body[data-mode=chapter4]{overflow:auto;height:auto;min-height:100dvh;background:var(--chapter-bg)}
body[data-mode=chapter4] #world,body[data-mode=chapter4] #vignette{display:none}
body[data-mode=chapter4] #app{height:auto;min-height:100dvh;padding-bottom:20px;background:var(--chapter-bg)}
body[data-mode=chapter4] .topbar{height:62px;background:var(--chapter-deep);padding:6px 24px}
body[data-mode=chapter4] button,body[data-mode=chapter4] select,body[data-mode=chapter4] input[type=number],body[data-mode=chapter4] summary{min-height:44px}
body[data-mode=chapter4] button:focus-visible,body[data-mode=chapter4] input:focus-visible,body[data-mode=chapter4] select:focus-visible,body[data-mode=chapter4] summary:focus-visible{outline:3px solid var(--cream);outline-offset:3px}
body[data-mode=chapter4] button:disabled{opacity:.5}
body[data-mode=chapter4] .primary{background:var(--chapter-accent);color:var(--chapter-deep);font-size:14px;box-shadow:0 3px 0 var(--chapter-accent-shadow)}
body[data-mode=chapter4] .secondary{background:var(--chapter-surface);color:var(--chapter-text);border:1px solid var(--chapter-border);font-size:13px}
.c4-map{max-width:650px;margin:6vh auto;padding:32px;border:1px solid var(--chapter-border);border-radius:22px;background:var(--chapter-panel)}
.c4-map h1{font-size:clamp(28px,4vw,48px);margin:18px 0}.c4-map p{color:var(--chapter-muted);line-height:1.5}.c4-map>.primary,.c4-map>.secondary{margin:18px 8px 10px 0}.c4-map .mission-menu{margin:24px 0}
.c4-workspace{max-width:1600px;padding:0 24px;margin:auto}.c4-heading{display:flex;justify-content:space-between;align-items:center;gap:30px;padding:18px 0}.c4-heading h1{font-size:26px;margin:5px 0 0;letter-spacing:-.5px}.c4-heading .eyebrow{color:var(--cream);font-size:10px}.c4-heading p{max-width:340px;font-size:13px;line-height:1.5;color:var(--chapter-muted)}
.c4-layout{display:grid;grid-template-columns:minmax(0,1.45fr) minmax(340px,1fr);gap:16px;align-items:start}
.c4-world-panel,.c4-editor-panel,.c4-execution{border:1px solid var(--chapter-border);border-radius:18px;overflow:hidden;background:var(--chapter-panel);min-width:0}
.c4-world-panel{grid-column:1;background:var(--chapter-panel)}.c4-panel-label{display:flex;align-items:center;justify-content:space-between;gap:12px;min-height:44px;padding:10px 16px;font-size:10px;letter-spacing:1.2px;color:var(--chapter-muted)}.c4-panel-label h2{font-size:16px;letter-spacing:0;color:var(--chapter-text)}.c4-panel-label strong{color:var(--cream);font-size:12px;letter-spacing:0;font-weight:600}
#c4-junction{line-height:0}#c4-junction>svg{display:block;width:100%;height:auto;max-width:none;max-height:none}.c4-road-caption{display:flex;justify-content:space-between;gap:12px;padding:10px 14px;font-size:11px;color:var(--chapter-muted);background:var(--chapter-deep);line-height:1.4}
.c4-mobile-tabs{display:none}.c4-program{grid-column:2;grid-row:1 / span 2}.c4-electronics{grid-column:1;grid-row:2}.c4-edit-footer{grid-column:1/-1;display:flex;align-items:center;justify-content:space-between;gap:16px;padding:14px 18px;border-radius:14px;background:var(--chapter-deep);border:1px solid var(--chapter-border)}.c4-edit-footer>div{display:flex;align-items:center;gap:12px;flex-shrink:0}.c4-edit-footer .primary{min-width:160px}.c4-feedback{font-size:13px;color:var(--cream);line-height:1.5}.c4-feedback:empty{display:none}
/* Illustrated component choice, then a simplified circuit without a breadboard. */
.c4-component-tray{display:flex;align-items:stretch;gap:10px;margin:0 14px 12px}.c4-component-tray .inventory{display:flex;align-items:center;gap:12px;padding:8px 12px;flex:1;min-width:0}.c4-component-tray .part-drawing{width:80px;height:56px;flex-shrink:0}.c4-component-tray svg{width:80px;height:56px}.c4-component-tray .inventory>span:not(.part-drawing){text-align:left;font-size:13px}.c4-component-tray small{display:block;margin-top:4px;font-size:11px}.c4-component-tray b{margin-left:auto}.c4-power{background:var(--chapter-deep);border:1px solid var(--chapter-border);border-radius:10px;padding:8px 12px;font-size:11px;color:var(--chapter-muted)}.c4-power strong{display:block;color:var(--chapter-text);font-size:12px;margin-top:4px}
#c4-circuit{margin:0 14px;border-radius:12px;background:var(--chapter-board);overflow:hidden}#c4-circuit svg{display:block;width:100%;height:auto;max-height:370px}.c4-wiring{display:grid;grid-template-columns:repeat(auto-fit,minmax(230px,1fr));gap:10px;padding:12px 14px}.c4-connection{padding:10px;border-radius:10px;background:var(--chapter-deep);display:grid;grid-template-columns:1fr auto;align-items:center;gap:8px}.c4-connection b{font-size:13px;color:var(--cream)}.c4-connection small{display:block;font-size:11px;line-height:1.4;color:var(--chapter-muted);margin-top:5px}.c4-connection .secondary{padding:6px 12px}.c4-connection details{grid-column:1/-1;font-size:12px;border-top:1px solid var(--chapter-border)}.c4-connection summary{cursor:pointer;align-content:center;color:var(--chapter-muted);padding:8px 0}.c4-connection details>div{display:flex;flex-wrap:wrap;gap:10px}.c4-connection label{display:flex;align-items:center;gap:8px;min-height:44px}.c4-connection select{max-width:130px;border:1px solid var(--chapter-border);border-radius:6px;background:var(--chapter-surface);color:var(--chapter-text);font:inherit;padding:4px}.c4-connection input[type=checkbox],.c4-repeat input{width:22px;height:22px;accent-color:var(--chapter-accent)}.c4-guide{padding:0 16px 16px;font-size:12px;line-height:1.5;color:var(--chapter-muted)}
/* Connected instruction shapes; words and outlines distinguish output, wait and repeat. */
.c4-loop{margin:0 14px 12px;padding:8px 4px}.c4-loop.is-loop{border:2px solid var(--cream);border-right:0;border-radius:14px 0 0 14px;padding:0 6px 0 12px;background:var(--chapter-deep)}.c4-loop-label,.c4-loop-return{font-size:12px;color:var(--cream);padding:12px 4px}.c4-loop-label{font-weight:700}.c4-blocks{list-style:none;margin:0;padding:6px 4px 12px;max-height:470px;overflow:auto;overscroll-behavior:contain;scrollbar-width:thin;scrollbar-color:var(--chapter-muted) var(--chapter-deep);display:flex;flex-direction:column;gap:11px}.c4-block{position:relative;border:1px solid var(--chapter-border);border-radius:8px 12px 12px 8px;background:var(--chapter-output);color:var(--chapter-text);flex-shrink:0;box-shadow:0 3px 0 var(--chapter-shadow)}.c4-block:before{content:"";position:absolute;top:-6px;left:27px;width:29px;height:8px;border-radius:0 0 5px 5px;background:var(--chapter-panel);border:1px solid var(--chapter-border);border-top:0}.c4-block:after{content:"";position:absolute;bottom:-7px;left:27px;width:29px;height:8px;border-radius:0 0 5px 5px;background:inherit;border:1px solid var(--chapter-border);border-top:0;z-index:1}.c4-wait{background:var(--chapter-wait);border-left:5px solid var(--cream);border-radius:8px 20px 20px 8px}.c4-gap{border:2px dashed var(--chapter-muted);background:var(--chapter-deep)}.c4-block.fault{outline:3px solid #ffc2a5;outline-offset:1px}.c4-block-main{display:flex;align-items:center;gap:9px;padding:8px}.c4-block-number{width:18px;text-align:center;color:var(--chapter-muted);font-size:11px;flex-shrink:0}.c4-block-copy{flex:1;min-width:0;font-size:15px;line-height:1.5}.c4-block-copy>small{display:block;font-size:9px;letter-spacing:1px;color:var(--chapter-muted)}.c4-block-copy label{display:flex;align-items:center;gap:7px;flex-wrap:wrap}.c4-chip{border-radius:7px;min-width:44px;background:var(--chapter-deep);border:1px solid var(--chapter-border);padding:3px 9px;font:inherit;color:var(--cream);vertical-align:middle}.c4-chip:disabled{opacity:1!important}.c4-block-copy input{width:58px;background:var(--chapter-deep);color:var(--cream);border:1px solid var(--chapter-border);border-radius:7px;font:inherit;padding:5px;text-align:center}.c4-block-more{min-width:44px;width:44px;color:var(--chapter-text);font-size:24px;align-self:center}.c4-block-tools{display:flex;gap:8px;padding:8px;border-top:1px solid var(--chapter-border);background:var(--chapter-deep)}.c4-block-tools[hidden]{display:none}.c4-block-tools button{flex:1;font-size:12px;border:1px solid var(--chapter-border);border-radius:7px;background:var(--chapter-deep)}.c4-gap-choices{display:flex;gap:6px;flex-wrap:wrap}.c4-gap-choices button{font-size:12px;background:var(--chapter-surface);border:1px solid var(--chapter-border);padding:6px;border-radius:6px;flex:1}.c4-empty{font-size:14px;color:var(--chapter-muted);padding:24px 8px}.c4-add{display:flex;gap:8px;padding:0 14px 14px}.c4-add button{flex:1;padding:8px 6px;border:1px solid var(--chapter-border);border-radius:9px;background:var(--chapter-deep);font-size:12px}.c4-repeat{display:flex;align-items:center;gap:10px;min-height:48px;padding:8px 14px;margin:0 14px 14px;border-radius:10px;background:var(--chapter-deep);font-size:13px;color:var(--cream)}
/* Running uses its own normal-flow layout. No scene floats over the editor. */
.c4-watching .c4-layout{grid-template-columns:minmax(0,1fr) 310px;align-items:start}.c4-execution{display:flex;flex-direction:column;grid-column:2;min-width:0}.c4-execution-readings{padding:0 14px;min-height:0;overflow:auto}.c4-current{padding:16px;border:2px solid var(--cream);border-radius:12px;background:var(--chapter-deep);margin-bottom:16px}.c4-current>small{font-size:10px;color:var(--cream);letter-spacing:1px}.c4-current h2{font-size:21px;line-height:1.3;margin:8px 0 10px}.c4-current>span{display:block;font-size:12px;color:var(--chapter-muted)}.c4-current progress{width:100%;height:9px;accent-color:var(--chapter-accent);display:block;margin:12px 0 7px;border:0;border-radius:5px;overflow:hidden;background:var(--chapter-surface)}.c4-current progress[hidden]{display:none}.c4-current progress::-webkit-progress-bar{background:var(--chapter-surface)}.c4-current progress::-webkit-progress-value{background:var(--chapter-accent)}.c4-pin-states{display:grid;gap:8px}.c4-pin-state{display:flex;align-items:center;justify-content:space-between;gap:5px;padding:10px 8px;background:var(--chapter-deep);border-radius:9px;font-size:12px}.c4-pin-name{font-weight:700;color:var(--cream)}.c4-pin-name small{display:block;font-size:9px;color:var(--chapter-muted);margin-top:3px;font-weight:400}.c4-live-led{display:flex;align-items:center;gap:5px;white-space:nowrap}.c4-live-led i{width:15px;height:15px;border-radius:50%;background:#776351;border:2px solid #a99170;display:inline-block}.c4-live-led i.on{background:#ffd273;border-color:#ffe8a8}.c4-flow-arrow{color:var(--chapter-muted)}.c4-pin-state strong{font-size:10px;color:#ffc1a5;min-width:32px;text-align:center}.c4-pin-state.on strong{color:#c7eba1}.c4-powered-label,.c4-cycle{font-size:11px;color:var(--chapter-muted);margin:12px 0}.c4-cycle{color:var(--cream)}.c4-execution .c4-feedback{margin-bottom:12px}.c4-run{display:grid;grid-template-columns:1fr 1fr;gap:10px;padding:14px;flex-shrink:0}.c4-run .primary,.c4-run .secondary{padding:8px;font-size:13px}.c4-run>.text-button{grid-column:1/-1;border-top:1px solid var(--chapter-border);border-radius:0;padding-top:8px}.c4-reset-note{font-size:10px;text-align:center;color:var(--chapter-muted);padding:0 14px 14px}.c4-pin-dialog{width:min(900px,95vw);max-height:90dvh;border:1px solid var(--chapter-border);border-radius:18px;background:var(--chapter-deep);color:var(--chapter-text);padding:20px}.c4-pin-dialog::backdrop{background:var(--chapter-overlay)}.c4-pin-dialog header{display:flex;align-items:center;justify-content:space-between;gap:12px}.c4-pin-dialog h2{font-size:20px}.c4-pin-dialog p{font-size:13px;line-height:1.6;margin:10px 0;color:var(--chapter-muted)}.c4-pin-dialog>div{overflow:auto;background:#f5e8d2;border-radius:12px}.c4-pin-dialog svg{display:block;width:100%;min-width:620px;height:auto}
@media(max-width:900px){
 .c4-workspace{padding:0 14px}.c4-heading{padding:12px 0;gap:12px}.c4-heading h1{font-size:23px}.c4-heading p{max-width:300px;font-size:12px}.c4-layout{grid-template-columns:1fr;gap:12px}.c4-world-panel{grid-column:1;grid-row:1}.c4-mobile-tabs{grid-column:1;grid-row:2;display:flex;border-radius:12px;background:var(--chapter-deep);padding:4px;border:1px solid var(--chapter-border)}.c4-mobile-tabs button{flex:1;border-radius:9px;font-size:14px;color:var(--chapter-muted)}.c4-mobile-tabs button[aria-selected=true]{background:var(--chapter-surface);color:var(--cream);font-weight:700}.c4-program,.c4-electronics{grid-column:1;grid-row:3}.c4-workspace[data-tab=circuit] .c4-program,.c4-workspace[data-tab=program] .c4-electronics{display:none}.c4-edit-footer{grid-column:1;grid-row:4}.c4-blocks{max-height:310px}.c4-watching .c4-layout{grid-template-columns:1fr}.c4-execution{grid-column:1;grid-row:2}.c4-execution-readings{display:grid;grid-template-columns:1fr 1fr;gap:10px 14px}.c4-current{margin-bottom:0}.c4-pin-states{align-content:center}.c4-powered-label{grid-column:1/-1;margin:0}.c4-cycle{margin:0}.c4-execution .c4-feedback{grid-column:1/-1;margin:0}.c4-run{padding-top:12px}.c4-run>.text-button{grid-column:auto;grid-row:2;grid-column:1/-1}.c4-reset-note{display:none}
}
@media(max-width:550px){
 body[data-mode=chapter4] .topbar{height:54px;padding:5px 12px}.c4-workspace{padding:0 10px}.c4-heading{display:block;padding:12px 2px}.c4-heading h1{font-size:21px;margin-top:4px}.c4-heading .eyebrow{font-size:9px}.c4-heading p{font-size:12px;max-width:none;margin-top:6px;line-height:1.4}.c4-panel-label{padding:8px 12px;min-height:38px;font-size:9px}.c4-panel-label strong{font-size:11px}.c4-road-caption{font-size:10px;padding:8px 10px;gap:6px}.c4-world-panel,.c4-editor-panel,.c4-execution{border-radius:14px}.c4-block-copy{font-size:14px}.c4-blocks{max-height:285px}.c4-component-tray{margin-inline:10px;flex-wrap:wrap}.c4-component-tray .inventory{min-width:210px}.c4-power{display:flex;justify-content:space-between;align-items:center;gap:15px;width:100%;padding:7px 12px}.c4-power strong{margin:0}#c4-circuit{margin-inline:10px}#c4-circuit svg{max-height:none}.c4-wiring{padding:10px;grid-template-columns:1fr}.c4-connection{padding:8px}.c4-guide{font-size:11px}.c4-edit-footer{flex-direction:column;align-items:stretch;padding:10px 12px;gap:7px}.c4-edit-footer>div{justify-content:space-between}.c4-edit-footer .c4-feedback{font-size:12px}.c4-edit-footer .primary{flex:1}.c4-execution-readings{padding:0 10px;grid-template-columns:1fr;gap:10px}.c4-current{padding:10px 12px}.c4-current h2{font-size:19px;margin:5px 0}.c4-current>small{font-size:9px}.c4-current progress{margin:8px 0 5px}.c4-pin-states{grid-template-columns:repeat(2,minmax(0,1fr));gap:6px}.c4-pin-state{flex-wrap:wrap;justify-content:center;gap:5px;padding:8px 5px;font-size:11px}.c4-pin-name{width:100%;display:flex;justify-content:space-between;align-items:center}.c4-pin-name small{margin:0}.c4-pin-state .c4-flow-arrow:first-of-type{display:none}.c4-pin-state strong{min-width:24px;font-size:9px}.c4-powered-label{font-size:10px}.c4-run{padding:10px;gap:7px}.c4-run>.text-button{min-height:44px}.c4-map{margin:24px 10px;padding:24px}
}
@media(max-width:900px) and (max-height:520px) and (orientation:landscape){
 body[data-mode=chapter4] #app{padding-bottom:6px}body[data-mode=chapter4] .topbar{height:44px;padding:0 14px}.c4-workspace{padding:0 10px}.c4-heading{padding:7px 0;display:flex}.c4-heading .eyebrow{display:none}.c4-heading h1{font-size:17px;margin:0}.c4-heading p{display:none}.c4-watching .c4-layout{grid-template-columns:minmax(0,1fr) 264px;gap:10px;align-items:stretch}.c4-watching .c4-world-panel{display:flex;flex-direction:column}.c4-watching #c4-junction{flex:1;display:flex;align-items:center;justify-content:center}.c4-watching #c4-junction>svg{height:calc(100dvh - 154px);width:100%;min-height:190px;object-fit:contain}.c4-watching .c4-road-caption{font-size:9px;padding:6px 9px}.c4-watching .c4-panel-label{min-height:31px;padding:7px 10px;font-size:9px}.c4-watching .c4-execution{grid-column:2;grid-row:1;max-height:calc(100dvh - 88px)}.c4-execution-readings{display:block;padding:0 10px}.c4-current{padding:8px 10px;margin-bottom:8px}.c4-current h2{font-size:17px;margin:4px 0}.c4-current>small{font-size:8px}.c4-current progress{margin:6px 0 4px;height:6px}.c4-current>span{font-size:10px}.c4-pin-states{gap:5px}.c4-pin-state{padding:5px 7px;font-size:11px}.c4-powered-label,.c4-cycle,.c4-reset-note{display:none}.c4-run{padding:8px;gap:4px;background:var(--chapter-panel)}.c4-run .primary,.c4-run .secondary{font-size:12px}.c4-run>.text-button{padding:2px;border:0}.c4-execution .c4-feedback{font-size:11px;margin-top:8px}.c4-editing .c4-layout{grid-template-columns:1fr 1fr}.c4-editing .c4-world-panel{grid-column:1;grid-row:1 / span 2;align-self:start}.c4-editing .c4-mobile-tabs{grid-column:2;grid-row:1}.c4-editing .c4-editor-panel{grid-column:2;grid-row:2}.c4-editing .c4-edit-footer{grid-column:1/-1;grid-row:3}.c4-editing .c4-blocks{max-height:220px}
}
@media(prefers-reduced-motion:reduce){.c4-blocks{scroll-behavior:auto}}
@media(min-width:701px){.home-chapters{grid-template-columns:repeat(3,minmax(0,1fr))}}
/* The same two editing tabs keep the preview and primary action together on desktop. */
@media(min-width:901px){
 .c4-editing .c4-world-panel{grid-column:1;grid-row:1 / span 3}
 .c4-editing .c4-mobile-tabs{display:flex;grid-column:2;grid-row:1;border:1px solid var(--chapter-border);border-radius:12px;background:var(--chapter-deep);padding:4px}
 .c4-mobile-tabs button{flex:1;border-radius:9px;font-size:14px;color:var(--chapter-muted)}
 .c4-mobile-tabs button[aria-selected=true]{background:var(--chapter-surface);color:var(--cream);font-weight:700}
 .c4-editing .c4-editor-panel{grid-column:2;grid-row:2}
 .c4-workspace[data-tab=circuit] .c4-program,.c4-workspace[data-tab=program] .c4-electronics{display:none}
 .c4-editing .c4-edit-footer{grid-column:2;grid-row:3;flex-wrap:wrap;padding:10px 14px}
 .c4-edit-footer>div{width:100%;justify-content:space-between}.c4-edit-footer .primary{flex:1}
 .c4-editing #c4-circuit svg{max-height:320px}.c4-editing .c4-wiring{grid-template-columns:1fr}
}
@media(max-width:900px) and (max-height:520px) and (orientation:landscape){
 .c4-execution .c4-pin-states{grid-template-columns:repeat(2,minmax(0,1fr))}
 .c4-execution .c4-pin-state{flex-wrap:wrap;justify-content:center;gap:3px;padding:6px 4px;font-size:10px}
 .c4-execution .c4-pin-name{width:100%;display:flex;align-items:center;justify-content:space-between}
 .c4-execution .c4-pin-name small{font-size:8px;margin:0}.c4-execution .c4-live-led i{width:12px;height:12px}.c4-execution .c4-pin-state strong{font-size:9px;min-width:21px}
}
.c4-drag-handle{width:44px;min-width:44px;align-self:stretch;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:1px;padding:2px;color:var(--chapter-muted);cursor:grab;touch-action:none;user-select:none;border-radius:6px}.c4-drag-handle>span{font-size:21px;line-height:1}.c4-drag-handle>small{font-size:10px}.c4-drag-handle:active{cursor:grabbing}.c4-drag-source{opacity:.4}.c4-block.c4-drop-before{box-shadow:0 -5px 0 var(--chapter-accent)}.c4-block.c4-drop-after{box-shadow:0 5px 0 var(--chapter-accent)}.c4-drag-ghost{position:fixed;z-index:100;pointer-events:none;padding:12px 18px;white-space:pre-line;border:2px solid var(--chapter-accent);border-radius:12px;background:var(--chapter-surface);color:var(--chapter-text);box-shadow:0 8px 24px var(--chapter-shadow);font-size:14px;line-height:1.5;opacity:.95}