@import url('../../assets/css/tokens.css');
:root{--ink:#172f2c;--green:#174e43;--muted:#526862;--line:#d1ded6;--paper:#f4f5ef;--accent:#aeda7f}*{box-sizing:border-box}body{margin:0;color:var(--ink);background:var(--paper);font:18px/1.6 system-ui,'Microsoft YaHei',sans-serif}button,a,select{touch-action:manipulation}button{font:inherit;font-size:14px;cursor:pointer;border:1px solid var(--line);border-radius:8px;background:white;color:var(--ink);padding:10px 15px;min-height:44px}button:hover{border-color:var(--green);background:#ecf2e8}button:disabled{opacity:.4;cursor:default}button:focus-visible,a:focus-visible,select:focus-visible{outline:3px solid #bd7433;outline-offset:3px}a{color:var(--green)}[hidden]{display:none!important}.skip{position:absolute;left:0;top:-60px;background:white;z-index:10}.skip:focus{top:0}header{max-width:1500px;margin:auto;display:flex;align-items:center;gap:24px;padding:17px 4vw;border-bottom:1px solid var(--line)}.brand{font-weight:800;letter-spacing:2px;text-decoration:none}.brand span{font-size:13px;letter-spacing:0;border-left:1px solid var(--line);margin-left:10px;padding-left:12px}.book{font-size:13px;color:var(--muted)}.tools{margin-left:auto;display:flex;gap:6px}.tools button{font-size:12px;padding:7px 10px}main{max-width:1440px;padding:26px 4vw 12px;margin:auto;min-height:calc(100vh - 210px)}.eyebrow{display:flex;gap:15px;align-items:center;color:var(--muted);font-size:14px;letter-spacing:1px}.eyebrow b{background:var(--green);color:white;border-radius:4px;padding:3px 10px;font-weight:500}.heading{display:flex;align-items:baseline;gap:20px;margin-bottom:20px}h1{font-size:clamp(26px,3.3vw,48px);line-height:1.25;letter-spacing:-1px;margin:16px 0 8px;font-weight:750}.number{margin-left:auto;color:#91a297;font:300 56px/1 ui-monospace,monospace}.screen{display:grid;grid-template-columns:minmax(0,1fr);gap:16px}.visual{background:white;border:1px solid var(--line);border-radius:16px;padding:24px 30px;min-width:0;box-shadow:0 8px 24px #1c443208}h2{font-size:clamp(21px,2.2vw,30px);line-height:1.45;margin:0 0 18px}.formula{border-left:4px solid var(--green);background:#e7eee2;padding:17px 24px;border-radius:0 8px 8px 0;font-size:clamp(18px,1.9vw,27px);line-height:1.6;overflow-wrap:anywhere}.formula mark{background:#d3e8b4;color:inherit}.formula small{display:block;font-size:12px;letter-spacing:2px;color:var(--muted);margin-bottom:5px}.bitrow{display:flex;align-items:center;gap:20px;margin:16px 0;flex-wrap:wrap}.bitrow>span{font-size:16px;min-width:160px;color:var(--muted)}.bitgroups{display:flex;gap:13px;flex-wrap:wrap}.bitgroup{display:flex;gap:6px}.bit{display:flex;flex-direction:column;align-items:center;justify-content:center;min-width:43px;height:68px;border:1px solid var(--line);border-radius:7px;background:#f6f8f3;font:700 28px/1.2 ui-monospace,monospace}.bit small{font:10px/1.4 system-ui;color:var(--muted)}.bit.active{background:var(--green);color:white;border-color:var(--green)}.bit.active small{color:#d3e8d8}.bit.moving{animation:move-in .65s ease both;animation-delay:calc(var(--i)*40ms)}@keyframes move-in{from{transform:translateX(var(--offset));opacity:.25}to{transform:translateX(0);opacity:1}}.memory{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:8px;margin:15px 0}.memory-cell{border:1px solid var(--line);border-radius:8px;padding:9px;text-align:center;background:#f4f7ef}.memory-cell small{display:block;font:12px ui-monospace,monospace;color:var(--muted)}.memory-cell b{font:600 28px ui-monospace,monospace}.memory-cell.active{background:#deedc9;border-color:#789653;animation:fade-in .45s ease}.memory-cell.empty{background:repeating-linear-gradient(45deg,#fff,#fff 5px,#eff1eb 5px,#eff1eb 10px);color:#738374}.facts{display:flex;gap:12px;flex-wrap:wrap;margin:15px 0}.fact{flex:1;min-width:150px;padding:14px 18px;background:#f0f4ea;border-radius:9px}.fact small{display:block;color:var(--muted);font-size:13px}.fact b{font-size:24px}.conclusion{margin:18px 0 0;font-size:19px;color:#31574b;border-top:1px solid var(--line);padding-top:14px}.bullets{margin:10px 0;padding-left:1.3em;font-size:21px}.bullets li{margin:12px 0}.flow{display:flex;gap:16px;align-items:center;flex-wrap:wrap;margin:26px 0}.flow span{flex:1;border:1px solid var(--line);padding:22px;border-radius:10px;background:#f0f5ea;text-align:center;font-size:22px}.table-wrap{overflow:auto}table{border-collapse:collapse;width:100%;font-size:20px;margin:16px 0}td,th{padding:11px 15px;border-bottom:1px solid var(--line);text-align:left}th{background:#edf3e6;font-weight:600}.quiz-list{display:grid;gap:12px}.question{padding:18px 22px;border:1px solid var(--line);border-radius:10px;background:white}.question p{font-size:21px;margin:0 0 12px}.answer{border-left:3px solid #6a903f;padding:12px 18px;margin:14px 0;background:#edf4e2;font-size:20px}.controls{position:sticky;bottom:0;background:#f4f5eff5;backdrop-filter:blur(12px);border-top:1px solid var(--line);padding:14px 4vw;display:flex;justify-content:space-between;align-items:center;gap:15px;z-index:3}.nav{display:flex;gap:7px;flex-wrap:wrap}.primary{background:var(--green);color:white;border-color:var(--green);padding-inline:24px}.primary:hover{background:#236a58;color:white}#position{font-size:13px;color:var(--muted)}progress{display:block;width:200px;height:5px;accent-color:var(--green);margin-top:7px}.help,.site-footer{font-size:12px;text-align:center;color:var(--muted);margin:8px}.site-footer a{color:inherit}#outline{max-width:1320px;padding:20px;margin:15px auto;background:white;border:1px solid var(--line);border-radius:12px;display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:6px}#outline button{text-align:left}#outline button[aria-current=true]{background:var(--green);color:white}#notes{max-width:1200px;margin:20px auto;padding:25px;border:2px dashed #ad8248;background:#fff5df}#notes p{margin:8px 0}#notes small{color:#865921}.step-dots{display:flex;gap:5px;margin:15px 0}.step-dots i{display:block;width:20px;height:4px;background:#d6dfd4}.step-dots i.done{background:var(--green)}.case-link{font-size:13px;margin-top:15px}#handout{display:none}@keyframes fade-in{from{opacity:.3;transform:translateY(8px)}to{opacity:1;transform:translateY(0)}}.visual{animation:fade-in .2s ease}body:fullscreen{overflow:auto}#stage:focus{outline:none}
@media(min-width:1200px){.memory:has(.memory-cell:nth-child(8)){grid-template-columns:repeat(8,minmax(0,1fr))}}@media(max-width:760px){header{gap:8px;padding:12px;flex-wrap:wrap}.book{display:none}.tools{gap:4px}.tools button{font-size:11px;padding:6px}main{padding:18px 14px;min-height:60vh}.number{font-size:35px}.visual{padding:18px 14px}.bitrow{gap:7px}.bitrow>span{width:100%;font-size:14px}.bitgroup{gap:3px}.bit{min-width:28px;height:48px;font-size:22px}.formula{padding:14px;font-size:18px}.bullets{font-size:18px}.controls{padding:10px;flex-wrap:wrap}.controls>div:last-child{display:flex;gap:12px;align-items:center}progress{width:95px}.nav button{padding:8px 10px;font-size:13px}#outline{margin:10px;grid-template-columns:1fr}#notes{margin:10px}.question p,.answer,table{font-size:17px}td,th{padding:8px}.help{display:none}.memory-cell b{font-size:23px}}@media(prefers-reduced-motion:reduce){*,*::before,*::after{animation:none!important;scroll-behavior:auto!important}}
@media print{body>*{display:none!important}body>#handout{display:block!important;background:white;color:black;font-size:12pt}#handout section{break-before:page;padding:12mm}#handout h1{font-size:24pt}#handout h2{font-size:16pt}#handout .visual{box-shadow:none;animation:none;padding:12px;margin:10px 0}#handout .formula{font-size:14pt}#handout .bit{min-width:25px;height:38px;font-size:17px}#handout .bitrow>span{font-size:12pt}#handout table,#handout .conclusion,#handout .bullets{font-size:12pt}#handout .memory{grid-template-columns:repeat(8,1fr)}}

/* Chapter-based classroom and projection layout */
body{min-height:100dvh;display:flex;flex-direction:column}header{width:100%;max-width:1800px}main{flex:1;width:100%;max-width:1800px;min-height:0;display:flex;flex-direction:column;justify-content:center;padding-top:24px;padding-bottom:24px}.heading{margin-bottom:12px}.screen{align-items:center}.formula{font-size:clamp(19px,1.75vw,30px)}.visual{animation:none}.previous-step{font-size:14px;border:1px solid var(--line);border-radius:8px;padding:12px 18px;margin-top:12px;background:#eef2e8}.previous-step summary{cursor:pointer}.unit-navigation{display:flex;gap:18px;flex-wrap:wrap;font-size:14px;margin:18px 0 0}.unit-navigation a{padding:8px 0}.hint{padding:12px;background:#fff4db;color:#644b20}.question>button{margin-right:10px}.controls{width:100%}.help{margin:6px}.site-footer{margin:5px}.eyebrow b{white-space:nowrap}.quiz-list{margin-top:18px}.unit-navigation{grid-column:1/-1}
@media(min-width:1100px){.screen{grid-template-columns:minmax(0,1.55fr) minmax(280px,.9fr);gap:28px}.visual{min-height:clamp(320px,40vh,620px);display:flex;flex-direction:column;justify-content:center;padding:28px 32px}.bitrow>span{min-width:125px}.bit{min-width:clamp(36px,3vw,60px);height:clamp(60px,6vh,88px);font-size:clamp(26px,2.1vw,38px)}.bit small{font-size:12px}.formula{padding:24px}.formula mark{background:transparent}.question p{font-size:23px}.number{font-size:clamp(46px,4vw,75px)}}
@media(max-width:760px){.eyebrow{flex-wrap:wrap;gap:5px}.eyebrow b{white-space:normal}.controls .nav{gap:4px}.controls button{font-size:12px;padding:7px}.screen{grid-template-columns:1fr}.book{display:inline;font-size:12px}.tools{width:100%;margin:0}.question p{font-size:18px}}
@media print{#handout .screen{display:block}#handout .visual{min-height:0}body{display:block}}

@media(min-width:1500px){h1{font-size:clamp(48px,2.8vw,76px)}h2{font-size:clamp(30px,2vw,48px)}.visual{min-height:360px}.bit{min-width:clamp(46px,2.8vw,72px);height:90px;font-size:clamp(32px,2.1vw,54px)}.bitrow>span{font-size:21px}.formula{font-size:clamp(24px,1.6vw,38px)}.eyebrow{font-size:18px}}

.response-label{display:block;font-size:16px;margin:15px 0}.student-response{font:inherit;max-width:100%;padding:12px;border:1px solid #9aafa3;border-radius:6px;display:block;margin:8px 0;min-height:44px}.response-feedback{font-size:16px!important;color:#28593b}.embedded-experiment{margin:20px 0}.embedded-experiment button{margin:5px}.embedded-experiment iframe{display:block;width:100%;height:75vh;min-height:520px;border:1px solid var(--line);border-radius:12px;background:white}.embedded-experiment:has(iframe){flex:1}@media print{.embedded-experiment{display:none!important}}

.screen:has(>.concept-card){grid-template-columns:1fr}.screen>.concept-card{min-height:0;width:100%;padding:clamp(24px,3vw,48px)}.concept-explanation{font-size:clamp(20px,2vw,30px);line-height:1.8;max-width:48em;border-left:4px solid var(--accent,#285e4d);padding-left:24px}.concept-card .bullets{margin-top:28px}

.screen:has(>.shift-board){display:block}.shift-board{background:white;border:1px solid #ccdcd4;border-radius:16px;padding:clamp(16px,2vw,28px)}.shift-board h2{margin:0 0 16px}.shift-board p{line-height:1.7}.shift-comparison{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}.shift-option{padding:16px;background:#f2f5ee;border:2px solid transparent;border-radius:12px}.current{border-color:#285e4d;background:#e6f0d9}.shift-board .bitrow{flex-wrap:wrap;gap:8px}.shift-option .bitrow{display:block}.shift-option .bitgroup{gap:3px}.shift-option .bit{width:clamp(22px,2.5vw,38px);min-width:0}.shift-path,.source-rule{color:#245347;font-weight:700}.shift-work{display:grid;grid-template-columns:1.2fr 1fr;gap:24px}.weight-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:6px;margin-top:20px}.weight-cell{display:flex;flex-direction:column;gap:6px;padding:9px;background:#f5f5f3;border-bottom:3px solid #ddd}.weight-cell.included{background:#eef5e8;border-color:#547d40}.weight-cell small{font-size:13px}.weight-cell span{font-size:14px}.reason{padding:12px;border-left:3px solid #c7d5cd;margin:8px 0}.reason.current{border-color:#285e4d;font-weight:600}.next-preview{color:#466758;font-size:15px;margin-top:12px}.encoding-note{background:#f0f4eb;padding:8px 12px}
@media(max-width:900px){.shift-comparison,.shift-work{grid-template-columns:1fr}.shift-option .bit{width:30px}.weight-grid{grid-template-columns:repeat(2,minmax(0,1fr))}}

.shift-board h3{margin:8px 0;font-size:22px}.shift-board p{margin:8px 0;line-height:1.55}.shift-board .bitrow{margin:12px 0}.shift-board .bit{padding:5px 0}.shift-board .reason{padding:8px;margin:6px 0}.shift-board .weight-grid{margin-top:12px}.shift-board .weight-cell{padding:6px}.shift-option{padding:12px}.shift-board h2{font-size:28px}.shift-board .shift-work{gap:18px}

.extra-explanation{grid-column:1/-1;padding:14px 20px;border:1px solid #cedacf;border-radius:8px;margin-top:12px;line-height:1.8;background:#f4f6ef}.extra-explanation summary{cursor:pointer;font-size:18px}.key-explanation{font-size:clamp(24px,2.3vw,34px);font-weight:700;background:#edf4e5;padding:16px}.concept-card .bullets{font-size:clamp(21px,2vw,28px)}

.screen,.screen>*{min-width:0}.screen{overflow-wrap:anywhere}.table-wrap{max-width:100%;overflow-x:auto}.facts{min-width:0}.fact{min-width:0;overflow-wrap:anywhere}.formula mark{overflow-wrap:anywhere}