:root{--paper:#faf9fc;--ink:#273344;--muted:#687282;--line:#e5e2eb;--lav:#eee8f7;--purple:#6e529f;--deep:#503d7a;--cyan:#e1f2f4;--teal:#197181;--green:#236554;--sidebar:270px}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--paper);color:var(--ink);font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;font-size:16px;line-height:1.65}button,input,textarea,select{font:inherit}button,a,input,textarea,summary{touch-action:manipulation}button{cursor:pointer;color:inherit}a{color:var(--deep);text-underline-offset:3px}button:disabled{cursor:default;opacity:.5}:focus-visible{outline:3px solid #299dad;outline-offset:4px}::selection{background:#e3d7f3}h1,h2,h3,h4,p{margin-top:0}h1,h2{font-family:Georgia,'Times New Roman',serif;font-weight:400;letter-spacing:-.035em;line-height:1.14}h1{font-size:clamp(35px,4vw,54px);margin-bottom:18px}h2{font-size:32px;margin-bottom:22px}h3{font-size:18px;line-height:1.35;margin-bottom:10px}h4{font-size:16px;line-height:1.4}p{margin-bottom:16px}.muted{color:var(--muted)}.eyebrow{font-size:11px;font-weight:700;text-transform:uppercase;letter-spacing:.16em;color:var(--purple);margin-bottom:13px}.skip{position:fixed;left:10px;top:-90px;z-index:20;background:white;padding:10px}.skip:focus{top:10px}.sidebar{width:var(--sidebar);position:fixed;inset:0 auto 0 0;background:#fff;border-right:1px solid var(--line);display:flex;flex-direction:column;z-index:5}.brand{padding:26px 24px 17px;text-decoration:none;display:flex;gap:12px;align-items:center;color:var(--ink)}.brand-symbol{width:36px;height:36px;border:1px solid #b3a0d0;border-radius:50%;display:grid;place-items:center;font-family:Georgia,serif;font-size:24px;color:var(--deep);background:var(--lav)}.brand-name{font-size:22px;letter-spacing:-.04em;font-family:Georgia,serif}.brand small{display:block;font-family:system-ui;font-size:9px;letter-spacing:.06em;color:var(--muted);margin-top:1px}.side-top{padding:0 16px 14px}.side-nav{display:grid;grid-template-columns:1fr 1fr;gap:5px;margin-bottom:12px}.nav-item{text-decoration:none;padding:8px 10px;border-radius:7px;font-size:12px;color:var(--muted)}.nav-item.current{color:var(--deep);background:var(--lav);font-weight:650}.search{display:flex;align-items:center;gap:8px;border:1px solid var(--line);border-radius:8px;padding:7px 10px;color:var(--muted);background:#faf9fc}.search input{width:100%;min-width:0;border:0;background:transparent;font-size:12px;outline:0}.search:focus-within{outline:2px solid var(--teal)}.course-menu{overflow-y:auto;padding:0 12px 22px;flex:1;scrollbar-width:thin}.chapter-label{font-size:10px;line-height:1.5;letter-spacing:.1em;text-transform:uppercase;padding:17px 12px 9px;color:var(--muted);font-weight:650}.lesson-link{display:flex;align-items:flex-start;gap:10px;text-decoration:none;padding:8px 10px;border-radius:8px;font-size:12px;line-height:1.5;color:#626c7b;margin-bottom:2px}.lesson-link:hover{background:#f5f2fa}.lesson-link.active{background:var(--lav);color:var(--deep);font-weight:600}.lesson-no{font-size:10px;line-height:19px;color:#9390a2;font-variant-numeric:tabular-nums;min-width:18px}.lesson-link.done .lesson-no{color:var(--green)}.side-bottom{padding:16px 23px;border-top:1px solid var(--line);font-size:11px;color:var(--muted);background:white}.progress-track{height:4px;background:#efedf4;border-radius:4px;overflow:hidden;margin:8px 0}.progress-track span{display:block;height:100%;background:#b4a0d2}.main-shell{margin-left:var(--sidebar);min-height:100vh}.topbar{height:65px;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;padding:0 42px;font-size:11px;color:var(--muted);background:var(--paper);gap:20px}.topbar span:first-of-type{letter-spacing:.06em}.session{border:1px solid var(--line);border-radius:30px;padding:3px 12px;color:#756787;white-space:nowrap}.menu-toggle{display:none;border:0;background:none;font-size:20px}.content{max-width:1120px;margin:auto;padding:42px 46px 70px}.page-head{margin-bottom:30px}.page-head .lead{font-size:17px;max-width:700px;line-height:1.7;color:#647081}.head-row{display:flex;justify-content:space-between;align-items:center;gap:16px}.tag{font-size:11px;color:var(--teal);background:var(--cyan);padding:4px 10px;border-radius:5px;display:inline-block}.tag.lav{color:var(--deep);background:var(--lav)}.course-hero{display:grid;grid-template-columns:1fr 165px;gap:35px;margin:15px 0 34px;border-bottom:1px solid var(--line);padding-bottom:34px}.hero-number{font-family:Georgia,serif;line-height:1;font-size:155px;color:#e1d8ef;text-align:right;letter-spacing:-.12em;margin-right:15px}.hero-stats{display:flex;gap:25px;flex-wrap:wrap;margin:22px 0;font-size:12px;color:var(--muted)}.hero-stats strong{font-family:Georgia,serif;font-size:24px;color:var(--ink);font-weight:400;display:block}.button,.secondary,.quiet{display:inline-flex;align-items:center;justify-content:center;gap:12px;padding:10px 19px;border:1px solid var(--deep);border-radius:7px;text-decoration:none;font-size:13px;font-weight:550;background:var(--deep);color:white;min-height:42px}.button:hover{background:#665089}.secondary{background:white;color:var(--deep);border-color:#d7cce6}.secondary:hover{background:#f2edf8}.quiet{border-color:transparent;color:var(--muted);background:transparent;padding:8px 3px}.button-row{display:flex;align-items:center;gap:16px;flex-wrap:wrap}.journey-note{font-size:13px;padding:17px 21px;border-left:3px solid #b5a3d0;background:#f0ebf7;margin:20px 0 36px}.chapter-block{margin:30px 0 44px}.chapter-heading{display:flex;align-items:center;gap:17px;margin-bottom:17px}.chapter-index{width:42px;height:42px;border:1px solid #cfc4df;border-radius:50%;display:grid;place-items:center;color:var(--deep);font-size:13px;background:#f3eff9}.chapter-heading h2{font-size:27px;margin:0 0 4px}.chapter-heading p{font-size:12px;margin:0;color:var(--muted)}.topic-list{background:white;border:1px solid var(--line);border-radius:14px;overflow:hidden}.topic-row{display:grid;grid-template-columns:36px 1fr auto;gap:12px;align-items:center;padding:14px 22px;border-bottom:1px solid #eeebf2;text-decoration:none;color:var(--ink)}.topic-row:last-child{border-bottom:0}.topic-row:hover{background:#f9f6fe}.topic-row .num{color:#a18bbd;font-size:12px}.topic-row b{font-weight:500;font-size:14px}.topic-row small{display:block;font-size:11px;color:var(--muted);margin-top:2px}.topic-row .status{font-size:10px;white-space:nowrap;color:var(--teal)}.stage-nav{display:flex;border-bottom:1px solid var(--line);margin:0 -2px 35px;gap:20px;overflow:auto;white-space:nowrap}.stage-tab{border:0;background:transparent;padding:12px 2px 15px;color:var(--muted);font-size:12px;border-bottom:2px solid transparent;display:flex;align-items:center;gap:8px;text-decoration:none}.stage-tab.active{color:var(--deep);border-bottom-color:var(--purple);font-weight:600}.stage-tab .dot{width:20px;height:20px;border-radius:50%;border:1px solid #d7d2df;display:grid;place-items:center;font-size:10px}.stage-tab.active .dot{background:var(--lav);border-color:#c9b7e2}.stage-tab.complete .dot{color:var(--green);background:#e7f1ed}.lesson-layout{display:grid;grid-template-columns:minmax(0,1fr) 184px;gap:34px}.lesson-body{min-width:0}.lesson-body .intro{font-family:Georgia,serif;font-size:23px;line-height:1.6;letter-spacing:-.012em;color:#404754;margin-bottom:30px}.lesson-body p{font-size:15px;line-height:1.85}.lesson-body section{margin:0 0 30px}.lesson-body section h3{font-size:17px}.lesson-aside{font-size:12px;color:var(--muted)}.aside-section{border-top:1px solid var(--line);padding-top:14px;margin-bottom:28px}.aside-section h4{font-size:10px;text-transform:uppercase;letter-spacing:.12em;color:#746880;margin-bottom:13px}.aside-section p{font-size:12px;line-height:1.8;margin-bottom:11px}.aside-section a{display:block;font-size:11px;margin-bottom:8px}.mini-path{padding-left:15px;margin:0;line-height:2.4;color:#857b91}.mini-path .on{color:var(--deep);font-weight:600}.foundation{border:1px solid #d7e8eb;background:#eef7f8;border-radius:10px;padding:13px 18px;margin-bottom:30px}.foundation summary{font-size:13px;font-weight:600;color:#2f7381;cursor:pointer}.foundation .bridge{padding-top:20px;border-top:1px solid #d6e6e9;margin-top:17px}.bridge p{font-size:14px}.bridge details{font-size:13px;margin-top:8px}.bridge summary{font-weight:500}.physics-figure,.graph-figure{margin:28px 0 31px;padding:20px 18px 15px;background:#f4f1f9;border:1px solid #e8e1f0;border-radius:11px}.physics-figure svg,.graph-figure svg{display:block;width:100%;height:auto;overflow:visible;font-family:system-ui}.physics-figure figcaption,.graph-figure figcaption{font-size:12px;line-height:1.7;color:#6a607b;padding:0 8px}.graph-figure{background:#fff;border-color:var(--line)}.graph-figure h4{font-size:14px;margin:0 8px 12px}.formula-list{border-top:1px solid var(--line)}.formula{padding:22px 0;border-bottom:1px solid var(--line)}.equation{font-family:Georgia,serif;font-size:22px;color:var(--deep);line-height:1.6;margin-bottom:9px;overflow-wrap:anywhere}.formula p{font-size:12px;line-height:1.75;margin-bottom:6px}.condition{color:var(--teal)}.reasoning{padding-left:0;list-style:none;counter-reset:reason}.reasoning li{counter-increment:reason;position:relative;padding:0 0 20px 43px;font-size:14px;line-height:1.85}.reasoning li:before{content:counter(reason);position:absolute;left:0;top:2px;width:25px;height:25px;border-radius:50%;background:var(--lav);color:var(--deep);display:grid;place-items:center;font-size:11px}.misconception{border-left:3px solid #bfaad9;background:#f3eff8;padding:20px 23px;font-size:14px;margin:30px 0}.misconception strong{display:block;font-size:11px;text-transform:uppercase;letter-spacing:.12em;color:var(--purple);margin-bottom:8px}.misconception p{margin:0 0 8px!important;font-size:14px}.misconception .wrong{color:#80728d;text-decoration:line-through;text-decoration-color:#bdaece}.stage-footer{display:flex;align-items:center;justify-content:space-between;border-top:1px solid var(--line);margin-top:35px;padding-top:24px;gap:16px}.stage-footer small{font-size:11px;color:var(--muted)}.question-box{padding:25px 28px;background:white;border:1px solid var(--line);border-radius:12px;margin:20px 0 30px}.question-box .question{font-family:Georgia,serif;font-size:22px;line-height:1.55;margin-bottom:22px}.question-box .eyebrow{margin-bottom:11px}.question-box p{font-size:14px}.steps li{margin-bottom:15px;padding-left:5px;font-size:14px;line-height:1.8}.hidden-step{padding:14px 18px;border:1px dashed #d9d2e2;border-radius:7px;margin:14px 0;color:#a398b0;font-size:12px}.input-label{display:block;font-size:12px;font-weight:600;margin:16px 0 7px}.answer-input{border:1px solid #cfc8d9;background:white;border-radius:7px;padding:10px 12px;max-width:100%;min-width:150px;width:220px;color:var(--ink)}.answer-area{display:block;min-height:135px;width:100%;resize:vertical;border:1px solid #d9d1e3;border-radius:8px;padding:15px;font-size:14px;line-height:1.75;color:var(--ink);background:#fdfcfe;margin-bottom:14px}.answer-area:focus{background:white}.option-list{display:grid;gap:9px;margin:15px 0 19px}.option{display:flex;align-items:flex-start;gap:10px;padding:11px 14px;border:1px solid var(--line);border-radius:8px;background:white;cursor:pointer;font-size:13px}.option:has(input:checked){background:#f2edf8;border-color:#b9a4d4}.option input{margin-top:5px;accent-color:var(--purple)}.feedback{font-size:13px;line-height:1.75;padding:13px 17px;background:var(--cyan);border-left:3px solid var(--teal);border-radius:0 7px 7px 0;margin:15px 0}.feedback.error{background:#fbefed;border-color:#b17166}.feedback.success{background:#eaf3ef;border-color:#568779}.hint{font-size:13px;margin:12px 0;color:var(--muted)}.hint summary{cursor:pointer;color:var(--teal)}.solution{border-top:1px solid var(--line);margin-top:22px;padding-top:22px}.checklist{list-style:none;padding:0;margin:20px 0}.checklist li{margin-bottom:12px}.checklist label{display:flex;gap:12px;align-items:flex-start;font-size:14px;line-height:1.75;cursor:pointer}.checklist input{margin-top:6px;accent-color:var(--purple)}.tiny-note{font-size:11px!important;color:var(--muted);line-height:1.6!important}.recall-prompt{font-size:21px!important;font-family:Georgia,serif;line-height:1.55!important}.complete-banner{padding:25px;border:1px solid #c3ded4;background:#edf5f1;border-radius:10px;margin:26px 0}.complete-banner h3{color:var(--green)}.filterbar{display:flex;flex-wrap:wrap;gap:8px;margin:23px 0}.filter{border:1px solid var(--line);border-radius:30px;padding:7px 14px;font-size:12px;background:white;color:var(--muted);text-decoration:none}.filter.active{color:var(--deep);background:var(--lav);border-color:#c7b7dc}.bank-card{border-top:1px solid var(--line);padding:25px 0}.bank-card h3{font-family:Georgia,serif;font-size:23px;font-weight:400;margin-bottom:12px}.bank-card p{font-size:14px}.bank-card .bank-meta{font-size:10px;color:var(--purple);text-transform:uppercase;letter-spacing:.09em;margin-bottom:10px}.bank-card details{margin-top:16px}.bank-card summary{font-size:13px;color:var(--deep);cursor:pointer}.question-parts{padding-left:24px;font-size:14px;line-height:1.8}.question-parts li{padding-left:5px;margin-bottom:11px}.topic-tags{display:flex;gap:8px;flex-wrap:wrap;margin-top:14px}.topic-tags a{font-size:10px;padding:2px 8px;border:1px solid var(--line);border-radius:4px;text-decoration:none;color:var(--muted)}.source-card{padding:22px 0;border-top:1px solid var(--line)}.source-card p{font-size:13px;margin-bottom:10px}.summary-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px;margin:28px 0}.summary-grid article{padding:23px;background:white;border:1px solid var(--line);border-radius:10px}.summary-grid strong{font-family:Georgia,serif;font-size:34px;font-weight:400;color:var(--deep);display:block}.summary-grid span{font-size:12px;color:var(--muted)}.coverage-table{width:100%;border-collapse:collapse;font-size:12px;background:white}.coverage-table th,.coverage-table td{text-align:left;border-bottom:1px solid var(--line);padding:12px}.coverage-table th{font-size:10px;text-transform:uppercase;letter-spacing:.06em;background:#f1edf6;color:var(--deep)}.table-wrap{overflow:auto;border:1px solid var(--line);border-radius:10px}.lab{background:#edf6f7;border:1px solid #cfe5e9;padding:24px;border-radius:12px;margin:28px 0}.lab h3{color:#2c727f}.lab p{font-size:13px}.lab label{display:block;font-size:12px;margin:15px 0 5px}.lab input[type=range]{width:100%;accent-color:var(--teal)}.lab select{border:1px solid #bad7df;border-radius:5px;padding:8px;background:white;width:100%;font-size:12px}.lab-result{font-family:Georgia,serif;font-size:23px;color:var(--teal);margin:14px 0 9px}.lab-result small{font-family:system-ui;font-size:12px}.memory-map{display:grid;grid-template-columns:repeat(2,1fr);gap:20px}.memory-map article{border-top:2px solid #bfacd9;background:white;padding:22px}.memory-map h3{font-size:16px}.memory-map p{font-size:13px;margin-bottom:10px}.notice{padding:15px 20px;background:var(--cyan);border-radius:9px;font-size:13px;margin-bottom:25px}.empty{padding:40px 20px;text-align:center;color:var(--muted)}.storage-warning{padding:8px 20px;background:#faefe0;font-size:12px}.overlay{display:none}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}.page-foot{border-top:1px solid var(--line);padding:25px 46px;color:#8d8299;font-size:10px;display:flex;justify-content:space-between;gap:14px}.loading{padding:60px}.toast{position:fixed;bottom:25px;right:25px;background:var(--ink);color:white;padding:12px 20px;border-radius:8px;font-size:13px;z-index:30;max-width:calc(100vw - 35px)}
@media(min-width:1500px){:root{--sidebar:290px}.content{padding-top:55px}.lesson-body p{font-size:16px}.lesson-link{font-size:13px}}
@media(max-width:1180px){:root{--sidebar:245px}.content{padding:35px 32px 60px}.lesson-layout{grid-template-columns:minmax(0,1fr)}.lesson-aside{display:grid;grid-template-columns:1fr 1fr;gap:22px}.aside-section{margin-bottom:0}.lesson-aside .path-section{display:none}.topbar{padding:0 32px}.hero-number{font-size:130px}.course-hero{grid-template-columns:1fr 130px}.stage-nav{gap:17px}}
@media(max-width:800px){.sidebar{transform:translateX(-100%);transition:transform .2s}.menu-open .sidebar{transform:translateX(0)}.menu-open .overlay{display:block;position:fixed;inset:0;background:#24213355;z-index:4;border:0}.main-shell{margin-left:0}.menu-toggle{display:block}.topbar{padding:0 22px;height:58px;justify-content:flex-start;gap:15px}.session{margin-left:auto}.content{padding:30px 24px 50px}.course-hero{grid-template-columns:1fr 100px;gap:14px}.hero-number{font-size:105px}.page-foot{padding:22px 24px}.question-box{padding:23px}.stage-nav{gap:22px}.stage-tab{font-size:11px}.memory-map{grid-template-columns:1fr}.summary-grid{gap:9px}.summary-grid article{padding:16px}.summary-grid strong{font-size:27px}}
@media(max-width:480px){.course-hero{display:block}.hero-number{display:none}.hero-stats{gap:21px}.content{padding-left:19px;padding-right:19px}.lesson-body .intro{font-size:21px}.question-box{padding:19px}.question-box .question{font-size:20px}.topic-row{padding:13px 15px;grid-template-columns:25px 1fr auto;gap:8px}.topic-row small{font-size:10px}.topic-row .status{max-width:62px;white-space:normal;text-align:right}.lesson-aside{grid-template-columns:1fr}.stage-footer{align-items:flex-start}.stage-footer .button{max-width:70%;text-align:center}.physics-figure,.graph-figure{padding:14px 5px}.physics-figure figcaption,.graph-figure figcaption{padding:4px 10px}.session{font-size:10px;padding:2px 8px}.summary-grid{grid-template-columns:1fr 1fr}.summary-grid article:last-child{grid-column:span 2}.equation{font-size:20px}.stage-nav{margin-right:-19px}.page-foot{flex-direction:column}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*:before,*:after{transition:none!important;animation:none!important}}
@media print{.sidebar,.topbar,.stage-nav,.stage-footer,.page-foot,.button,.secondary,.quiet,.filterbar,.lab{display:none!important}.main-shell{margin:0}.content{max-width:none;padding:0}.lesson-layout{display:block}.lesson-aside{display:none}body{background:white;font-size:11pt}.question-box,.physics-figure,.formula{break-inside:avoid}.answer-area{min-height:100px}}
@media(max-width:800px){.lesson-link,.nav-item{min-height:44px;align-items:center}.option{min-height:44px}.filter{min-height:40px}}
