;padding:0}header nav>a:not(.ask-ai){display:none}.header-controls{margin-left:0}.desktop-rail{padding:25px 12px}.desktop-rail>a{font-size:11px;padding:10px;gap:8px}body>main,.article main,.directory main{padding:30px 25px 50px}.hero{padding:27px;grid-template-columns:1.2fr 1fr;min-height:420px}.hero h1{font-size:44px}.hero .actions{flex-wrap:wrap;gap:12px}.hero-foot{display:none}.feature-grid{grid-template-columns:1fr}.feature{display:grid;grid-template-columns:60px 1fr;column-gap:20px}.feature .tile-icon{grid-row:1/4;margin-bottom:0}.feature p{max-width:none}.study-strip a{padding:15px;gap:10px}.study-strip small{font-size:9px}.study-strip b{display:none}.study-strip strong{font-size:18px}.study-strip span{font-size:10px}.quiz-layout{grid-template-columns:minmax(0,1fr)}.question-map{position:static}.question-grid{grid-template-columns:repeat(10,1fr)}.question-map .marking-note{display:none}.map-legend{justify-content:start;gap:20px}.result-hero{grid-template-columns:1fr auto;padding:28px}.score-orb{width:150px;height:150px}.score-orb strong{font-size:38px}.score-orb>span{font-size:7px}.result-hero h1{font-size:35px}.article main{max-width:none}}
@media(max-width:760px){:root{--rail:0px;--topbar:68px}body{padding-bottom:84px}.desktop-rail{display:none}header{height:auto;min-height:68px;padding:14px 18px;flex-wrap:wrap;gap:10px}header .brand{width:auto}header nav{margin:0}header .header-controls{margin-left:auto}body>main,.article main,.directory main,.practice-workspace main{margin:0;width:100%;padding:25px 18px 35px;max-width:none}body>footer{margin:0;padding:25px 20px}header nav.open{display:flex}.mobile-dock{display:grid!important;grid-template-columns:repeat(5,1fr);gap:0;position:fixed;bottom:0;left:0;right:0;background:var(--white);border-top:1px solid var(--line);z-index:30;padding:7px 8px calc(7px + env(safe-area-inset-bottom));width:100%;box-shadow:0 -6px 30px #0002}.mobile-dock a{display:flex;flex-direction:column;gap:1px;align-items:center;font-size:9px;font-weight:500;color:var(--muted);border-radius:8px;padding:4px 0;min-height:49px}.mobile-dock a>span{font-size:21px;line-height:1.4}.mobile-dock a[aria-current]{background:var(--surface-soft);color:var(--teal);text-decoration:none}.mobile-dock a:last-child{color:var(--teal)}.workspace-greeting{padding:0 0 20px}.workspace-greeting .eyebrow{font-size:7px;letter-spacing:1.2px}.workspace-greeting h2{font-size:25px}.mini-pill{font-size:9px;padding:6px 10px}.hero{position:relative;display:block;min-height:0;padding:28px 25px;border-radius:18px}.hero h1{font-size:48px;line-height:1.03;max-width:80%}.hero-copy{position:relative;z-index:1}.hero-copy>p{max-width:90%;font-size:12px;line-height:1.8}.hero .eyebrow{font-size:7px;letter-spacing:1px;max-width:90%}.hero .actions{margin-bottom:0;flex-wrap:wrap;gap:15px}.hero .button{font-size:11px;padding:12px 16px;gap:15px}.hero .text-link{font-size:10px}.hero-foot{display:none}.hero .math-art{position:absolute;width:190px;height:190px;right:-65px;top:40px;opacity:.18;pointer-events:none;margin:0}.hero .art-label,.hero .art-index,.hero .equation-tag{display:none}.study-strip{display:flex;flex-direction:column;border-radius:12px;margin:15px 0 30px}.study-strip a{padding:14px 17px;gap:17px}.study-strip a+a{border-left:0;border-top:1px solid var(--line)}.study-strip span{font-size:12px}.study-strip small{display:inline;margin-left:10px;font-size:10px}.study-strip strong{font-size:18px}.study-strip b{font-size:18px}.section-heading{gap:12px;margin:23px 0 18px}.section-heading h2{font-size:25px}.feature-grid{display:flex;flex-direction:column;gap:12px}.feature{display:grid;grid-template-columns:48px 1fr;column-gap:15px;padding:21px 18px;border-radius:13px}.feature .tile-icon{grid-row:1/4;width:44px;height:44px;font-size:24px;margin:0}.feature .tile-number{font-size:8px}.feature h3{font-size:21px;margin:6px 0}.feature p{font-size:11px;margin:0;max-width:90%}.card-arrow{font-size:20px;bottom:20px;right:15px}.geometry{margin:30px 0}.model-grid{gap:14px}.model-caption{padding:18px;gap:20px}.model-caption p{font-size:10px}.model-caption h3{font-size:22px}.ai-banner{padding:22px;margin:25px 0}.closing{padding:30px 0}.closing h2{font-size:26px}.article h1,.directory h1{font-size:35px}.article main>p{font-size:14px;padding:18px}.article h2{font-size:25px}.directory main>a{padding:20px;font-size:15px}.directory .practice-choices{display:flex!important;flex-direction:column;gap:16px}.practice-choice{padding:24px!important}.choice-icon{padding:20px 0!important;font-size:33px!important}.practice-choice h2{font-size:27px}.choice-tag{font-size:8px!important}.practice-guide>div{grid-template-columns:1fr;gap:0}.practice-guide p{padding:13px 0;margin:0}.practice-guide .note{padding:15px;margin-top:12px}.page-intro{font-size:13px}.practice-heading{align-items:start;gap:10px;margin-bottom:25px}.practice-heading h1{font-size:29px;max-width:250px}.practice-heading .eyebrow{font-size:8px;margin-bottom:9px}.quiet-link{font-size:10px;white-space:nowrap;margin-top:4px}.quiz-layout{display:flex;flex-direction:column;gap:22px}.quiz-main{width:100%}.attempt-progress{font-size:10px}.exam-card{padding:22px 18px;border-radius:14px}.exam-card h2{font-size:23px;line-height:1.5;margin:14px 0 24px}.question-label{font-size:8px}.answer-option{padding:14px 12px;gap:12px;font-size:14px;min-height:58px}.option-badge{width:28px;height:28px}.answer-tools{font-size:9px;align-items:start}.clear-answer{padding:0;font-size:10px;min-height:30px}.question-controls{position:sticky;bottom:calc(68px + env(safe-area-inset-bottom));z-index:10;background:var(--paper);padding:15px 0 10px;border-bottom:1px solid var(--line);margin-top:10px}.question-controls .primary-button,.question-controls .secondary-button{font-size:11px;padding:11px 15px}.desktop-word{display:none}.position-count{font-size:10px}.question-map{width:100%;position:static;padding:22px 18px}.question-grid{grid-template-columns:repeat(5,1fr);gap:10px}.map-button{aspect-ratio:auto;min-height:42px;font-size:12px}.question-map .marking-note{display:none}.map-legend{justify-content:start;gap:20px;font-size:9px}.map-heading h2{font-size:23px}.submit-attempt{width:100%;min-height:46px}.dialog-actions{flex-direction:column-reverse}.submit-dialog{padding:26px}.result-hero{display:flex;flex-direction:column-reverse;gap:25px;padding:28px 22px;text-align:center}.score-orb{width:180px;height:180px}.score-orb strong{font-size:43px}.score-orb>span{font-size:8px}.result-hero h1{font-size:34px;margin:13px 0}.result-actions{justify-content:center}.result-stats{gap:8px;margin:18px 0 30px}.result-stats>div{padding:16px 9px;flex-direction:column;gap:5px}.result-stats strong{font-size:25px}.result-stats>div>span:last-child{font-size:10px}.result-stats .stat-dot{width:6px;height:6px}.review-item summary{padding:17px;gap:10px;flex-wrap:wrap;font-size:13px}.review-item summary>span:nth-child(2){flex:1;min-width:180px}.review-item .verdict{margin-left:23px;font-size:9px}.review-content{padding:20px}.answer-comparison{grid-template-columns:1fr;gap:0}.review-content>p{font-size:13px}.result-kicker{font-size:7px}}
@media(max-width:360px){.study-strip small{display:block;margin-left:0}.hero h1{font-size:42px}.brand{font-size:17px}.hero{padding:23px 19px}.practice-heading h1{font-size:25px}.question-controls .primary-button,.question-controls .secondary-button{padding:10px;font-size:10px}}
@media print{.desktop-rail,.mobile-dock,.question-controls,.question-map{display:none!important}body{padding:0}body>main,.article main{margin:0;width:100%;padding:0}.result-hero{background:white;box-shadow:none}.review-content{display:block}.review-item{break-inside:avoid}}
.directory .practice-choice .choice-facts span{padding:0;font:11px/1.5 'Segoe UI',Arial,sans-serif}.directory .practice-choice strong span{padding:0;font:18px/1 'Segoe UI',Arial,sans-serif}.directory .practice-choice .choice-icon{font-family:var(--serif)!important}.learning-note{border:1px solid var(--line);border-radius:14px;background:var(--surface-soft);padding:25px;margin:30px 0}.learning-note h2{font-size:25px!important;margin:0 0 18px!important}.learning-note ul{padding-left:20px;font-size:14px;line-height:1.9}.learning-note li{margin:10px 0}.learning-note p{font-size:14px;line-height:1.9;margin:0}
.directory main>div.practice-choices{grid-template-columns:repeat(2,minmax(0,1fr))}.directory h1{overflow-wrap:anywhere}.directory main>div>a{min-width:0}.directory main>div>a span{overflow-wrap:anywhere}@media(max-width:760px){.directory main>div.practice-choices{grid-template-columns:1fr}}
.article main{overflow-wrap:anywhere}.article main h1,.article main h2,.article main h3{overflow-wrap:anywhere}