:root{--paper:#ecede8;--panel:#f6f6f2;--ink:#22252a;--ink-2:#3b3f45;--muted:#5e6268;--rule-light:#c7c9c2;--leader:#9a9d96;--green:#2f6b4f;--green-light:#6e9c84;--bar-track:#e1e3dc;--green-wash:#dce8e0;--white:#fff;--font-serif:"Young Serif", Georgia, serif;--font-sans:"Public Sans", system-ui, -apple-system, "Segoe UI", Arial, sans-serif;--radius:4px;--max-width:1180px;--gutter:16px;--touch:44px;--bar-ms:.12s}@media (width>=800px){:root{--gutter:32px}}*,:before,:after{box-sizing:border-box}html{-webkit-text-size-adjust:100%}body{background:var(--paper);color:var(--ink);font-family:var(--font-sans);margin:0;font-size:17px;line-height:1.6}h1,h2,h3{font-family:var(--font-serif);color:var(--ink);margin:0;font-weight:400;line-height:1.1}p{margin:0}a{color:var(--green);text-underline-offset:3px}a:hover{color:var(--ink)}:focus-visible{outline:2px solid var(--green);outline-offset:3px}[tabindex="-1"]:focus{outline:none}.skip-link{background:var(--ink);color:var(--white);border-radius:var(--radius);z-index:10;padding:10px 14px;position:absolute;top:-60px;left:8px}.skip-link:focus{color:var(--white);top:8px}.container{max-width:var(--max-width);padding-left:var(--gutter);padding-right:var(--gutter);margin:0 auto}.muted{color:var(--muted)}.spacer{flex-grow:1}[hidden]{display:none!important}.sr-only{clip:rect(0, 0, 0, 0);white-space:nowrap;border:0;width:1px;height:1px;margin:-1px;padding:0;position:absolute;overflow:hidden}.btn{min-height:var(--touch);border:1px solid var(--ink);border-radius:var(--radius);background:var(--panel);color:var(--ink);font:700 16px/1.2 var(--font-sans);cursor:pointer;justify-content:center;align-items:center;padding:12px 22px;text-decoration:none;display:inline-flex}.btn:hover{color:var(--ink)}.btn-primary{background:var(--green);border-color:var(--green);color:var(--white)}.btn-primary:hover{color:var(--white);background:#275c43}.btn-dark{background:var(--ink);border-color:var(--ink);color:var(--white)}.btn-dark:hover{color:var(--white);background:#000}.btn:disabled{opacity:.55;cursor:not-allowed}.btn-lg{padding:16px 24px;font-size:17px}.btn-block{width:100%;padding:17px;font-size:17px}.link-button{min-height:var(--touch);color:var(--green);font:inherit;text-underline-offset:3px;cursor:pointer;background:0 0;border:0;padding:0;text-decoration:underline}.site-header{padding-top:24px}.masthead{border-bottom:1px solid var(--ink);flex-wrap:wrap;justify-content:space-between;align-items:center;gap:8px 16px;padding-bottom:10px;display:flex}.wordmark{font-family:var(--font-serif);color:var(--ink);min-height:var(--touch);align-items:center;font-size:24px;text-decoration:none;display:inline-flex}.site-nav{flex-wrap:wrap;gap:0 24px;font-size:16px;display:flex}.site-nav a{min-height:var(--touch);color:var(--ink);align-items:center;text-decoration:none;display:inline-flex}.site-nav a[aria-current=page]{text-decoration:underline}.site-nav .nav-cta{color:var(--green);font-weight:700;text-decoration:underline}.site-footer{padding-bottom:40px}.footer-inner{border-top:1px solid var(--ink);color:var(--ink-2);flex-wrap:wrap;justify-content:space-between;align-items:center;gap:8px 16px;padding-top:12px;font-size:15px;display:flex}.footer-nav{gap:24px;display:flex}.footer-nav a{color:var(--ink-2);min-height:var(--touch);align-items:center;display:inline-flex}.section{grid-template-columns:minmax(0,1fr);gap:20px 48px;padding-top:72px;padding-bottom:72px;display:grid}@media (width>=880px){.section{grid-template-columns:minmax(0,1fr) minmax(0,2fr);padding-top:88px;padding-bottom:88px}}.section-intro{flex-direction:column;gap:14px;display:flex}.section-intro h2{font-size:clamp(30px,4vw,38px)}.section-intro p{color:var(--ink-2);max-width:340px;line-height:1.65}.band{background:var(--panel);border-top:1px solid var(--ink);border-bottom:1px solid var(--ink)}.band+.band{border-top:0}.hero{grid-template-columns:minmax(0,1fr);gap:40px 56px;padding-top:48px;padding-bottom:56px;display:grid}@media (width>=980px){.hero{grid-template-columns:minmax(0,.85fr) minmax(0,1.15fr);padding-top:64px;padding-bottom:72px}}.hero-copy{flex-direction:column;gap:24px;padding-top:8px;display:flex}.hero h1{letter-spacing:-.5px;text-wrap:balance;font-size:clamp(38px,5.2vw,64px);line-height:1.04}.lede{color:var(--ink-2);max-width:440px;font-size:19px;line-height:1.65}.actions{flex-wrap:wrap;align-items:center;gap:12px 24px;display:flex}.text-link{color:var(--ink);min-height:var(--touch);align-items:center;font-weight:500;display:inline-flex}.temp-section{padding-bottom:88px}.figure{background:var(--panel);border:1px solid var(--ink);flex-direction:column;gap:14px;min-width:0;margin:0;padding:20px;display:flex}@media (width>=600px){.figure{padding:26px 30px 28px}}.figure-caption{color:var(--ink-2);flex-wrap:wrap;justify-content:space-between;gap:4px 12px;font-size:15px;display:flex}.fig-label{font-family:var(--font-serif);color:var(--ink);font-size:16px}.figure-note{color:var(--ink-2);font-size:16px;line-height:1.6}.fig-guess .figure-note{min-height:52px}.branch{width:100%;height:auto;display:block}.branch-prompt,.branch-word{font-family:var(--font-serif);fill:var(--ink)}.branch-word{font-size:25px}.branch-pct{font-family:var(--font-sans);fill:var(--ink-2);font-size:17px}.branch-line{fill:none;stroke:var(--leader);stroke-linecap:round;transition:stroke-width .4s,stroke .4s}.branch-line.is-revealed{stroke:var(--green)}.guesses{border-top:1px solid var(--rule-light);flex-wrap:wrap;align-items:center;gap:10px;padding-top:16px;display:flex}.guesses-label{margin-right:4px;font-size:16px;font-weight:700}.chip{min-height:var(--touch);border:1px solid var(--ink);border-radius:var(--radius);background:var(--white);color:var(--ink);font:16px var(--font-sans);cursor:pointer;padding:10px 16px}.chip[aria-pressed=true]{background:var(--ink);color:var(--white)}.fig-temp-grid{grid-template-columns:minmax(0,1fr);gap:32px 48px;display:grid}@media (width>=800px){.fig-temp-grid{grid-template-columns:minmax(0,1fr) minmax(0,1fr)}}.fig-temp-controls{flex-direction:column;gap:18px;display:flex}.fig-temp-bars{flex-direction:column;justify-content:center;gap:14px;display:flex}.story-block{border-top:1px solid var(--rule-light);flex-direction:column;gap:6px;padding-top:16px;display:flex}.story-label{color:var(--ink-2);font-size:14px}.story{font-family:var(--font-serif);min-height:68px;font-size:25px;line-height:1.35}.story--sm{min-height:52px;font-size:20px;line-height:1.3}.slider{flex-direction:column;display:flex}.slider-label{justify-content:space-between;align-items:baseline;font-size:16px;font-weight:700;display:flex}.slider-value{font-family:var(--font-serif);font-size:26px;font-weight:400}.slider input[type=range]{width:100%;height:var(--touch);accent-color:var(--green);cursor:pointer;margin:0}.slider-ends{color:var(--ink-2);justify-content:space-between;margin-top:-6px;font-size:14px;display:flex}.odds{flex-direction:column;gap:14px;margin:0;padding:0;list-style:none;display:flex}.odds-row{flex-direction:column;gap:6px;display:flex}.odds-head{justify-content:space-between;align-items:baseline;display:flex}.odds-word{font-family:var(--font-serif);font-size:21px}.odds-pct{font-variant-numeric:tabular-nums;font-size:16px;font-weight:700}.odds-track{background:var(--bar-track);height:14px;display:block}.odds-fill{background:var(--green);height:100%;transition:width var(--bar-ms) linear;display:block}.odds-fill--light{background:var(--green-light)}.odds--compact{gap:8px}.odds--compact .odds-row{flex-direction:row;align-items:center;gap:10px}.odds--compact .odds-head{display:contents}.odds--compact .odds-word{flex:0 0 56px;order:0;font-size:17px}.odds--compact .odds-track{flex-grow:1;order:1;height:10px}.odds--compact .odds-pct{text-align:right;flex:0 0 40px;order:2;font-size:14px}.steps{grid-template-columns:repeat(auto-fit,minmax(min(200px,100%),1fr));gap:32px;margin:0;padding:0;list-style:none;display:grid}.steps li{border-top:3px solid var(--green);flex-direction:column;gap:10px;padding-top:18px;display:flex}.steps h3{font-size:22px}.steps p{color:var(--ink-2);font-size:16px;line-height:1.6}.contents{flex-direction:column;gap:40px;display:flex}.contents-part-head{border-bottom:1px solid var(--ink);justify-content:space-between;align-items:baseline;gap:12px;margin-bottom:6px;padding-bottom:10px;display:flex}.contents-part-head h3{font-size:26px}.contents-rows{margin:0;padding:0;list-style:none}.contents-row{align-items:baseline;gap:14px;padding:8px 0;font-size:17px;display:flex}.contents-num{min-width:26px;color:var(--muted);font-variant-numeric:tabular-nums}.contents-title{flex-wrap:wrap;align-items:baseline;gap:4px 10px;display:inline-flex}a.contents-title{color:var(--ink);min-height:28px}a.contents-title:hover{color:var(--green)}.contents-leader{border-bottom:1px dotted var(--leader);flex-grow:1;min-width:16px}.contents-mins{color:var(--muted);white-space:nowrap}.soon{color:var(--muted);font-size:14px}.done-mark{color:var(--green);font-size:14px;font-weight:700}.signup{grid-template-columns:minmax(0,1fr);align-items:end;gap:24px 48px;padding-top:72px;padding-bottom:72px;display:grid}@media (width>=880px){.signup{grid-template-columns:minmax(0,1fr) minmax(0,1fr);padding-top:80px;padding-bottom:80px}}.signup-copy{flex-direction:column;gap:12px;display:flex}.signup-copy h2{font-size:clamp(28px,3.4vw,34px);line-height:1.15}.signup-copy p{color:var(--ink-2)}.signup-form{flex-direction:column;gap:8px;display:flex}.signup-form label{font-size:15px;font-weight:700}.signup-row{flex-wrap:wrap;gap:10px;display:flex}.signup-row input{min-width:0;min-height:var(--touch);border:1px solid var(--ink);border-radius:var(--radius);background:var(--white);color:var(--ink);font:17px var(--font-sans);flex:220px;padding:12px 16px}.signup-row input:disabled{background:var(--panel)}.signup-note{color:var(--muted);font-size:15px}.page-head{max-width:760px;padding-top:56px;padding-bottom:24px}.page-head h1{margin-bottom:16px;font-size:clamp(36px,5vw,52px);line-height:1.05}.page-head p{color:var(--ink-2);font-size:19px;line-height:1.6}.prose{max-width:680px;color:var(--ink-2);padding-bottom:80px}.prose h2{color:var(--ink);margin:40px 0 12px;font-size:26px}.prose p,.prose ul{margin:0 0 16px;line-height:1.7}.prose ul{padding-left:22px}.prose li{margin-bottom:8px}.prose strong{color:var(--ink)}.lesson-page main{min-height:100svh}.shell{max-width:560px;min-height:100svh;padding:18px var(--gutter) 28px;flex-direction:column;gap:22px;margin:0 auto;display:flex}.shell-bar{border-bottom:1px solid var(--ink);align-items:center;gap:14px;padding-bottom:14px;display:flex}.shell-close{width:var(--touch);height:var(--touch);border:1px solid var(--ink);border-radius:var(--radius);color:var(--ink);flex:none;justify-content:center;align-items:center;display:flex}.shell-close:hover{background:var(--panel);color:var(--ink)}.shell-status{flex-direction:column;flex-grow:1;gap:6px;display:flex}.shell-step{color:var(--ink-2);font-size:14px}.shell-track{background:var(--rule-light);height:3px}.shell-fill{background:var(--green);height:3px;transition:width .4s}.shell-xp{color:var(--green);font-variant-numeric:tabular-nums;font-size:15px;font-weight:700}.shell-body{flex-direction:column;flex-grow:1;gap:18px;display:flex}.step-kicker{color:var(--ink-2);font-size:15px}.lesson-h1{font-size:40px;line-height:1.05}.lesson-h2{font-size:30px;line-height:1.12}.lesson-h2--lg{font-size:36px;line-height:1.08}.lesson-lede{color:var(--ink-2);font-size:18px;line-height:1.6}.lesson-text{color:var(--ink-2);font-size:16px;line-height:1.6}.plan-box{border:1px solid var(--ink);background:var(--panel);flex-direction:column;gap:10px;padding:18px 20px;display:flex}.plan-box strong{font-size:15px}.plan-box ol{flex-direction:column;gap:8px;margin:0;padding-left:22px;line-height:1.5;display:flex}.prompt-line{font-size:32px;line-height:1.2}.blank{color:var(--muted)}.blank.is-filled{color:var(--green);border-bottom:2px solid var(--green)}.predict{border-top:1px solid var(--ink);flex-direction:column;display:flex}.predict-opt{width:100%;min-height:var(--touch);border:0;border-bottom:1px solid var(--rule-light);color:var(--ink);font:inherit;text-align:left;cursor:pointer;background:0 0;flex-direction:column;gap:8px;padding:14px 6px 12px;display:flex}.predict-opt:hover:not([aria-disabled=true]){background:var(--panel)}.predict-opt[aria-disabled=true]{cursor:default}.predict-opt[aria-pressed=true]{background:var(--panel)}.predict-row{justify-content:space-between;align-items:baseline;width:100%;display:flex}.predict-word{font-family:var(--font-serif);font-size:22px}.predict-yours{font-family:var(--font-sans);color:var(--ink-2);margin-left:10px;font-size:14px}.predict-pct{color:var(--ink-2);font-variant-numeric:tabular-nums;font-size:15px}.predict-linewrap{align-items:center;width:100%;height:14px;display:flex}.predict-line{background:var(--rule-light);border-radius:99px;transition:width .5s,height .5s,background-color .3s;display:block}.predict-line.is-revealed{background:var(--green)}.feedback{color:var(--ink-2);font-size:16px;line-height:1.6}.feedback.is-answered{color:var(--ink)}.story-box{border:1px solid var(--ink);background:var(--panel);flex-direction:column;gap:6px;margin:0;padding:14px 16px;display:flex}.story-box figcaption{color:var(--ink-2);font-size:14px}.completion{flex-direction:column;flex-grow:1;gap:20px;display:flex}.stats{border-top:1px solid var(--ink);margin:0}.stat-row{border-bottom:1px solid var(--rule-light);justify-content:space-between;padding:12px 0;font-size:17px;display:flex}.stat-row:last-child{border-bottom-color:var(--ink)}.stat-row dt{margin:0}.stat-row dd{margin:0;font-weight:700}.takeaway{border-top:3px solid var(--green);flex-direction:column;gap:8px;padding-top:14px;display:flex}.takeaway-title{font-size:21px}.takeaway p{color:var(--ink-2);font-size:17px;line-height:1.6}.completion-actions{flex-direction:column;gap:10px;display:flex}.next-soon{color:var(--ink-2);font-size:16px}.completion-links{flex-wrap:wrap;justify-content:space-between;align-items:center;gap:8px 20px;display:flex}.completion-links a{min-height:var(--touch);align-items:center;display:inline-flex}.part-done{border:1px solid var(--ink);background:var(--green-wash);padding:12px 14px;font-size:16px;line-height:1.55}.fine-print{color:var(--muted);font-size:14px}.figure.figure--tight{gap:10px;padding:14px 16px}.choice{flex-direction:column;gap:14px;display:flex}.choice-list{border-top:1px solid var(--ink);flex-direction:column;display:flex}.choice-opt{width:100%;min-height:var(--touch);border:0;border-bottom:1px solid var(--rule-light);color:var(--ink);font:17px/1.45 var(--font-sans);text-align:left;cursor:pointer;background:0 0;justify-content:space-between;align-items:baseline;gap:12px;padding:14px 6px;display:flex}.choice-opt:hover:not([aria-disabled=true]){background:var(--panel)}.choice-opt[aria-disabled=true]{cursor:default}.choice-opt.is-correct{background:var(--green-wash);font-weight:700}.choice-opt.is-wrong{background:var(--panel)}.choice-opt.is-dim{color:var(--muted)}.choice-tag{color:var(--ink-2);flex:none;font-size:14px;font-weight:700}.choice-opt.is-correct .choice-tag{color:var(--green)}.label-strip{grid-template-columns:repeat(10,minmax(0,1fr));gap:6px;display:grid}.label-cell{background:var(--green);border:1px solid var(--green);height:22px;transition:background-color .15s;display:inline-block}.label-cell.is-wrong{background:var(--white);border:1px dashed var(--ink)}.strip-legend{color:var(--ink-2);flex-wrap:wrap;gap:6px 18px;font-size:14px;display:flex}.strip-legend .label-cell{vertical-align:-2px;width:14px;height:14px;margin-right:4px}.meter{flex-direction:column;gap:6px;display:flex}.meter-head{justify-content:space-between;align-items:baseline;font-weight:700;display:flex}.meter-value{font-family:var(--font-serif);font-size:30px;font-weight:400}.inbox{margin:0;padding:0;list-style:none}.inbox-row{border-bottom:1px solid var(--rule-light);justify-content:space-between;align-items:baseline;gap:12px;padding:8px 0;font-size:15px;display:flex}.inbox-row:last-child{border-bottom:0}.inbox-verdict{color:var(--ink-2);flex:none;align-items:baseline;gap:8px;display:flex}.inbox-row.is-wrong .inbox-subject{font-weight:700}.inbox-flag{color:var(--ink);background:var(--bar-track);border-radius:2px;padding:0 6px;font-size:13px}.toggles{flex-wrap:wrap;gap:8px;display:flex}.prompt-box{font-size:16px;line-height:1.5}.prompt-box--small{color:var(--ink-2);font-size:14px}.email{background:var(--white);border:1px solid var(--rule-light);white-space:pre-line;flex-direction:column;gap:8px;padding:12px 14px;font-size:16px;line-height:1.55;display:flex}.email-subhead{margin-top:4px;font-weight:700}.blank-mark{background:var(--bar-track);color:var(--ink);border-bottom:1px dashed var(--ink-2);border-radius:2px;padding:0 3px}.spot{flex-direction:column;gap:12px;display:flex}.spot-card{border:1px solid var(--ink);border-radius:var(--radius);background:var(--white);width:100%;color:var(--ink);font:16px/1.55 var(--font-sans);text-align:left;cursor:pointer;flex-direction:column;gap:8px;padding:14px 16px;display:flex}.spot-card:hover:not([aria-disabled=true]){background:var(--panel)}.spot-card[aria-disabled=true]{cursor:default}.spot-card-head{justify-content:space-between;align-items:baseline;gap:8px;display:flex}.spot-card-name{font-family:var(--font-serif);font-size:18px}.spot-card-tag{color:var(--ink-2);font-size:14px;font-weight:700}.spot-card.is-ai{outline:2px solid var(--green);outline-offset:-2px}.spot-card.is-ai .spot-card-tag{color:var(--green)}.spot-card.is-human{background:var(--panel)}.tells ul{color:var(--ink-2);margin:8px 0 0;padding-left:20px;line-height:1.55}.tells li{margin-bottom:4px}.source{flex-direction:column;gap:4px;margin:0;padding:0;font-size:15px;list-style:none;display:flex}.source-line{padding:4px 8px;transition:background-color .2s}.source-line.is-used{background:var(--green-wash)}.claims{margin:0;padding-left:22px}.claim{border-bottom:1px solid var(--rule-light);padding:10px 0}.claim:last-child{border-bottom:0}.claim-text{font-size:16px;line-height:1.5}.claim.is-made .claim-text{text-decoration:line-through;text-decoration-color:var(--ink-2)}.claim-actions{flex-wrap:wrap;gap:8px;margin-top:8px;display:flex}.claim-verdict{color:var(--ink-2);margin-top:6px;font-size:15px}.claim.is-source .claim-verdict strong{color:var(--green)}.sort{border-top:1px solid var(--ink);margin:0;padding:0;list-style:none}.sort-row{border-bottom:1px solid var(--rule-light);padding:12px 0}.sort-task{font-size:17px}.sort-verdict{color:var(--ink-2);margin-top:6px;font-size:15px}.sort-row.is-right .sort-verdict strong{color:var(--green)}.notes{color:var(--ink-2);font-size:15px;font-style:italic;line-height:1.55}.prompt-box--pre{white-space:pre-line}.cite{color:var(--green);font-size:14px;font-weight:700}.source-toggle{min-height:36px;font-size:15px}.source-toggle:disabled{color:var(--ink-2);cursor:default;text-decoration:none}.source-quote{background:var(--white);border:1px solid var(--rule-light);margin-top:4px;padding:8px 12px;font-size:15px;line-height:1.5}.source-title{color:var(--ink-2);margin-bottom:2px;font-size:13px;font-weight:700;display:block}.chip-row{flex-direction:column;gap:6px;display:flex}.chip-row-label{color:var(--ink-2);font-size:14px;font-weight:700}.sketch-frame{border:1px solid var(--ink);background:var(--white);aspect-ratio:4/3;overflow:hidden}.sketch-frame svg,.sketch-frame img{object-fit:cover;width:100%;height:100%;display:block}.sketch path,.sketch rect,.sketch circle,.sketch polygon{transition:fill .25s}.lesson-h3{margin-top:12px;font-size:22px}.kit{flex-direction:column;margin:0;padding:0;list-style:none;display:flex}.kit-item{border-bottom:1px solid var(--rule-light);flex-direction:column;gap:6px;padding:12px 0;display:flex}.kit-item:first-child{padding-top:0}.kit-item:last-child{border-bottom:0;padding-bottom:0}.kit-name{font-size:19px}.kit-for{color:var(--green);font-size:14px;font-weight:700}.kit-tip{color:var(--ink-2);font-size:15px;line-height:1.55}.progress-summary{background:var(--panel);border:1px solid var(--ink);margin:0;padding:12px 14px;font-size:16px}.part-page{grid-template-columns:minmax(0,1fr);gap:40px 56px;padding-top:48px;padding-bottom:80px;display:grid}@media (width>=900px){.part-page{grid-template-columns:minmax(0,1.2fr) minmax(0,1fr);align-items:start}}.share-card{border:1px solid var(--ink);background:var(--panel);flex-direction:column;gap:14px;padding:24px;display:flex}@media (width>=600px){.share-card{padding:32px}}.share-card-head{border-bottom:1px solid var(--ink);flex-wrap:wrap;justify-content:space-between;align-items:baseline;gap:8px;padding-bottom:12px;display:flex}.share-card-brand{font-family:var(--font-serif);font-size:20px}.share-card-kicker{color:var(--green);font-weight:700}.share-card-title{font-size:clamp(32px,4.5vw,48px);line-height:1.05}.share-card-list{columns:2 200px;color:var(--ink-2);margin:0;padding-left:22px}.share-card-stats{font-family:var(--font-serif);font-size:24px}.part-panel{flex-direction:column;gap:14px;display:flex}.part-panel h2{font-size:30px}.part-panel p{color:var(--ink-2)}.share-status{min-height:1.6em}.auth-page{max-width:720px;margin-left:0;padding-bottom:80px}.auth-page .page-head{padding-bottom:28px}.auth-form{flex-direction:column;gap:8px;max-width:560px;display:flex}.auth-form label{font-size:15px;font-weight:700}.auth-status{min-height:1.6em;color:var(--ink-2)}.auth-sent{flex-direction:column;gap:12px;max-width:560px;display:flex}.auth-sent h2,.auth-h2{font-size:30px}.auth-h2{margin-bottom:14px}.auth-note{max-width:560px;margin-top:32px;font-size:15px}.auth-page .stats{max-width:560px}.auth-page .actions{margin-top:20px}@media (prefers-reduced-motion:reduce){*,:before,:after{scroll-behavior:auto!important;transition-duration:.01ms!important;animation-duration:.01ms!important}}