@font-face{font-family:Geist;font-style:normal;font-weight:100 900;font-display:swap;src:url(../media/fef07dbb0973bf53-s.12tyk43_3sh9u.woff2)format("woff2");unicode-range:U+460-52F,U+1C80-1C8A,U+20B4,U+2DE0-2DFF,U+A640-A69F,U+FE2E-FE2F}@font-face{font-family:Geist;font-style:normal;font-weight:100 900;font-display:swap;src:url(../media/8a480f0b521d4e75-s.0jzbimsg8vl84.woff2)format("woff2");unicode-range:U+301,U+400-45F,U+490-491,U+4B0-4B1,U+2116}@font-face{font-family:Geist;font-style:normal;font-weight:100 900;font-display:swap;src:url(../media/53b9e256198e5412-s.0-wfv7uh4i7h9.woff2)format("woff2");unicode-range:U+102-103,U+110-111,U+128-129,U+168-169,U+1A0-1A1,U+1AF-1B0,U+300-301,U+303-304,U+308-309,U+323,U+329,U+1EA0-1EF9,U+20AB}@font-face{font-family:Geist;font-style:normal;font-weight:100 900;font-display:swap;src:url(../media/7178b3e590c64307-s.0nx0ww8fni_q3.woff2)format("woff2");unicode-range:U+100-2BA,U+2BD-2C5,U+2C7-2CC,U+2CE-2D7,U+2DD-2FF,U+304,U+308,U+329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF}@font-face{font-family:Geist;font-style:normal;font-weight:100 900;font-display:swap;src:url(../media/caa3a2e1cccd8315-s.p.09~u27dqhyhd6.woff2)format("woff2");unicode-range:U+??,U+131,U+152-153,U+2BB-2BC,U+2C6,U+2DA,U+2DC,U+304,U+308,U+329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD}@font-face{font-family:Geist Fallback;src:local(Arial);ascent-override:95.94%;descent-override:28.16%;line-gap-override:0.0%;size-adjust:104.76%}.geist_a71539c9-module__T19VSG__className{font-family:Geist,Geist Fallback;font-style:normal}.geist_a71539c9-module__T19VSG__variable{--font-geist-sans:"Geist", "Geist Fallback"}
@font-face{font-family:Geist Mono;font-style:normal;font-weight:100 900;font-display:swap;src:url(../media/5ce348bf30bf5439-s.0zgw-jeven.3w.woff2)format("woff2");unicode-range:U+460-52F,U+1C80-1C8A,U+20B4,U+2DE0-2DFF,U+A640-A69F,U+FE2E-FE2F}@font-face{font-family:Geist Mono;font-style:normal;font-weight:100 900;font-display:swap;src:url(../media/4fa387ec64143e14-s.0wkzw~je483f-.woff2)format("woff2");unicode-range:U+301,U+400-45F,U+490-491,U+4B0-4B1,U+2116}@font-face{font-family:Geist Mono;font-style:normal;font-weight:100 900;font-display:swap;src:url(../media/6306c77e7c8268e4-s.0rhz0arwfsn~5.woff2)format("woff2");unicode-range:U+2000-2001,U+2004-2008,U+200A,U+23B8-23BD,U+2500-259F}@font-face{font-family:Geist Mono;font-style:normal;font-weight:100 900;font-display:swap;src:url(../media/7d817b4c03b0c5f1-s.0l76wvqk9d84w.woff2)format("woff2");unicode-range:U+102-103,U+110-111,U+128-129,U+168-169,U+1A0-1A1,U+1AF-1B0,U+300-301,U+303-304,U+308-309,U+323,U+329,U+1EA0-1EF9,U+20AB}@font-face{font-family:Geist Mono;font-style:normal;font-weight:100 900;font-display:swap;src:url(../media/bbc41e54d2fcbd21-s.0k4k9394f2q-k.woff2)format("woff2");unicode-range:U+100-2BA,U+2BD-2C5,U+2C7-2CC,U+2CE-2D7,U+2DD-2FF,U+304,U+308,U+329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF}@font-face{font-family:Geist Mono;font-style:normal;font-weight:100 900;font-display:swap;src:url(../media/797e433ab948586e-s.p.08e28id.o-okb.woff2)format("woff2");unicode-range:U+??,U+131,U+152-153,U+2BB-2BC,U+2C6,U+2DA,U+2DC,U+304,U+308,U+329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD}@font-face{font-family:Geist Mono Fallback;src:local(Arial);ascent-override:74.67%;descent-override:21.92%;line-gap-override:0.0%;size-adjust:134.59%}.geist_mono_8d43a2aa-module__8Li5zG__className{font-family:Geist Mono,Geist Mono Fallback;font-style:normal}.geist_mono_8d43a2aa-module__8Li5zG__variable{--font-geist-mono:"Geist Mono", "Geist Mono Fallback"}
@layer properties{@supports (((-webkit-hyphens:none)) and (not (margin-trim:inline))) or ((-moz-orient:inline) and (not (color:rgb(from red r g b)))){*,:before,:after,::backdrop{--tw-ordinal:initial;--tw-slashed-zero:initial;--tw-numeric-figure:initial;--tw-numeric-spacing:initial;--tw-numeric-fraction:initial}}}@layer theme{:root,:host{--font-sans:ui-sans-serif, system-ui, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";--font-mono:ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;--spacing:.25rem;--default-font-family:var(--font-sans);--default-mono-font-family:var(--font-mono)}}@layer base{*,:after,:before,::backdrop{box-sizing:border-box;border:0 solid;margin:0;padding:0}::file-selector-button{box-sizing:border-box;border:0 solid;margin:0;padding:0}html,:host{-webkit-text-size-adjust:100%;tab-size:4;line-height:1.5;font-family:var(--default-font-family,ui-sans-serif, system-ui, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji");font-feature-settings:var(--default-font-feature-settings,normal);font-variation-settings:var(--default-font-variation-settings,normal);-webkit-tap-highlight-color:transparent}hr{height:0;color:inherit;border-top-width:1px}abbr:where([title]){-webkit-text-decoration:underline dotted;text-decoration:underline dotted}h1,h2,h3,h4,h5,h6{font-size:inherit;font-weight:inherit}a{color:inherit;-webkit-text-decoration:inherit;-webkit-text-decoration:inherit;-webkit-text-decoration:inherit;-webkit-text-decoration:inherit;text-decoration:inherit}b,strong{font-weight:bolder}code,kbd,samp,pre{font-family:var(--default-mono-font-family,ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace);font-feature-settings:var(--default-mono-font-feature-settings,normal);font-variation-settings:var(--default-mono-font-variation-settings,normal);font-size:1em}small{font-size:80%}sub,sup{vertical-align:baseline;font-size:75%;line-height:0;position:relative}sub{bottom:-.25em}sup{top:-.5em}table{text-indent:0;border-color:inherit;border-collapse:collapse}:-moz-focusring{outline:auto}progress{vertical-align:baseline}summary{display:list-item}ol,ul,menu{list-style:none}img,svg,video,canvas,audio,iframe,embed,object{vertical-align:middle;display:block}img,video{max-width:100%;height:auto}button,input,select,optgroup,textarea{font:inherit;font-feature-settings:inherit;font-variation-settings:inherit;letter-spacing:inherit;color:inherit;opacity:1;background-color:#0000;border-radius:0}::file-selector-button{font:inherit;font-feature-settings:inherit;font-variation-settings:inherit;letter-spacing:inherit;color:inherit;opacity:1;background-color:#0000;border-radius:0}:where(select:is([multiple],[size])) optgroup{font-weight:bolder}:where(select:is([multiple],[size])) optgroup option{padding-inline-start:20px}::file-selector-button{margin-inline-end:4px}::placeholder{opacity:1}@supports (not ((-webkit-appearance:-apple-pay-button))) or (contain-intrinsic-size:1px){::placeholder{color:currentColor}@supports (color:color-mix(in lab, red, red)){::placeholder{color:color-mix(in oklab, currentcolor 50%, transparent)}}}textarea{resize:vertical}::-webkit-search-decoration{-webkit-appearance:none}::-webkit-date-and-time-value{min-height:1lh;text-align:inherit}::-webkit-datetime-edit{display:inline-flex}::-webkit-datetime-edit-fields-wrapper{padding:0}::-webkit-datetime-edit{padding-block:0}::-webkit-datetime-edit-year-field{padding-block:0}::-webkit-datetime-edit-month-field{padding-block:0}::-webkit-datetime-edit-day-field{padding-block:0}::-webkit-datetime-edit-hour-field{padding-block:0}::-webkit-datetime-edit-minute-field{padding-block:0}::-webkit-datetime-edit-second-field{padding-block:0}::-webkit-datetime-edit-millisecond-field{padding-block:0}::-webkit-datetime-edit-meridiem-field{padding-block:0}::-webkit-calendar-picker-indicator{line-height:1}:-moz-ui-invalid{box-shadow:none}button,input:where([type=button],[type=reset],[type=submit]){appearance:button}::file-selector-button{appearance:button}::-webkit-inner-spin-button{height:auto}::-webkit-outer-spin-button{height:auto}[hidden]:where(:not([hidden=until-found])){display:none!important}}@layer components;@layer utilities{.relative{position:relative}.start{inset-inline-start:var(--spacing)}.m-1{margin:calc(var(--spacing) * 1)}.block{display:block}.table{display:table}.ordinal{--tw-ordinal:ordinal;font-variant-numeric:var(--tw-ordinal,) var(--tw-slashed-zero,) var(--tw-numeric-figure,) var(--tw-numeric-spacing,) var(--tw-numeric-fraction,)}}:root{--ink:#1d1d1f;--muted:#6e6e73;--soft:#f5f5f7;--paper:#fff;--white:#fff;--line:#d2d2d7;--blue:#0071e3;--blue-hover:#0077ed;--blue-soft:#e8f2ff;--indigo:#5856d6;--green:#248a3d;--orange:#a34b00;--red:#d70015;--glass:#fffc;--apple-shadow:0 12px 36px #0000000f;--apple-shadow-raised:0 22px 60px #00000017;--ease-apple:cubic-bezier(.28,.11,.32,1)}*{box-sizing:border-box}html{scroll-behavior:smooth}body{color:var(--ink);background:var(--paper);font-family:-apple-system, BlinkMacSystemFont, "SF Pro Text", "SF Pro Display", var(--font-geist-sans), "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;text-rendering:optimizelegibility;font-synthesis:none;margin:0}::selection{color:#fff;background:var(--blue)}button,input{font:inherit}button{color:inherit}code,pre{font-family:var(--font-geist-mono), "SFMono-Regular", Consolas, monospace}h1,h2,h3,h4,strong,b{font-family:-apple-system, BlinkMacSystemFont, "SF Pro Display", var(--font-geist-sans), "PingFang SC", "Microsoft YaHei", sans-serif}.topbar{z-index:60;background:var(--glass);-webkit-backdrop-filter:blur(28px)saturate(180%);backdrop-filter:blur(28px)saturate(180%);border-bottom:1px solid #00000014;grid-template-columns:1fr auto 1fr;align-items:center;height:62px;padding:0 4vw;display:grid;position:sticky;top:0}.brand{cursor:pointer;text-align:left;background:0 0;border:0;align-items:center;gap:11px;width:max-content;display:flex}.brand-mark{color:#fff;background:var(--ink);letter-spacing:-.06em;border-radius:10px;place-items:center;width:34px;height:34px;font-weight:700;display:grid;box-shadow:0 5px 16px #0000001f}.brand b,.brand small{display:block}.brand b{letter-spacing:-.01em;font-size:13px;font-weight:600}.brand small{color:var(--muted);letter-spacing:.04em;margin-top:2px;font-size:10px}.topbar nav{gap:2px;display:flex}.topbar nav button{cursor:pointer;transition:background .25s var(--ease-apple), color .25s var(--ease-apple), transform .25s var(--ease-apple);background:0 0;border:0;border-radius:999px;padding:8px 13px;font-size:12px;font-weight:500}.topbar nav button:hover{background:#0000000d}.topbar nav button:active{transform:scale(.97)}.topbar nav button.active{color:#fff;background:var(--ink);box-shadow:0 3px 12px #00000024}.progress-pill{border:1px solid var(--line);border-radius:999px;justify-self:end;align-items:baseline;gap:5px;padding:7px 10px;display:flex}.progress-pill b{font-size:12px}.progress-pill span{color:var(--muted);font-size:9px}.hero{text-align:center;background:radial-gradient(circle at 50% 34%,#0071e313,#0000 30%),linear-gradient(#fff 0%,#fbfbfd 100%);flex-direction:column;align-items:center;min-height:760px;padding:132px 8vw 64px;display:flex}.eyebrow,.section-label{color:var(--blue);letter-spacing:.14em;text-transform:uppercase;margin:0 0 18px;font-size:10px;font-weight:600;line-height:1.2}.hero h1,.page-shell>h1{text-wrap:balance;max-width:1180px;margin:0;font-weight:650}.hero h1{letter-spacing:-.04em;max-width:900px;font-size:clamp(42px,5.3vw,76px);line-height:1.04}.page-shell>h1{letter-spacing:-.05em;font-size:clamp(44px,6.5vw,88px);line-height:1}.hero h1 span,.page-shell>h1 span{color:#86868b}.hero-copy,.page-intro{max-width:760px;color:var(--muted);letter-spacing:-.012em;margin:32px auto 0;font-size:17px;line-height:1.68}.hero-actions{gap:10px;margin-top:36px;display:flex}.hero-actions button{cursor:pointer;transition:transform .25s var(--ease-apple), background .25s var(--ease-apple), box-shadow .25s var(--ease-apple);border:0;border-radius:999px;padding:13px 21px;font-size:13px;font-weight:500}.hero-actions button:hover{transform:translateY(-1px)}.hero-actions button:active{transform:scale(.98)}.primary{color:#fff;background:var(--blue)}.primary:hover{background:var(--blue-hover);box-shadow:0 7px 20px #0071e333}.secondary{background:#f5f5f7eb;box-shadow:inset 0 1px #ffffffe6;border:1px solid #0000000f!important}.secondary:hover{background:#e8e8ed}.hero-stats{border-top:1px solid var(--line);text-align:left;grid-template-columns:repeat(4,1fr);width:min(1200px,100%);margin-top:auto;display:grid}.hero-stats div{padding:26px 22px 0}.hero-stats strong,.hero-stats span{display:block}.hero-stats strong{letter-spacing:-.04em;font-size:28px}.hero-stats span{color:var(--muted);margin-top:5px;font-size:11px}.north-star{color:#f5f5f7;background:var(--ink);grid-template-columns:.85fr 1.15fr;gap:8vw;padding:120px 8vw;display:grid}.north-star h2{letter-spacing:-.05em;margin:0;font-size:clamp(34px,4.2vw,58px);line-height:1.08}.north-star ol{border-top:1px solid #38383e;margin:0;padding:0;list-style:none}.north-star li{border-bottom:1px solid #38383e;grid-template-columns:46px 1fr;gap:12px;padding:18px 0;display:grid}.north-star li span{color:#7db1ff;font:600 10px/1.8 var(--font-geist-mono), monospace}.north-star li p{color:#a9a9af;margin:0;line-height:1.55}.north-star li b{color:#fff}.reader-shell{max-width:1240px;margin:0 auto;padding:100px 5vw 150px;display:block}.module-rail{display:none}.rail-title{color:var(--muted);border-bottom:1px solid var(--line);letter-spacing:.13em;justify-content:space-between;padding:0 10px 14px;font-size:9px;display:flex}.module-rail>button{cursor:pointer;text-align:left;background:0 0;border:0;border-radius:13px;grid-template-columns:34px 1fr;align-items:center;gap:11px;width:100%;padding:10px;display:grid}.module-rail>button:hover,.module-rail>button.selected{background:#fff;box-shadow:0 1px #0000000a}.week-dot{border:1px solid var(--line);width:31px;height:31px;color:var(--muted);border-radius:50%;place-items:center;font-size:11px;display:grid}.week-dot.done{color:#fff;border-color:var(--blue);background:var(--blue)}.module-rail b,.module-rail small{display:block}.module-rail b{font-size:13px}.module-rail small{color:var(--muted);margin-top:2px;font-size:9px}.module-content{min-width:0}.week-switcher{background:var(--soft);border-radius:18px;justify-content:space-between;align-items:center;gap:18px;margin-bottom:38px;padding:8px 10px 8px 16px;display:flex}.week-switcher>span{color:var(--muted);letter-spacing:.08em;flex:none;font-size:10px;font-weight:600}.week-switcher>div{scrollbar-width:none;gap:4px;display:flex;overflow-x:auto}.week-switcher>div::-webkit-scrollbar{display:none}.week-switcher button{width:34px;height:34px;color:var(--muted);cursor:pointer;transition:color .2s var(--ease-apple), background .2s var(--ease-apple), transform .2s var(--ease-apple);background:0 0;border:0;border-radius:50%;flex:0 0 34px;font-size:11px}.week-switcher button:hover{color:var(--ink);background:#fff}.week-switcher button:active{transform:scale(.95)}.week-switcher button.done{color:var(--blue)}.week-switcher button.active{color:#fff;background:var(--ink)}.module-heading{border-bottom:1px solid var(--line);justify-content:space-between;align-items:flex-start;gap:24px;padding-bottom:32px;display:flex}.module-heading h2{letter-spacing:-.055em;margin:0;font-size:clamp(40px,5vw,68px);line-height:1.03}.english{color:var(--muted);margin:9px 0 0;font-size:16px}.coverage{letter-spacing:.08em;border-radius:999px;padding:5px 7px;display:inline-block}.coverage.slides{color:var(--green);background:#e4f5ec}.coverage.guide{color:var(--orange);background:#fff0d9}.coverage.mixed{color:var(--indigo);background:#efefff}.done-button{border:1px solid var(--line);cursor:pointer;white-space:nowrap;background:#fff;border-radius:999px;padding:9px 13px;font-size:11px}.done-button.checked{color:#fff;border-color:var(--blue);background:var(--blue)}.source-line{color:#8b8b91;margin:13px 0 0;font-size:10px}.textbook-note{box-shadow:var(--apple-shadow);background:linear-gradient(135deg,#fffffff0,#eef5ff);border:1px solid #d9e5f8;border-radius:20px;margin-top:18px;padding:20px 22px}.textbook-note div{justify-content:space-between;align-items:baseline;gap:16px;display:flex}.textbook-note small{color:var(--blue);letter-spacing:.12em;font-size:8px;font-weight:600}.textbook-note b{font-size:11px}.textbook-note p{color:#3f4d60;margin:10px 0 0;font-size:12px;line-height:1.6}.textbook-note .source-boundary{color:#697688;border-top:1px solid #d9e5f8;padding-top:9px;font-size:10px}.simple-card{color:#fff;box-shadow:var(--apple-shadow-raised);background:linear-gradient(145deg,#1d1d1f,#2c2c2e);border-radius:28px;margin:34px 0 70px;padding:34px}.simple-card small{color:#8bb8ff;letter-spacing:.12em;font-size:10px}.simple-card p{letter-spacing:-.025em;margin:12px 0 0;font-size:clamp(20px,2.5vw,30px);line-height:1.5}.first-question{margin-bottom:72px}.first-question h3{letter-spacing:-.04em;max-width:900px;margin:0;font-size:clamp(26px,3.3vw,42px);line-height:1.22}.section-head{justify-content:space-between;align-items:end;gap:24px;margin-bottom:30px;display:flex}.section-head h3{letter-spacing:-.03em;margin:0;font-size:clamp(27px,2.6vw,36px);font-weight:600;line-height:1.15}.decision-card h3,.trap-card h3,.memory-line p{letter-spacing:-.035em;margin:0;font-size:26px}.section-head>span{color:var(--muted);background:var(--soft);border-radius:999px;flex:none;padding:8px 12px;font-size:10px}.concept-list{gap:14px;margin-top:38px;display:grid}.concept-card{background:var(--soft);transition:background .3s var(--ease-apple), box-shadow .3s var(--ease-apple), transform .3s var(--ease-apple);border:0;border-radius:28px;overflow:hidden}.concept-card:last-child{border:0}.concept-card:hover{background:#f0f0f2}.concept-card.open{box-shadow:var(--apple-shadow-raised);background:#f0f0f2}.concept-head{text-align:left;cursor:pointer;background:0 0;border:0;grid-template-columns:42px minmax(0,1fr) 38px;align-items:center;gap:18px;width:100%;padding:27px 28px;display:grid}.concept-head:focus-visible{outline-offset:-3px;outline:3px solid #0071e359}.concept-head>span{width:38px;height:38px;color:var(--blue);font:600 10px/1 var(--font-geist-mono), monospace;transition:color .25s var(--ease-apple), background .25s var(--ease-apple);background:#fff;border:1px solid #0071e329;border-radius:50%;place-items:center;display:grid}.concept-card.open .concept-head>span{color:#fff;border-color:var(--blue);background:var(--blue)}.concept-head h3{letter-spacing:-.02em;margin:0;font-size:21px;font-weight:600;line-height:1.25}.concept-head p{max-width:970px;color:var(--muted);margin:7px 0 0;font-size:13px;line-height:1.58}.concept-head i{width:36px;height:36px;color:var(--ink);background:#fff;border-radius:50%;place-items:center;font-size:19px;font-style:normal;font-weight:300;display:grid;box-shadow:0 1px 2px #0000000a}.concept-body{box-shadow:none;background:#fff;border:0;border-radius:23px;margin:0 14px 14px;padding:32px 34px 34px}.why-block{background:var(--blue-soft);border-radius:20px;padding:22px 24px}.why-block small,.concept-foundation small,.application-block small{color:var(--blue);letter-spacing:.1em;margin-bottom:9px;font-size:9px;font-weight:600;display:block}.why-block p{color:#2f3e52;margin:0;font-size:14px;line-height:1.75}.concept-foundation{background:var(--soft);border-radius:20px;margin-top:14px;padding:22px 24px}.concept-foundation ul{gap:12px;margin:0;padding:0;list-style:none;display:grid}.concept-foundation li{margin:0;padding-left:18px;font-size:14px;line-height:1.65;position:relative}.concept-foundation li:before{content:"";background:var(--blue);border-radius:50%;width:5px;height:5px;position:absolute;top:.72em;left:0}.deep-dive{background:var(--soft);border:0;border-radius:23px;margin-top:28px;overflow:hidden}.deep-label{color:var(--ink);background:var(--soft);justify-content:space-between;align-items:center;gap:18px;padding:20px 24px;display:flex}.deep-label span{color:var(--blue);letter-spacing:.14em;font-size:9px;font-weight:600}.deep-label b{color:var(--muted);font-size:12px;font-weight:500}.deep-dive small{color:var(--blue);letter-spacing:.12em;margin-bottom:8px;font-size:8px;font-weight:600;display:block}.intuition-block,.mechanism-block{padding:25px 26px}.intuition-block p,.deep-two-up p{color:#3a3a3c;margin:0;font-size:14px;line-height:1.75}.intuition-block{background:#fff;border-top:1px solid #e8e8ed}.mechanism-block{background:#fbfbfd;border-top:1px solid #e8e8ed}.mechanism-block ol{counter-reset:deep-step;margin:0;padding:0;list-style:none}.mechanism-block li{counter-increment:deep-step;color:#3a3a3c;grid-template-columns:28px 1fr;gap:12px;margin:12px 0;line-height:1.6;display:grid}.mechanism-block li:before{content:counter(deep-step);width:24px;height:24px;color:var(--blue);background:var(--blue-soft);font:700 9px/1 var(--font-geist-mono), monospace;border-radius:50%;place-items:center;display:grid}.deep-two-up{background:#e8e8ed;grid-template-columns:1fr 1fr;gap:1px;display:grid}.deep-two-up>div{background:#fff;padding:25px 26px}.deep-two-up>div+div{background:#fff;border-left:0}.deep-two-up p{font-size:13px}.application-block{background:var(--blue-soft);border-top:1px solid #e8e8ed;padding:25px 26px}.application-block p{color:#2f3e52;margin:0;font-size:13px;line-height:1.7}.formula-box,.code-box{background:var(--soft);border-radius:18px;margin-top:16px;padding:20px 22px}.formula-box small,.code-box small{color:var(--blue);letter-spacing:.13em;margin-bottom:8px;font-size:8px;font-weight:600;display:block}.formula-box code{font-size:13px}.code-box{color:#ddd;background:#111116}.code-box small{color:#8bb8ff}.code-box pre{white-space:pre-wrap;margin:0;font-size:11px;line-height:1.6}.example-note{color:var(--muted);background:#fff8e9;border-radius:18px;margin:16px 0 0;padding:18px 20px;font-size:13px;line-height:1.6}.two-up{grid-template-columns:1.2fr .8fr;gap:20px;margin-top:80px;display:grid}.decision-card,.trap-card{border-radius:25px;padding:28px}.decision-card{background:#fff}.decision-card ol{margin:24px 0 0;padding:0;list-style:none}.decision-card li{border-top:1px solid var(--line);grid-template-columns:30px 1fr;gap:10px;padding:12px 0;display:grid}.decision-card li span{color:var(--blue);font-size:10px;font-weight:600}.decision-card li p{margin:0;font-size:13px;line-height:1.5}.trap-card{background:#f1eee8}.trap-card ul{margin:24px 0 0;padding:0;list-style:none}.trap-card li{border-top:1px solid #d9d3ca;padding:12px 0 12px 20px;font-size:13px;line-height:1.5;position:relative}.trap-card li:before{content:"×";color:var(--red);font-weight:800;position:absolute;left:0}.memory-line{color:#fff;background:var(--blue);border-radius:25px;margin-top:20px;padding:30px}.memory-line small{color:#c9ddff;letter-spacing:.12em;font-size:9px}.memory-line p{margin-top:10px}.page-shell{background:linear-gradient(#fff 0,#fbfbfd 600px);min-height:100vh;padding:120px 7vw 150px}.page-shell>.eyebrow{text-align:center}.page-shell>h1{text-align:center;margin:0 auto}.page-intro{text-align:center}.textbook-page{padding-left:5vw;padding-right:5vw}.book-stats{border:1px solid var(--line);background:var(--line);border-radius:25px;grid-template-columns:repeat(4,1fr);gap:1px;max-width:1120px;margin:70px auto 0;display:grid;overflow:hidden}.book-stats div{background:#fff;padding:25px}.book-stats strong,.book-stats span{display:block}.book-stats strong{letter-spacing:-.04em;font-size:29px}.book-stats span{color:var(--muted);letter-spacing:.08em;text-transform:uppercase;margin-top:5px;font-size:9px}.book-controls{border:1px solid var(--line);background:#ffffffd1;border-radius:20px;justify-content:space-between;align-items:end;gap:25px;max-width:1400px;margin:70px auto 25px;padding:18px 20px;display:flex}.book-controls label{flex:1;min-width:300px}.book-controls label span{color:var(--muted);margin-bottom:7px;font-size:9px;display:block}.book-controls input{background:0 0;border:0;outline:0;width:100%;font-size:17px}.book-controls>div{flex-wrap:wrap;justify-content:flex-end;gap:5px;display:flex}.book-controls button{border:1px solid var(--line);cursor:pointer;background:#fff;border-radius:999px;padding:7px 10px;font-size:9px}.book-controls button.active{color:#fff;border-color:var(--ink);background:var(--ink)}.book-controls .book-rail-toggle{color:var(--blue);background:var(--blue-soft);border-color:#0071e338}.book-controls .book-rail-toggle:hover{background:#dcecff}.book-shell{grid-template-columns:285px minmax(0,1fr);align-items:start;gap:55px;max-width:1400px;margin:0 auto;display:grid}.book-shell.rail-hidden{grid-template-columns:minmax(0,1fr);max-width:1180px}.book-rail{border:1px solid var(--line);scrollbar-width:thin;background:#fff;border-radius:22px;max-height:calc(100vh - 115px);padding:10px;position:sticky;top:90px;overflow:auto}.book-rail>div{color:var(--muted);border-bottom:1px solid var(--line);padding:10px 12px 14px}.book-rail>div small{letter-spacing:.12em;font-size:8px}.book-rail>button{text-align:left;cursor:pointer;background:0 0;border:0;border-radius:12px;grid-template-columns:31px 1fr;gap:10px;width:100%;padding:11px 10px;display:grid}.book-rail>button:hover,.book-rail>button.selected{background:var(--soft)}.book-rail>button>span{color:var(--blue);font:700 9px/1.6 var(--font-geist-mono), monospace}.book-rail b,.book-rail small{display:block}.book-rail b{font-size:11px;line-height:1.35}.book-rail button small{color:var(--muted);margin-top:3px;font-size:8px}.book-rail>p{color:var(--muted);padding:20px 12px;font-size:11px}.book-reader{min-width:0}.book-reader>header{color:#fff;box-shadow:var(--apple-shadow-raised);background:linear-gradient(145deg,#1d1d1f,#2c2c2e);border-radius:30px;padding:40px}.book-reader>header .section-label{color:#7db1ff}.book-reader>header>div{color:#8f8f97;font:650 9px/1.5 var(--font-geist-mono), monospace;letter-spacing:.1em;justify-content:space-between;gap:20px;display:flex}.book-reader>header h2{letter-spacing:-.05em;max-width:900px;margin:38px 0 0;font-size:clamp(37px,4.2vw,62px);line-height:1.06}.source-limited{color:#ffcf8c;background:#31271b;border-radius:999px;margin-top:22px;padding:7px 9px;font-size:9px;display:inline-block}.chapter-purpose{background:var(--blue);color:#fff;border-radius:24px;margin:18px 0 65px;padding:30px}.chapter-purpose small,.chapter-bridge small{color:#cce0ff;letter-spacing:.13em;font-size:8px;font-weight:600}.chapter-purpose p{letter-spacing:-.02em;margin:12px 0 0;font-size:clamp(18px,2vw,25px);line-height:1.55}.book-section-heading{justify-content:space-between;align-items:end;margin-bottom:20px;display:flex}.book-section-heading h3{letter-spacing:-.035em;margin:0;font-size:27px}.book-section-heading>span{color:var(--muted);font-size:9px}.book-section-card{border-top:1px solid var(--line)}.book-section-card:last-child{border-bottom:1px solid var(--line)}.book-section-card>button{text-align:left;cursor:pointer;background:0 0;border:0;grid-template-columns:55px 1fr 25px;gap:12px;width:100%;padding:23px 0;display:grid}.book-section-card>button>span{color:var(--blue);font:700 10px/2 var(--font-geist-mono),monospace}.book-section-card h3{letter-spacing:-.02em;margin:0;font-size:19px}.book-section-card button p{color:var(--muted);margin:7px 0 0;font-size:13px;line-height:1.6}.book-section-card button i{font-size:22px;font-style:normal}.book-section-body{background:#f7faff;border:1px solid #d9e5f8;border-radius:24px;margin:0 0 32px 67px;padding:30px}.book-section-body small,.chapter-reference-grid small{color:var(--blue);letter-spacing:.12em;margin-bottom:10px;font-size:8px;font-weight:600;display:block}.book-section-body ul{margin:0;padding-left:18px}.book-section-body li{color:#34445a;margin:10px 0;font-size:14px;line-height:1.75}.book-understanding-intro{background:#fff;border-radius:18px;padding:24px;box-shadow:0 1px #00000009}.book-understanding-intro h4{color:#172d52;letter-spacing:-.02em;margin:0;font-size:clamp(18px,2vw,24px);line-height:1.4}.book-understanding-intro p{color:var(--muted);margin:14px 0 0;font-size:13px;line-height:1.75}.book-explanation-grid{grid-template-columns:1.2fr .8fr;gap:12px;margin-top:12px;display:grid}.book-explanation-grid>section{background:#ffffffc2;border-radius:18px;padding:22px}.book-explanation-grid p{color:#34445a;margin:0;font-size:14px;line-height:1.75}.book-reading-route{background:#e9f2ff;border-radius:18px;margin-top:12px;padding:22px}.book-reading-route ol{grid-template-columns:1fr 1fr;column-gap:35px;margin:0;padding-left:22px;display:grid}.book-reading-route li{padding-left:4px}.book-formula,.book-example,.book-self-check{background:#fff;border-radius:18px;margin-top:12px;padding:22px}.book-formula code{color:#203e77;white-space:normal;font-size:13px;line-height:1.65;display:block}.book-formula p,.book-example p,.book-self-check p{color:var(--muted);margin:11px 0 0;font-size:13px;line-height:1.75}.book-example.generated{background:#ffffffa6;border:1px dashed #bed2ef}.book-self-check{color:#fff;background:#1d1d1f}.book-self-check small{color:#8bb8ff}.book-self-check p{color:#d1d1d6}.chapter-reference-grid{grid-template-columns:1fr 1fr;gap:12px;margin-top:70px;display:grid}.chapter-reference-grid>div{border:1px solid var(--line);background:#fff;border-radius:23px;padding:26px}.chapter-reference-grid h3{letter-spacing:-.025em;margin:0 0 18px;font-size:20px}.chapter-reference-grid ul{margin:0;padding-left:18px}.chapter-reference-grid li,.chapter-reference-grid p{color:var(--muted);margin:8px 0;font-size:12px;line-height:1.55}.chapter-bridge{color:#fff;background:#111115;border-radius:23px;margin-top:12px;padding:28px}.chapter-bridge p{color:#d1d1d6;margin:12px 0 0;font-size:15px;line-height:1.65}.formula-grid{grid-template-columns:repeat(4,1fr);gap:10px;margin-top:80px;display:grid}.formula-grid article{border:1px solid var(--line);background:#fff;border-radius:23px;min-height:265px;padding:23px}.formula-grid article>span{color:var(--blue);font:700 9px var(--font-geist-mono),monospace}.formula-grid h2{letter-spacing:-.03em;margin:30px 0 8px;font-size:21px}.formula-grid p{min-height:36px;color:var(--muted);font-size:11px;line-height:1.5}.formula-grid article div{gap:7px;margin-top:20px;display:grid}.formula-grid code{color:#273a64;background:var(--blue-soft);white-space:normal;border-radius:8px;padding:8px;font-size:9px}.test-picker h2,.r-cheatsheet h2,.source-note h2{letter-spacing:-.045em;margin:0;font-size:clamp(30px,3.6vw,48px);line-height:1.12}.test-picker,.r-cheatsheet{margin-top:100px}.test-picker>div{grid-template-columns:repeat(3,1fr);gap:12px;margin-top:30px;display:grid}.test-picker article{color:#fff;background:#111115;border-radius:22px;padding:28px}.test-picker small{color:#8bb8ff;letter-spacing:.12em;font-size:8px}.test-picker p{color:#b7b7bf;margin:17px 0 0;font-size:12px;line-height:1.6}.test-picker b{color:#fff}.r-cheatsheet>div{grid-template-columns:repeat(3,1fr);gap:10px;margin-top:30px;display:grid}.r-cheatsheet pre{color:#cdd8ea;background:#101015;border-radius:20px;margin:0;padding:23px;font-size:10px;line-height:1.65;overflow:auto}.assessment-strip{border:1px solid var(--line);background:var(--line);border-radius:23px;grid-template-columns:repeat(3,1fr);gap:1px;margin:80px 0 30px;display:grid;overflow:hidden}.assessment-strip div{background:#fff;min-height:110px;padding:20px}.assessment-strip small,.assessment-strip strong{display:block}.assessment-strip small{color:var(--muted);text-transform:uppercase;letter-spacing:.1em;font-size:8px}.assessment-strip strong{letter-spacing:-.025em;margin-top:19px;font-size:18px}.coverage-list{border-top:1px solid var(--line)}.coverage-list article{border-bottom:1px solid var(--line);grid-template-columns:72px 1fr;gap:18px;padding:23px 0;display:grid}.coverage-list article>span{border-radius:999px;align-self:start;width:max-content;padding:5px 7px;font-size:9px;font-weight:600}.coverage-list .verified{color:var(--green);background:#e2f4ea}.coverage-list .limited{color:var(--orange);background:#fff0d9}.coverage-list h2{margin:0;font-size:20px}.coverage-list p{color:var(--muted);margin:7px 0 0;font-size:13px;line-height:1.6}.source-note{background:#fff;border-radius:22px;max-width:760px;margin-top:50px;padding:30px}.source-note h2{font-size:26px}.source-note p{color:var(--muted);margin:17px 0 0;line-height:1.7}footer{border-top:1px solid var(--line);color:var(--muted);justify-content:space-between;gap:24px;padding:28px 5vw;font-size:10px;display:flex}footer b{color:var(--ink)}footer p{text-align:right;margin:0}@media (max-width:1100px){.topbar{grid-template-columns:1fr auto}.progress-pill{display:none}.book-shell{grid-template-columns:235px minmax(0,1fr);gap:30px}.formula-grid{grid-template-columns:repeat(2,1fr)}}@media (max-width:820px){.topbar{height:60px;padding:0 17px}.brand b{font-size:11px}.brand small{display:none}.topbar nav{z-index:90;border:1px solid var(--line);background:#fffffff0;border-radius:999px;padding:4px;position:fixed;bottom:10px;left:10px;right:10px;overflow-x:auto;transform:none;box-shadow:0 14px 45px #00000029}.topbar nav button{white-space:nowrap;flex:none;padding:9px 10px;font-size:10px}.hero{min-height:680px;padding:100px 22px 50px}.hero h1{font-size:39px}.page-shell>h1{font-size:44px}.hero-copy,.page-intro{font-size:14px}.hero-stats{grid-template-columns:1fr 1fr}.hero-stats div{border-bottom:1px solid var(--line);padding:18px 12px}.north-star{grid-template-columns:1fr;padding:80px 22px}.reader-shell{padding:70px 18px 110px;display:block}.module-rail{display:none}.week-switcher{margin-bottom:30px;padding-left:12px}.week-switcher>span{display:none}.week-switcher>div{width:100%}.module-heading{display:block}.module-heading h2{font-size:40px}.done-button{margin-top:18px}.simple-card{padding:24px}.textbook-note div{display:block}.textbook-note b{margin-top:7px;display:block}.concept-head{grid-template-columns:38px minmax(0,1fr) 34px;gap:12px;padding:22px 18px}.concept-head h3{font-size:19px}.concept-head i{width:32px;height:32px}.concept-body{margin:0 8px 8px;padding:24px 20px}.deep-two-up{grid-template-columns:1fr}.deep-two-up>div+div{border-top:1px solid #e8e8ed;border-left:0}.two-up,.test-picker>div,.r-cheatsheet>div{grid-template-columns:1fr}.page-shell{padding:90px 18px 110px}.book-stats{grid-template-columns:1fr 1fr}.book-controls{display:block}.book-controls>div{flex-wrap:nowrap;justify-content:flex-start;margin-top:18px;overflow-x:auto}.book-controls button{white-space:nowrap}.book-shell{display:block}.book-rail{gap:6px;max-height:none;margin-bottom:28px;display:flex;position:static;overflow-x:auto}.book-rail>div,.book-rail>p{display:none}.book-rail>button{min-width:170px}.book-reader>header{padding:27px}.book-section-body{margin-left:0}.book-explanation-grid,.book-reading-route ol,.chapter-reference-grid,.formula-grid{grid-template-columns:1fr}.assessment-strip{grid-template-columns:1fr 1fr}footer{padding-bottom:80px;display:block}footer p{text-align:left;margin-top:8px}}@media (max-width:480px){.brand-mark{width:34px;height:34px}.topbar nav button{padding:8px 7px;font-size:9px}.hero h1{font-size:34px}.page-shell>h1{font-size:37px}.hero-stats strong{font-size:20px}.section-head{display:block}.section-head>span{margin-top:8px;display:block}.concept-card{border-radius:22px}.deep-label{display:block}.deep-label b{margin-top:8px;display:block}}@media (prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;transition:none!important}}@property --tw-ordinal{syntax:"*";inherits:false}@property --tw-slashed-zero{syntax:"*";inherits:false}@property --tw-numeric-figure{syntax:"*";inherits:false}@property --tw-numeric-spacing{syntax:"*";inherits:false}@property --tw-numeric-fraction{syntax:"*";inherits:false}