:root {
  --canvas:#edf0ec; --surface:#fafbf8; --ink:#173d39; --muted:#4e675b; --line:#ced8d0;
  --deep:#113c3b; --mint:#b6e0cc; --copper:#f0b77e; --board-muted:#a1c4b8;
  --mono:'Cascadia Mono','Cascadia Code',Consolas,'SFMono-Regular',monospace;
  --body:'Segoe UI','Microsoft YaHei UI','Microsoft YaHei',sans-serif;
  --display:Bahnschrift,'Arial Narrow','Microsoft YaHei UI',sans-serif;
  --text-body:1.125rem; --text-code:1.0625rem; --text-ui:1rem; --text-label:.875rem;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:90px}
body{margin:0;background:var(--canvas);color:var(--ink);font:var(--text-body)/1.7 var(--body)}
a{color:inherit;text-underline-offset:5px}
button,select,textarea{font:inherit}
button,a,select{touch-action:manipulation}
button{cursor:pointer}
button:disabled{cursor:default}
svg{display:block}
button:focus-visible,a:focus-visible,summary:focus-visible,select:focus-visible{outline:3px solid #bc671c;outline-offset:4px}
button:focus-visible{position:relative;z-index:3}
.skip-link{position:fixed;top:-80px;left:20px;z-index:99;padding:10px;background:var(--deep);color:white}
.skip-link:focus{top:12px}
.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}
.masthead{height:78px;max-width:1440px;margin:auto;display:flex;align-items:center;justify-content:space-between;padding:0 52px;border-bottom:1px solid var(--line)}
.brand{display:flex;align-items:center;gap:14px;text-decoration:none}
.brand-symbol{width:44px;height:44px}
.brand-type{font:600 23px/1 var(--display);letter-spacing:1.4px}
.brand-slash{font-weight:300;margin:0 5px;color:#7e9589}
.brand-type small{display:block;font:12px var(--mono);letter-spacing:1px;margin-top:8px;color:var(--muted)}
nav{display:flex;gap:30px;align-items:center}
nav a{font-size:var(--text-ui);min-height:44px;display:flex;align-items:center;text-decoration:none;gap:8px;white-space:nowrap}
nav a span{font-size:16px;color:var(--muted)}
nav a:hover{color:#9d5a2e}
.scope-link{border-left:1px solid var(--line);padding-left:30px}
main{max-width:1440px;margin:auto;padding:26px 52px 24px}
.intro{display:flex;justify-content:space-between;align-items:center;margin-bottom:22px}
.eyebrow{display:flex;gap:9px;align-items:center;margin:0 0 8px;font-size:11px;color:var(--muted);letter-spacing:1.4px}
.eyebrow>span{width:5px;height:5px;background:#6a9181;border-radius:1px}
h1{font-size:clamp(29px,3vw,38px);line-height:1.3;font-weight:650;letter-spacing:-1.5px;margin:0}
h1>span{font-weight:400;margin-left:4px}
.intro-description{font-size:var(--text-body);color:var(--muted);margin:10px 0 0}
.intro-aside{text-align:right}
.technical-mark{font:300 59px/1 var(--display);letter-spacing:-3px;color:#9caf9e}
.technical-mark>span{color:#b07b4d}
.intro-aside p{font-size:10px;color:var(--muted);margin:7px 0 0}
.intro-aside i,.editor-caption i{display:inline-block;background:#5d927b;width:5px;height:5px;border-radius:50%;margin-right:6px}
.lesson-bar{display:flex;align-items:center;gap:22px;margin-bottom:16px;min-height:61px;border-top:1px solid var(--line);border-bottom:1px solid var(--line)}
.lesson-label{display:flex;flex-direction:column;min-width:82px}
.lesson-label>span{font-size:var(--text-label);font-weight:600}
.lesson-label small{font:var(--text-label) var(--mono);color:var(--muted);margin-top:3px}
.lesson-tabs{display:flex;gap:6px;flex:1}
.lesson-tab{display:flex;align-items:center;gap:8px;border:1px solid transparent;background:none;color:var(--muted);font-size:var(--text-ui);min-height:48px;padding:10px 14px;border-radius:4px;white-space:normal;text-align:left;transition:background .18s,color .18s}
.lesson-tab small{font:10px var(--mono);opacity:.65}
.lesson-tab:hover{background:#e0e7df;color:var(--ink)}
.lesson-tab[aria-pressed=true]{background:var(--deep);color:#e5f1e7;border-color:var(--deep)}
.mobile-lesson{display:none;min-width:0}
.mobile-lesson select{min-height:48px;width:100%;border:1px solid var(--line);background:var(--surface);color:var(--ink);border-radius:4px;padding:8px 12px;font-size:var(--text-ui)}
.workbench{scroll-margin-top:16px}
.control-bar{display:flex;justify-content:space-between;align-items:center;margin-bottom:13px;gap:12px}
.controls{display:flex;gap:7px}
.controls button{display:flex;align-items:center;justify-content:center;gap:8px;border:1px solid #bdccc1;border-radius:4px;min-height:48px;padding:10px 14px;background:#f6f8f3;color:var(--ink);font-size:var(--text-ui);transition:background .18s,box-shadow .18s}
.controls button svg{width:16px;height:16px;fill:none;stroke:currentColor;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:round}
.controls button.primary{background:var(--deep);border-color:var(--deep);color:#edf8ef;box-shadow:0 2px 3px #143b3420}
.controls button.primary:hover:not(:disabled){background:#1d5550;box-shadow:0 3px 8px #143b342d}
.controls button:hover:not(:disabled){background:#dfe9df}
.controls button:active:not(:disabled){box-shadow:inset 0 1px 3px #143b3440}
.controls button:disabled{opacity:.37}
.controls .quiet{border-color:transparent;background:transparent}
.controls kbd{font:var(--text-label) var(--mono);border:1px solid #ffffff38;padding:1px 4px;border-radius:2px;margin-left:4px;color:var(--mint)}
.session-state{font:var(--text-label) var(--mono);color:var(--muted);letter-spacing:1px;display:flex;align-items:center;gap:7px}
.session-state i{width:5px;height:5px;border-radius:50%;background:#709d84}
.session-state i.running{background:#b57b3b;box-shadow:0 0 0 3px #c78b4a20;animation:led-breathe 1s infinite}
.workspace{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1.1fr);gap:20px;align-items:stretch}
.editor-panel{background:var(--surface);border:1px solid #c8d3c9;border-radius:6px;overflow:hidden;min-width:0;box-shadow:0 3px 5px #173d3904}
.panel-title{display:flex;align-items:center;justify-content:space-between;padding:17px 20px;gap:12px}
.panel-title>div{display:flex;align-items:center;gap:10px}
.section-tag{font:12px var(--mono);letter-spacing:1px;color:var(--muted)}
h2,h3{font-size:var(--text-body);font-weight:600;line-height:1.5;margin:0}
.file-label{font:var(--text-label) var(--mono);color:var(--muted);display:flex;align-items:center;gap:6px}
.file-label i{height:5px;width:5px;background:#b5c5b4;border-radius:1px}
.code-editor{position:relative;height:350px;background:#f4f7f1;border-top:1px solid #e0e7de;border-bottom:1px solid #e0e7de;overflow:hidden}
.code-editor textarea,.code-editor pre{position:absolute;inset:0;margin:0;border:0;font:var(--text-code)/32px var(--mono);padding:18px 20px 24px 58px;tab-size:2;white-space:pre;overflow:auto;letter-spacing:0;word-spacing:0}
.code-editor textarea{resize:none;color:transparent;background:transparent;caret-color:#153f39;width:100%;height:100%;z-index:2;-webkit-text-fill-color:transparent}
.code-editor textarea::selection{background:#b1d9c077}
.code-editor textarea:focus-visible{outline:2px solid #78a58f;outline-offset:-2px}
.code-editor pre{pointer-events:none;color:#35574a;scrollbar-width:none}
.code-editor pre::-webkit-scrollbar{display:none}
.line-numbers{position:absolute;z-index:1;left:0;top:18px;width:40px;text-align:right;pointer-events:none;font:var(--text-label)/32px var(--mono);color:#607363;white-space:pre}
.token-op{color:#206969;font-weight:600}.token-number{color:#9a5c2c}.token-comment{color:#566e5c}.token-label{color:#7b5a83}
.editor-caption{display:flex;justify-content:space-between;flex-wrap:wrap;gap:6px 12px;padding:12px 18px;color:var(--muted);font-size:var(--text-label)}
.status{font-size:var(--text-ui);line-height:1.7;color:var(--muted);min-height:62px;padding:10px 20px 16px;overflow-wrap:anywhere}
.status.error{color:#a13d2b}
.next-instruction{background:#eaf0e7;display:flex;align-items:center;gap:12px;padding:14px 20px;border-top:1px solid #dce5d9;font-size:var(--text-label);color:#52745f}
.next-instruction code{font:var(--text-ui) var(--mono);color:#2e5945;flex:1;min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.next-instruction>span:last-child{font:var(--text-label) var(--mono);color:var(--muted)}
.execution{border-top:1px solid #dce5d9}
.execution summary{cursor:pointer;font-size:var(--text-ui);padding:12px 20px;min-height:48px;color:var(--muted)}
.execution summary>span{float:right;color:#718774}
#listing{list-style:none;padding:0 12px 9px;margin:0;max-height:260px;overflow:auto;font:var(--text-ui)/1.8 var(--mono)}
#listing li{display:flex;gap:12px;padding:5px 8px;border-left:2px solid transparent}
#listing li.current{background:#d8e9da;border-left-color:#40846b;color:#24593e}
#listing li.previous{background:#eef1e8}
#listing li span{color:#718774;min-width:20px}
#listing li b{margin-left:auto;font:var(--text-label) var(--body);white-space:nowrap}
.processor{position:relative;background:var(--deep);color:#e5f3e8;border-radius:6px;border:1px solid #0a3030;padding:20px 25px 0;box-shadow:0 5px 10px #0b343012,inset 0 1px 0 #ffffff14;min-width:0;overflow:hidden}
.processor:before,.processor:after{content:'';position:absolute;top:91px;bottom:88px;width:5px;background:repeating-linear-gradient(180deg,#8da59760 0,#8da59760 3px,transparent 3px,transparent 17px);pointer-events:none}
.processor:before{left:0}.processor:after{right:0}
.processor-top{display:flex;justify-content:space-between;align-items:start}
.processor-top>div{display:flex;gap:10px;align-items:center}
.processor .section-tag{color:var(--board-muted)}
.processor h2{font-size:var(--text-body);font-weight:500}
.processor-model{font:17px/1.1 var(--display);letter-spacing:2px;color:#d6e9da;text-align:right}
.processor-model>span{font:12px var(--mono);letter-spacing:.5px;color:var(--board-muted);display:block;margin-top:4px}
.signal-diagram{display:grid;grid-template-columns:minmax(0,1fr) 42px minmax(0,1fr);align-items:center;gap:8px;margin:16px 0 18px}
.signal-label{display:grid;place-items:center;min-height:52px;padding:8px;border:1px solid #497269;border-radius:4px;background:#174543;color:#d1e6d9;text-align:center;overflow-wrap:anywhere;font:var(--text-label)/1.5 var(--mono)}
.signal-map{width:42px;height:30px;overflow:visible}
.signal-track{fill:none;stroke:#53776b;stroke-width:1}
.signal-flow{fill:none;stroke:var(--copper);stroke-width:2;stroke-dasharray:4 8;opacity:0}
.signal-node{fill:#a1c7ab}
.readout{padding:0 0 14px;border-bottom:1px solid #42645b}
.readout-heading{display:flex;justify-content:space-between;align-items:center}
.readout-heading>span:first-child{display:flex;align-items:center;gap:9px}
.readout-heading b{font:var(--text-body) var(--mono);color:var(--mint);letter-spacing:1px}
.readout-heading>span>span{font-size:var(--text-label);color:var(--board-muted)}
.readout-unit{font:var(--text-label) var(--mono);color:var(--board-muted);letter-spacing:.5px}
.readout-value{display:flex;align-items:baseline;justify-content:space-between;gap:15px;margin-top:1px}
.readout-value>strong{font:500 clamp(54px,6vw,68px)/1.25 var(--mono);letter-spacing:5px;color:#d2ecd4;font-variant-numeric:tabular-nums;text-shadow:0 0 24px #a0dcb310}
.readout-value>span{font:var(--text-label) var(--mono);color:var(--board-muted);text-align:right}
.readout-value>span.changed-text{color:var(--copper)}
.value-interpretations{display:flex;flex-wrap:wrap;gap:6px 24px;font-size:var(--text-ui);color:var(--board-muted);margin-top:4px}
.value-interpretations b{font:var(--text-body) var(--mono);color:#d1e3d2;margin-left:7px}
.bit-labels{display:flex;justify-content:space-between;font:var(--text-label) var(--mono);letter-spacing:1px;color:#9bc0ae;margin-top:16px;margin-bottom:7px}
.bit-strip{display:grid;grid-template-columns:repeat(16,1fr);gap:4px}
.bit-strip>span{height:26px;border:1px solid #476b5d;background:#234b43;color:#a1c6b0;display:grid;place-items:center;font:var(--text-label) var(--mono);border-radius:1px;transition:background .2s,color .2s}
.bit-strip>span:nth-child(4n){margin-right:4px}
.bit-strip>span.on{background:#abd1b2;border-color:#bdddc0;color:#183e32}
.bit-strip>span.bit-changed{background:var(--copper);border-color:#f8c491;color:#4b301b}
.register-caption{display:flex;justify-content:space-between;align-items:center;font-size:var(--text-label);color:var(--board-muted);margin:14px 0 10px}
.register-caption>span:last-child{display:flex;align-items:center;gap:5px}
.register-caption i{height:4px;width:4px;background:var(--copper);border-radius:1px}
.registers{display:grid;grid-template-columns:repeat(4,1fr);gap:5px}
.register-cell{display:flex;align-items:center;justify-content:space-between;gap:8px;min-height:50px;padding:9px;border:1px solid #41675b;border-radius:3px;background:#16403c;color:#c5dbca;text-align:left;transition:background .18s,border .18s}
.register-cell:hover{background:#245348;border-color:#93b29c}
.register-cell>span{font:var(--text-label) var(--mono);color:#a5c4b1}
.register-cell>strong{font:var(--text-body) var(--mono);font-weight:400;letter-spacing:0}
.register-cell[aria-pressed=true]{background:#325d4c;border-color:#90bda0}
.register-cell[aria-pressed=true]>span{color:#e5efdb}
.register-cell.changed>strong{color:var(--copper)}
.flags-heading{display:flex;align-items:center;justify-content:space-between;margin-top:12px;margin-bottom:8px}
.flags-heading h3{font-size:var(--text-ui);color:var(--board-muted);font-weight:400}
.flags-heading>span{font-size:var(--text-label);color:var(--board-muted)}
.flags{display:grid;grid-template-columns:repeat(6,1fr);gap:5px}
.flag{text-align:center;border:1px solid #41675b;border-radius:3px;background:#153e39;position:relative;padding:5px 2px}
.flag>span{display:block;font:var(--text-label) var(--mono);color:#a5c4b1}
.flag>strong{font:22px/1.5 var(--mono);font-weight:400;color:#a5c4b1}
.flag.active>strong{color:#def0cc}
.flag.active{background:#2a5345}
.flag.changed{border-bottom:2px solid var(--copper);padding-bottom:4px}
.flag.changed>strong{color:var(--copper)}
.segments{display:flex;flex-wrap:wrap;justify-content:space-between;gap:8px;margin:18px -25px 0;padding:14px 25px;border-top:1px solid #42645b;background:#0d3432;color:#98baa7;font:var(--text-label) var(--mono)}
.segments b{font-weight:400;margin-left:7px;color:#bdd8bd}
.notes-grid{display:grid;grid-template-columns:1fr 1.1fr;gap:20px;margin-top:20px}
.observation,.memory-panel{background:#f7f9f4;border:1px solid var(--line);border-radius:6px;overflow:hidden;min-width:0}
.observation .panel-title,.memory-panel .panel-title{padding-bottom:10px}
.observation-symbol{font:23px var(--display);color:#8da991}
.observation>p{font:var(--text-body)/1.8 var(--body);margin:0 20px 17px;color:#325d4b;overflow-wrap:anywhere;min-height:46px}
.lesson-insight{display:flex;gap:12px;border-top:1px solid #dce4d8;padding:14px 20px;background:#e9efe3}
.lesson-insight>span{white-space:nowrap;font-size:var(--text-label);color:#647c61;padding-top:2px}
.lesson-insight p{font-size:var(--text-ui);line-height:1.8;margin:0;color:#4a674a}
.memory-unit{font:12px var(--mono);color:var(--muted);letter-spacing:.5px}
#memory{padding:0 20px;max-height:280px;overflow:auto}
.memory-empty{display:flex;gap:16px;align-items:center;padding:12px 0 15px;min-height:94px}
.memory-empty svg{width:79px;flex-shrink:0;color:#a3b49e}
.memory-empty p{font-size:var(--text-ui);line-height:1.8;color:var(--muted);margin:0}
.memory-empty button{display:block;background:none;border:0;padding:0;min-height:44px;font-size:var(--text-ui);text-decoration:underline;text-underline-offset:4px;color:#3e765e}
.memory-note{font-size:var(--text-label);color:var(--muted);margin:0 20px 13px}
.micro{font-size:var(--text-label);color:var(--muted);line-height:1.7;margin:4px 0 7px}
table{width:100%;border-collapse:collapse;font:var(--text-ui)/1.8 var(--mono)}
td,th{text-align:left;padding:5px 8px;border-bottom:1px solid #dfe7db}
th{font-size:var(--text-label);color:var(--muted);font-weight:400}
tr.changed td{background:#f3e5d2;color:#835b32}
.scope{margin-top:24px;border-top:1px solid var(--line);border-bottom:1px solid var(--line);font-size:var(--text-ui);color:var(--muted)}
.scope summary{display:flex;justify-content:space-between;align-items:center;cursor:pointer;list-style:none;min-height:57px;font-size:var(--text-ui);color:var(--ink)}
.scope summary::-webkit-details-marker{display:none}
.scope summary>span{font-size:var(--text-label);color:var(--muted)}
.scope summary b{font:19px var(--mono);font-weight:300;margin-left:16px}
.scope details[open] summary b{display:inline-block;transform:rotate(45deg)}
.scope details>div{padding:0 0 15px;max-width:1060px}
.scope code{font:var(--text-ui)/2 var(--mono);overflow-wrap:anywhere}
footer{display:flex;align-items:center;justify-content:space-between;gap:20px;padding:24px 0 0;font:var(--text-label) var(--mono);letter-spacing:.8px;color:var(--muted)}
.footer-brand{font:var(--text-label) var(--display);font-weight:600;text-decoration:none;letter-spacing:1.7px}
.footer-brand>span{font:10px var(--body);font-weight:400;letter-spacing:0;margin-left:17px;color:var(--muted)}
.footer-dot{margin:0 10px}
@keyframes led-breathe{50%{box-shadow:0 0 0 4px #d2ae6120}}
@media(max-width:1100px){
  .masthead{padding:0 30px}main{padding-left:30px;padding-right:30px}
  .lesson-bar{gap:15px}.lesson-tab{padding:8px 9px;gap:6px}.lesson-label{min-width:67px}
  .processor{padding-left:18px;padding-right:18px}.segments{margin-left:-18px;margin-right:-18px;padding-left:18px;padding-right:18px}
  .workspace{grid-template-columns:minmax(0,1fr)}.processor{grid-row:1}
  .readout-value>strong{font-size:72px}.panel-title{padding-left:18px;padding-right:18px}
  .panel-title>div{gap:7px}.memory-unit{display:none}
  .control-bar{flex-wrap:wrap}.control-links{margin-left:auto}
}
@media(max-width:850px){
  .workspace{grid-template-columns:minmax(0,1fr)}.processor{grid-row:1;padding-left:25px;padding-right:25px}
  .readout-value>strong{font-size:80px}.readout{padding-bottom:16px}
  .segments{margin-left:-25px;margin-right:-25px;padding-left:25px;padding-right:25px}
  .notes-grid{grid-template-columns:1fr}
  .control-bar{position:sticky;top:0;background:var(--canvas);z-index:20;padding:10px 0;margin-top:-10px;border-bottom:1px solid var(--line)}
  .lesson-label{display:none}
  .lesson-tabs{justify-content:space-between}.lesson-tab{flex:1;justify-content:center;gap:5px}
  .lesson-bar{min-height:61px}.intro-aside{display:none}.intro{margin-bottom:23px}.masthead{height:84px}
  nav{gap:22px}.scope-link{padding-left:22px}
  .memory-empty{flex-direction:column;align-items:flex-start;gap:6px}.memory-empty svg{width:62px;height:38px}
  .lesson-insight{display:block}.lesson-insight>span{display:block;margin-bottom:5px}
}
@media(max-width:560px){
  html{scroll-padding-top:165px}
  .masthead{padding:14px 16px;min-height:78px;height:auto;gap:8px;flex-wrap:wrap}.brand-symbol{width:35px;height:35px}.brand{gap:9px;flex-shrink:0}
  .brand-type{font-size:21px}.brand-type small{display:none}
  nav{gap:12px;margin-left:auto}nav a{font-size:var(--text-label)}nav a span{display:none}.scope-link{display:none}main{padding:26px 16px 20px}
  h1{font-size:32px;letter-spacing:-1px}h1>span{margin-left:0}
  .intro-description{margin-top:9px}.lesson-tabs{display:none}.lesson-label{display:flex;min-width:64px}
  .mobile-lesson{display:block;flex:1}.lesson-bar{gap:12px;padding:12px 0;margin-bottom:16px;min-height:65px}
  .controls{display:grid;grid-template-columns:1fr 1fr;gap:8px;width:100%}.controls button{padding:10px;gap:8px}
  .controls button svg{width:18px;height:18px}.controls kbd{display:none}.session-state{display:none}
  .processor{padding:17px 17px 0}.processor-top>div{gap:8px}.processor-model{font-size:15px}
  .processor .section-tag,.processor-model>span{display:none}
  .readout-value{flex-wrap:wrap;gap:0 10px}.readout-value>strong{font-size:64px;letter-spacing:3px}
  .readout-value>span{margin-bottom:8px}.readout-unit{letter-spacing:0}
  .bit-strip{gap:2px}.bit-strip>span:nth-child(4n){margin-right:1px}
  .registers{grid-template-columns:repeat(2,1fr);gap:8px}.register-cell{min-height:52px;padding:10px}.register-cell>strong{font-size:20px}
  .segments{margin-left:-17px;margin-right:-17px;padding:14px 17px}.segments b{margin-left:4px}
  .notes-grid{grid-template-columns:1fr;gap:14px;margin-top:14px}.memory-empty{flex-direction:row;align-items:center;gap:17px;min-height:90px}
  .memory-empty svg{width:70px;height:52px}.lesson-insight{display:flex;gap:12px}.lesson-insight>span{margin-bottom:0}
  .panel-title{padding:16px 17px 12px}.observation>p{margin-left:17px;margin-right:17px;min-height:auto}.workspace{gap:14px}
  .section-tag,.file-label{display:none}
  .code-editor textarea,.code-editor pre{padding-left:48px;padding-right:14px}.line-numbers{width:32px}
  .execution summary>span{float:none;display:block}.next-instruction{padding-left:17px;padding-right:17px;gap:8px}
  .scope{margin-top:22px}.scope summary>span{display:none}
  footer{align-items:flex-start;padding-top:20px}footer>span{text-align:right;line-height:1.8}
  .footer-dot{margin:0 5px}
}
[hidden]{display:none!important}
.chapter-picker{display:grid;grid-template-columns:auto minmax(0,1fr) auto auto;align-items:center;gap:12px;margin:0 0 18px;font-size:var(--text-ui)}
.chapter-picker label{font-weight:600}
.chapter-picker select{width:100%;min-width:0;min-height:48px;padding:10px 12px;color:var(--ink);border:1px solid #bdccc1;border-radius:4px;background:var(--surface);font-size:var(--text-ui)}
.chapter-picker a{white-space:nowrap;text-decoration:none;padding:10px 0}
.chapter-picker button,.reading-panel button{min-height:48px;border:1px solid #bdccc1;border-radius:4px;background:var(--surface);padding:10px 12px;color:var(--ink);font-size:var(--text-ui)}
#route-message{grid-column:2/-1;font-size:var(--text-label);color:var(--muted);overflow-wrap:anywhere}
#route-message:empty{display:none}
.lesson-tabs{flex-wrap:wrap}
.control-links{display:flex;align-items:center;gap:18px;font-size:var(--text-label);color:var(--muted)}
.control-links>a{text-decoration:none}
.reading-panel{padding:24px;background:var(--surface);border:1px solid var(--line);border-radius:6px;margin:20px 0}
.reading-panel h2{font-size:22px}
.reading-panel p{font-size:var(--text-body);max-width:760px;color:var(--muted);margin:12px 0 18px}
.reading-panel a{font-size:var(--text-ui);margin-right:24px}
.demo-guide{padding:20px;background:var(--surface);border:1px solid var(--line);border-radius:6px;margin-top:20px;scroll-margin-top:80px}
.guide-heading{display:flex;justify-content:space-between;gap:16px;align-items:baseline}
.guide-heading h2{font-size:20px;flex-shrink:0}
.guide-heading a{font-size:var(--text-ui);text-decoration:none;text-align:right}
#source-section{font-size:var(--text-ui);color:var(--muted);margin:10px 0 18px}
.guide-columns{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1.2fr);gap:24px}
#demo-steps{font-size:var(--text-body);margin:0;padding-left:24px;line-height:1.8}
#demo-steps li{padding:3px 0 7px 3px}
#demo-checkpoints{display:grid;gap:7px}
.checkpoint{display:flex;flex-direction:column;gap:6px;min-height:72px;width:100%;text-align:left;padding:12px 14px;border:1px solid var(--line);border-radius:4px;background:#f0f5ed;color:var(--ink)}
.checkpoint strong{font-size:var(--text-ui);font-weight:600}
.checkpoint span{font-size:var(--text-body);line-height:1.7}
.checkpoint:hover:not(:disabled){border-color:#72957f;background:#e7f0e2}
.checkpoint.checkpoint-current{border-color:#51856a;background:#dfeeda}
.checkpoint.checkpoint-past{background:#f6f8f2}
.checkpoint:disabled{opacity:.5}
#demo-edited-note,#demo-scope{font-size:var(--text-ui);line-height:1.8;color:var(--muted)}
#demo-scope{border-top:1px solid var(--line);padding-top:12px;margin:15px 0 0}
.chapter-index{border-top:1px solid var(--line);margin-top:24px;padding:10px 0}
.chapter-index summary{min-height:48px;padding:12px 0;cursor:pointer;font-size:var(--text-ui)}
.chapter-index ol{list-style:none;display:grid;grid-template-columns:1fr 1fr;gap:8px;margin:10px 0 0;padding:0}
.chapter-index button{display:flex;align-items:center;justify-content:space-between;gap:16px;min-height:52px;width:100%;padding:12px;text-align:left;background:var(--surface);border:1px solid var(--line);border-radius:4px;color:var(--ink);font-size:var(--text-ui)}
.chapter-index small{white-space:nowrap;color:var(--muted);font-size:var(--text-label)}
.intro h1{font-size:32px}
@media(max-width:850px){.control-links .session-state{display:none}.guide-columns{gap:16px}.guide-heading{align-items:flex-start}}
@media(max-width:560px){.chapter-picker{grid-template-columns:1fr 1fr;gap:8px 12px}.chapter-picker label{grid-column:1/-1}.chapter-picker select{grid-column:1/-1}.chapter-picker button{justify-self:end}.chapter-picker #route-message{grid-column:1/-1}.control-bar{flex-wrap:wrap}.controls{width:100%}.control-links{width:100%;justify-content:flex-end}.guide-heading{display:block}.guide-heading a{display:block;text-align:left;margin-top:8px;line-height:1.7}.demo-guide{padding:18px;scroll-margin-top:165px}.guide-columns{grid-template-columns:1fr;gap:16px}.chapter-index ol{grid-template-columns:1fr}.intro h1{font-size:30px}.reading-panel{padding:18px}.reading-panel button{display:block;margin-top:12px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*:before,*:after{transition:none!important;animation:none!important}}