:root{--ink:#183532;--muted:#566b67;--teal:#16786b;--deep:#115e54;--paper:#f5f4ef;--line:#d5dfd8;--soft:#e8f2ec;--warm:#fcf0d9;--white:#fff;--radius:18px;font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;color:var(--ink);background:var(--paper)}
 [hidden]{display:none!important}.app-layout{display:grid;grid-template-columns:210px minmax(0,1fr);max-width:1450px;margin:auto}.app-layout main{width:100%;min-width:0}#units{padding:30px 15px;border-right:1px solid var(--line)}#units h2{font-size:16px}#units button{text-align:left;width:100%}#unit-lessons{display:flex;gap:8px;overflow-x:auto;padding-bottom:12px;margin-bottom:22px}#unit-lessons button{flex:0 0 180px;text-align:left;font-size:13px}#unit-lessons small{display:block;font-weight:400;margin-top:8px}#unit-lessons [aria-current]{border-color:var(--teal);background:var(--soft)}#stages{flex-wrap:wrap}#stages li{padding:0;min-width:100px}#stages button{width:100%;font-size:12px;padding:8px;display:flex;gap:6px;align-items:center}#help{padding:18px;background:var(--soft);margin-bottom:20px;border-radius:12px}.site-header .actions{margin:0}.report-summary{overflow-wrap:anywhere;font-size:14px;line-height:1.6}.report-question{break-inside:avoid;margin-top:24px;border-top:1px solid var(--line);padding-top:12px}.report-question .diagram-wrap{max-width:450px}.report-question p{overflow-wrap:anywhere}input[type=text],#report-identifier{padding:9px;border:1px solid var(--line);border-radius:8px;max-width:100%}
@media(max-width:850px){.app-layout{grid-template-columns:1fr}#units{border-right:0;padding:15px 20px;border-bottom:1px solid var(--line)}#units h2{margin:0 0 8px}#units button{width:auto}.site-header{flex-wrap:wrap}#unit-lessons button{flex-basis:160px}}
@media print{@page{margin:15mm}body{background:white;color:#111}.site-header,#units,main>nav,#help,#overview,#student-lesson,footer,.report-controls{display:none!important}.app-layout,main{display:block!important;width:100%;max-width:none;padding:0;margin:0}#report-view{display:block!important;border:0;padding:0}#print-report-content{display:block}.report-question svg{max-height:none;width:100%}.diagram-wrap{background:white;padding:0}.triangle-edge{stroke:#444}.triangle-edge.selected{stroke:#111;stroke-width:6}.h-label,.vertex-label{fill:#111}.report-question{break-inside:avoid;page-break-inside:avoid}h1,h2,h3{break-after:avoid}.report-summary{font-size:11pt}}
*{box-sizing:border-box}body{margin:0}button,input,textarea,select{font:inherit}button{cursor:pointer;border:1px solid transparent;border-radius:10px;padding:12px 19px;background:var(--teal);color:white;font-weight:650;min-height:44px}button:hover{background:var(--deep)}button:disabled{opacity:.45;cursor:default}button.quiet{background:white;border-color:var(--line);color:var(--ink)}button.quiet:hover{background:var(--soft)}:focus-visible{outline:3px solid #b16d21;outline-offset:4px}p{line-height:1.65}h1,h2,h3{letter-spacing:-.025em}h1{font-size:clamp(30px,4vw,44px);margin:8px 0}h2{font-size:28px;margin:8px 0 16px}h3{font-size:19px}a{color:var(--deep)}.site-header{padding:20px max(24px,calc((100vw - 1120px)/2));background:white;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;gap:16px}.brand{display:flex;gap:12px;align-items:center}.brand-mark{font-size:38px;color:var(--teal)}.brand strong,.brand 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span{font-weight:400;color:var(--muted);margin-left:8px}#preferences{display:flex;flex-wrap:wrap;gap:8px 20px}#preferences label{display:flex;gap:7px;align-items:center;font-size:13px;min-height:32px}input[type=checkbox]{accent-color:var(--teal);width:17px;height:17px}nav ol{display:flex;list-style:none;padding:0;margin:0 0 22px;gap:8px}nav li{flex:1;font-size:13px;color:var(--muted);padding:11px 5px;border-bottom:3px solid var(--line);display:flex;align-items:center;gap:8px}nav .active{color:var(--deep);border-color:var(--teal);font-weight:700}nav .done{border-color:#84b9a5}nav .letter{border:1px solid var(--line);width:26px;height:26px;display:inline-grid;place-items:center;border-radius:50%;font-size:12px}.active .letter{color:white;background:var(--teal);border-color:var(--teal)}.lesson-surface{background:white;border:1px solid var(--line);border-radius:var(--radius);padding:30px;min-height:440px}.stage-kicker{font-size:12px;color:var(--teal);font-weight:750;letter-spacing:.08em}.intro-layout,.task-layout{display:grid;grid-template-columns:1fr 1fr;gap:30px;align-items:start}.intro-copy{max-width:620px}.criteria{padding-left:22px;line-height:1.8}.purpose{color:var(--muted)}.diagram-wrap{background:#f8faf7;border-radius:14px;padding:12px;position:relative}.diagram-wrap svg{width:100%;display:block;max-height:350px}.diagram-caption{text-align:center;font-size:12px;color:var(--muted);margin:0 0 8px}.triangle-edge{stroke:#68817a;stroke-width:3;fill:none;stroke-linecap:round}.triangle-edge.selected{stroke:var(--teal);stroke-width:6}.triangle-edge.model-highlight{stroke:var(--teal);stroke-width:6}.side-hit{stroke:none;fill:transparent;cursor:pointer;pointer-events:all}.side-hit:hover,.side-hit:focus{fill:#16786b22;outline:none}.vertex-hit{fill:transparent;cursor:pointer}.vertex-hit:hover,.vertex-hit:focus{fill:#16786b33;outline:none}.right-marker{stroke:#6c7771;stroke-width:2;fill:none}.right-marker.highlight{stroke:var(--teal);stroke-width:4}.vertex-label{font-size:15px;fill:var(--muted)}.h-label{font-size:20px;font-weight:700;fill:var(--deep)}.actions{display:flex;gap:10px;flex-wrap:wrap;margin-top:22px}.help-actions{display:flex;gap:8px;flex-wrap:wrap;margin-top:18px}.help-actions button{font-size:13px;padding:9px 13px}.feedback{border-left:3px solid var(--teal);padding:10px 14px;margin-top:18px;background:var(--soft);line-height:1.6;font-size:14px}.feedback.warning{border-color:#ac7b28;background:var(--warm)}.feedback p{margin:0}.answer-label{display:block;font-weight:650;font-size:14px;margin:18px 0 8px}textarea{width:100%;padding:12px;border:1px solid #adbfB6;border-radius:9px;min-height:95px;resize:vertical;color:var(--ink);background:white}.note-prompt{padding-top:16px;border-top:1px solid var(--line);margin-top:20px}.note-prompt ol{padding-left:23px;line-height:1.8}.small{font-size:13px;color:var(--muted)}.check-progress{display:flex;align-items:center;gap:12px;font-size:13px;color:var(--muted);margin-bottom:15px}.check-progress progress{accent-color:var(--teal);height:9px;width:120px}.review-list{padding-left:22px;line-height:1.9}.status{font-size:13px;color:var(--muted);margin-top:6px}.evidence-heading{display:flex;justify-content:space-between;gap:12px;align-items:center}#evidence{margin-top:25px;padding:22px;background:white;border:1px solid var(--line);border-radius:14px}.table-scroll{overflow-x:auto}table{border-collapse:collapse;width:100%;font-size:13px}th,td{text-align:left;border:1px solid var(--line);padding:10px;vertical-align:top}th{background:var(--soft)}.event-list{font-size:13px;line-height:1.7;padding-left:20px}.teacher-controls{margin-top:18px;padding-top:14px;border-top:1px solid var(--line)}footer{text-align:center;font-size:12px;color:var(--muted);margin:24px 0 5px}.selection-text{font-size:13px;font-weight:650;color:var(--deep);min-height:24px}.model-steps{padding-left:22px;line-height:1.8}.reflection-saved{color:var(--deep);font-size:13px}
@media(max-width:700px){main{padding:23px 15px}.site-header{padding:15px}.prototype{max-width:125px;text-align:right}.intro-layout,.task-layout{grid-template-columns:1fr;gap:18px}.lesson-surface{padding:22px 18px}nav li{font-size:11px;gap:4px;flex-direction:column}nav .letter{width:23px;height:23px}.profile-controls button{font-size:12px}.task-layout .diagram-wrap{order:0}.task-layout .task-copy{order:1}h2{font-size:24px}}
.chunk-label{font-size:13px;color:var(--muted);border-bottom:1px solid var(--line);padding-bottom:12px;margin-top:0}
.report-textbook img{display:block;width:100%;height:auto}
.textbook-layout{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:24px;align-items:start;margin-top:20px}
.book-question{border:1px solid var(--line);border-radius:12px;padding:18px;margin-bottom:18px;overflow-wrap:anywhere}
.book-question h3{margin-top:0}.book-answer{width:100%;min-width:0}.book-tick{display:flex;align-items:center;gap:8px;min-height:44px}
.book-question .actions,.book-question .help-actions{margin-top:14px}.book-question .help-actions button{flex:1 1 130px}
.textbook-resource{margin:0 0 15px}.textbook-resource img{width:100%;height:auto;display:block}.textbook-resource figcaption{font-size:13px;line-height:1.5;margin-top:10px}
.textbook-layout{grid-template-columns:1fr}.textbook-image-scroll{overflow-x:auto;border:1px solid var(--line);border-radius:10px;padding:8px}.textbook-image-scroll img{min-width:850px}.book-questions{display:grid;grid-template-columns:minmax(0,1fr);gap:18px}.book-questions .book-question{margin:0}
#textbook-dialog{max-width:95vw;width:1100px;max-height:92vh;border:1px solid var(--line);border-radius:12px;padding:20px}
#textbook-dialog::backdrop{background:#18353299}.image-scroll{overflow:auto;max-height:70vh}.image-scroll img{display:block;width:100%;min-width:750px;height:auto}
#stages li{flex:1 1 150px}#stages button{white-space:normal;text-align:left;min-height:58px}#stages .letter{flex-shrink:0}
@media(max-width:850px){.textbook-layout,.book-questions{grid-template-columns:1fr}}
@media print{dialog{display:none!important}.report-question .diagram-wrap{break-inside:avoid}.report-summary{overflow-wrap:anywhere}.report-question p{overflow-wrap:anywhere}}
.feedback.error{color:#8c2020;background:#fff1f0;border-color:#b32626}
.welcome-stages{display:grid;grid-template-columns:minmax(140px,230px) minmax(0,1fr);gap:12px 22px;line-height:1.6}.welcome-stages dt{font-weight:650}.welcome-stages dd{margin:0}.overview-learning{line-height:1.8;padding-left:22px}.lesson-outline{list-style:none;padding:0;display:grid;gap:16px}.lesson-outline li{border-top:1px solid var(--line);padding-top:12px}.lesson-outline h3{margin:0}.lesson-outline p{margin:8px 0}.settings-section{border-top:1px solid var(--line);margin-top:24px;padding-top:16px}.settings-section h2{font-size:22px}.settings-section p{max-width:75ch}.about-version{margin-top:24px;color:var(--muted);font-size:12px;line-height:1.6}.about-version summary{cursor:pointer;min-height:44px;padding:12px 0;font-weight:650}.about-version p{margin:8px 0}#home-toggle[aria-current="page"]{border-color:var(--teal);background:var(--soft)}
@media(max-width:700px){.welcome-stages{grid-template-columns:1fr;gap:6px}.welcome-stages dd{margin-bottom:12px}}
@media print{#welcome,#teacher-view{display:none!important}}
.feedback.neutral{color:var(--ink);background:#f0f3f2;border-color:#71847e}
.feedback.correct{color:var(--deep);background:var(--soft);border-color:var(--teal)}
.year-section{border-bottom:1px solid var(--line);padding:10px 0}.year-section summary{cursor:pointer;font-size:15px;font-weight:650;min-height:44px;padding:12px 0}.year-section .topic-list{display:grid;gap:10px;margin-bottom:12px}.topic-card{border:1px solid var(--line);border-radius:10px;padding:12px;background:white;line-height:1.5;overflow-wrap:anywhere}.topic-card .topic-number{display:block;font-size:11px;font-weight:650;color:var(--muted);margin-bottom:4px}.topic-card .topic-title{display:block;font-size:14px}.topic-card .topic-status{display:block;font-size:12px;color:var(--muted);margin-top:6px}#units .topic-card{width:100%;text-align:left}#units button.topic-card[aria-current]{border-color:var(--teal);background:var(--soft)}.stage-availability{display:block;font-size:11px;font-weight:400}.practice-finish{border-top:1px solid var(--line);padding-top:18px;margin-top:24px}
#chunks{display:grid;gap:10px;margin-bottom:20px}.chunk-navigation{border:1px solid var(--line);border-radius:10px;padding:12px}.chunk-navigation .actions{margin:8px 0 0}.theorem-diagram{margin:20px auto;max-width:560px}.theorem-diagram svg{display:block;width:100%;height:auto}.theorem-diagram text{font-size:18px;fill:var(--ink)}.theorem-diagram figcaption{font-size:13px;line-height:1.6}.side-square{stroke:#34645b;stroke-width:2}.square-0{fill:#e5f1fe}.square-2{fill:#fff0ce}.square-1{fill:#d6eee2}.equation{font-size:22px;font-weight:650;overflow-wrap:anywhere}.visible-steps li{padding:8px 0;line-height:1.7}.guided-question{border-top:1px solid var(--line);margin-top:22px;padding-top:16px}
dialog[id^="textbook-dialog"]{max-width:95vw;width:1100px;max-height:92vh;border:1px solid var(--line);border-radius:12px;padding:20px}dialog[id^="textbook-dialog"]::backdrop{background:#18353299}
@media print{#chunks{display:none!important}.theorem-diagram{break-inside:avoid}.report-textbook img{width:100%;height:auto;object-fit:contain}}
/* Compact lesson outline; keep teaching and textbook typography unchanged. */
#overview > h2:has(+ .lesson-outline){font-size:20px;margin:14px 0 8px}
#overview .lesson-outline{grid-template-columns:minmax(0,1fr);gap:6px;margin:0}
#overview .lesson-outline li{padding-top:6px;min-width:0}
#overview .lesson-outline h3{font-size:16px;line-height:1.25;margin:0}
#overview .lesson-outline p{font-size:14px;line-height:1.35;margin:3px 0 4px;overflow-wrap:anywhere}
#overview .lesson-outline .small{font-size:12px;line-height:1.3}
#overview .lesson-outline #begin{font-size:14px;padding:6px 12px;min-height:44px}
/* Only Part navigation uses columns; textbook response cards stay stacked. */
#chunks{grid-template-columns:repeat(3,minmax(0,1fr));align-items:stretch}
#chunks .chunk-navigation{display:flex;flex-direction:column;gap:8px;min-width:0}
#chunks .chunk-navigation strong{line-height:1.4;overflow-wrap:anywhere}
#chunks .chunk-navigation .actions{margin-top:auto;display:flex;flex-wrap:nowrap;gap:6px;padding-top:4px}
#chunks .chunk-navigation button{flex:1;min-width:0;padding:10px 8px;white-space:normal}
#chunks .chunk-navigation[aria-current="step"]{border:2px solid var(--teal);padding:11px;background:var(--soft)}
#chunks button[aria-current="step"]{border-color:var(--teal);font-weight:750}
@media(max-width:1000px){#chunks{grid-template-columns:minmax(0,1fr)}}