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:root{color-scheme:light;--paper:#fff;--bg:#f3f5f8;--ink:#202d40;--muted:#606d7d;--line:#dce2e9;--blue:#254a75;--accent:#b9473d;--soft:#edf2f8;--mint:#007a75;--orange:#946019;--rose:#c67578;--sans:'DM Sans','Noto Sans KR',sans-serif;--serif:'Noto Serif KR',Georgia,serif;font-family:var(--sans);font-size:16px;color:var(--ink);background:var(--bg)}
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/* Masthead and table of contents. */
.topbar{height:78px;padding:0 34px;background:#fff;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;gap:20px}.brand{display:flex;align-items:center;gap:13px;text-decoration:none;color:var(--ink)}.brand-mark{display:flex;align-items:center;justify-content:center;width:37px;height:37px;border:1px solid var(--accent);color:var(--accent);font:600 27px Georgia,serif;letter-spacing:-2px;padding-right:3px}.brand-mark span{display:none}.brand>span:last-child{font:700 19px var(--sans);letter-spacing:3px}.brand-sub{display:block;font:500 11px var(--sans);letter-spacing:1.5px;margin-top:3px;color:var(--muted)}.top-actions{display:flex;align-items:center;gap:26px}.edition{color:var(--muted);font-size:.75rem;letter-spacing:1.4px}.language-label{display:flex;align-items:center;gap:8px;font-size:.75rem;color:var(--muted)}.language-label select{border:0;background:transparent}.app-layout{max-width:1640px;margin:auto;display:grid;grid-template-columns:238px minmax(0,1fr);align-items:start}.library{position:sticky;top:0;height:calc(100dvh - 12px);max-height:1100px;border-right:1px solid var(--line);background:#f8fafc;padding:30px 18px;display:flex;flex-direction:column;min-height:0}.library-heading{display:flex;justify-content:space-between;align-items:center;font-size:.8125rem;font-weight:600;letter-spacing:.3px}.library-heading>span:last-child{font:500 .8125rem var(--sans);color:var(--muted)}.search-label input{width:100%;padding:11px 12px;border:1px solid #cfd7e2;background:#fff;border-radius:4px;margin:19px 0 8px;color:var(--ink);font-size:.875rem;min-height:44px}.search-label input::placeholder{color:#747f8e}#rhythm-list{overflow-y:auto;min-height:0;padding:0 3px 20px 0;scrollbar-width:thin;scrollbar-color:#b6c2cf transparent}.group-heading{font-size:.75rem;font-weight:600;color:#6f7b8b;margin:24px 10px 8px;letter-spacing:.5px}.rhythm-button{width:100%;display:block;text-align:left;border:0;border-left:3px solid transparent;border-radius:0;background:transparent;padding:9px 10px;min-height:44px;font-size:.875rem;line-height:1.45;margin:1px 0}.rhythm-button:hover{background:#edf1f6}.rhythm-button[aria-current=true]{border-left-color:var(--accent);background:#e9eff7;color:#183e6a;font-weight:600}.short-name{display:block;font-size:.75rem;font-weight:400;color:var(--muted);margin-top:2px}.library-note{margin:16px 9px 0;padding-top:15px;border-top:1px solid var(--line);color:var(--muted);font-size:.8125rem;line-height:1.8}.library-note p{margin:0;white-space:pre-line}.note-rule{display:none}.empty-search{font-size:.875rem;color:var(--muted)}main{min-width:0;padding:28px 36px 36px;background:#fff;min-height:calc(100dvh - 78px)}

/* Navigation reads as chapters rather than dashboard cards. */
.workspace-navigation{margin-bottom:25px}.workspace-tabs{display:flex;gap:28px;border-bottom:1px solid var(--line)}.workspace-tabs button{padding:12px 2px 14px;border:0;border-bottom:3px solid transparent;border-radius:0;background:none;color:var(--muted);font-size:.9375rem;font-weight:500;white-space:nowrap}.workspace-tabs button:hover{color:var(--ink);background:none}.workspace-tabs button[aria-pressed=true]{border-bottom-color:var(--accent);color:var(--ink);font-weight:700}.mobile-rhythm{display:none}.title-row{display:flex;justify-content:space-between;align-items:center;gap:24px;margin:0 0 22px}.eyebrow{font-size:.75rem;font-weight:600;color:var(--accent);letter-spacing:1.4px;text-transform:uppercase;margin-bottom:10px}h1{font:600 clamp(1.75rem,2.5vw,2.75rem)/1.4 var(--serif);letter-spacing:-1px;margin:0;color:#17283f}#rhythm-subtitle{margin:8px 0 0;font-size:.9375rem;color:var(--muted)}.rate-readout{border-left:1px solid var(--line);padding-left:22px;flex-shrink:0;min-width:92px}.rate-readout>span{font-size:.75rem;color:var(--muted)}.rate-readout>div{display:flex;align-items:baseline;gap:6px;margin-top:4px}.rate-readout strong{font-size:2.25rem;line-height:1.15;font-weight:500;color:#23405f;font-variant-numeric:tabular-nums}.rate-readout div>span{font-size:.8125rem;color:var(--muted)}.case-bar{display:flex;flex-wrap:wrap;align-items:start;gap:12px 20px;padding:0 0 18px}.case-bar>#variant-wrap{display:flex;align-items:center;gap:10px;flex:1;min-width:240px;font-size:.875rem;color:var(--muted)}#variant-wrap select{min-width:0;flex:1}.view-settings{min-width:230px;margin-left:auto}.view-settings>summary{display:flex;align-items:center;gap:12px;min-height:44px;color:var(--blue);font-size:.875rem;list-style:none;padding:10px 0;cursor:pointer}.view-settings>summary::-webkit-details-marker{display:none}.view-settings>summary:after{content:'＋';font-size:1rem;color:var(--blue)}.view-settings[open]>summary:after{content:'−'}#view-settings-value{margin-left:auto;color:var(--muted);font-size:.8125rem;white-space:nowrap}.view-settings[open]{flex-basis:100%;border-top:1px solid var(--line)}.view-settings-body{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px 24px;padding:17px 20px;background:#f4f7fa;border-top:1px solid var(--line);border-bottom:1px solid var(--line)}.view-settings-body>label,.speed-label{display:flex;align-items:center;gap:10px;font-size:.875rem}.heart-legend{display:flex;gap:16px;flex-wrap:wrap;grid-column:1/-1}.heart-legend label{display:flex;gap:7px;align-items:center;font-size:.875rem;min-height:36px}.swatch{width:7px;height:7px;border-radius:50%}.mint{background:#007a75}.rose{background:#c67578}.time-slider{display:grid;grid-template-columns:auto 1fr auto;align-items:center;gap:12px;grid-column:1/-1;min-width:0;font-size:.875rem;color:var(--muted)}.time-slider input{width:100%;min-width:0}.time-slider span{white-space:nowrap}.anatomy-glossary,.reading-hint{grid-column:1/-1;color:var(--muted);font-size:.875rem;line-height:1.85;margin:0}.anatomy-glossary summary{color:var(--blue);min-height:32px}.anatomy-glossary p{margin:8px 0 0}.reading-hint{padding-top:12px;border-top:1px solid var(--line)}

/* Playback stays within reach and uses one clear primary action. */
.learning-bar{display:flex;gap:22px;align-items:center;padding:0 0 0 12px;border-top:1px solid var(--line);background:#f7f9fc}.learning-bar button{border:0;border-radius:0;border-bottom:2px solid transparent;min-height:41px;padding:10px 2px 8px;background:none;color:var(--muted);font-size:.8125rem}.learning-bar button[aria-pressed=true]{border-bottom-color:var(--blue);color:var(--blue);font-weight:600}.transport{display:flex;align-items:center;gap:12px;flex-wrap:wrap}.control-dock{position:sticky;top:0;z-index:20;background:#f7f9fc;border-bottom:1px solid #cbd5e1;padding:11px 12px;margin:0 0 25px;box-shadow:0 4px 6px #1f344008}.reading-controls{flex:1}.reading-buttons,.play-group{display:flex;gap:8px;align-items:center}.reading-buttons button,.play-group button{min-height:44px}.reading-buttons .primary-action,.play-button{background:var(--blue);border-color:var(--blue);color:#fff;font-weight:600;min-width:150px}.reading-buttons .primary-action:hover,.play-button:hover{background:#183954}.play-button{display:flex;align-items:center;justify-content:center;gap:9px}.play-group{flex:1}.icon-button{font-size:1.15rem;min-width:42px;padding:6px 10px}.playback-state{margin-left:auto;font-size:.8125rem;color:var(--muted);white-space:nowrap}.playback-state.is-playing{color:#00645d}.secondary-button{background:white}

/* Anatomy is an open textbook figure; ECG is the only dark instrument surface. */
.study-layout{display:grid;grid-template-columns:minmax(270px,.9fr) minmax(0,1.1fr);grid-template-areas:'heart ecg' 'explanation explanation';gap:28px 26px;align-items:start}.visual-grid{display:contents}.heart-pane{grid-area:heart;min-width:0;display:flex;flex-direction:column;background:#f5f8fc;border-top:2px solid #b7c8dc;padding:17px 14px 0}.pane-top{display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:7px;font-size:.75rem;font-weight:500;color:var(--muted);letter-spacing:.4px}.heart-pane .pane-top{padding:0 4px}.model-label{font-size:.75rem;font-weight:400}.heart-stage{position:relative;height:326px;min-height:240px}.heart-stage canvas{display:block;width:100%;height:100%}.orientation{position:absolute;left:0;bottom:24px;writing-mode:vertical-rl;font-size:.75rem;color:#697a8d;letter-spacing:.5px}.scene-bar{order:3;display:flex;gap:13px;align-items:center;border-top:1px solid #d5dfeb;padding:14px 2px;margin:0}.scene-bar>div{min-width:0}.scene-bar button{min-width:90px;flex-shrink:0;font-size:.8125rem;border-color:#bccadc;background:#fff;color:var(--blue);padding:9px 11px}.focus-key{display:none}#focus-instruction{font-size:.875rem;line-height:1.8;margin:0;color:#4b5c70}.ecg-pane{grid-area:ecg;min-width:0;overflow:hidden;background:#102330;color:#eef5f6;border-radius:5px;border:1px solid #102330}.ecg-pane>.pane-top{padding:17px 16px 12px;color:#c0ced6}.ecg-meta{display:flex;align-items:center;gap:12px;flex-wrap:wrap;font-size:.75rem}.ecg-meta>span:first-child{color:#a7ead9;font-weight:600;letter-spacing:.8px}.ecg-time{font-variant-numeric:tabular-nums;color:#eef5f6}.ecg-wrap{height:205px}.ecg-wrap,.atrial-scroll{overflow-x:auto;overflow-y:hidden;max-width:100%;touch-action:pan-x pan-y;overscroll-behavior-x:contain;scrollbar-width:thin;scrollbar-color:#7c999e #203947;-webkit-overflow-scrolling:touch}.ecg-wrap canvas{display:block;width:100%;height:calc(100% - 12px);max-width:none;touch-action:pan-x pan-y;cursor:grab;user-select:none;-webkit-user-select:none}.ecg-wrap canvas:active,.atrial-scroll canvas:active{cursor:grabbing}.ecg-wrap::-webkit-scrollbar,.atrial-scroll::-webkit-scrollbar{height:10px}.ecg-wrap::-webkit-scrollbar-track,.atrial-scroll::-webkit-scrollbar-track{background:#203947}.ecg-wrap::-webkit-scrollbar-thumb,.atrial-scroll::-webkit-scrollbar-thumb{background:#7c999e;border:2px solid #203947;border-radius:5px}.strip-navigation{display:flex;align-items:start;gap:10px;padding:8px 14px 0}.strip-range-details{flex:1;min-width:0}.strip-range-details>summary{display:flex;align-items:center;gap:8px;min-height:40px;color:#c1d0d9;font-size:.8125rem;cursor:pointer}.strip-range-details>summary:before{content:'↔';color:#a7ead9}#strip-window{font-variant-numeric:tabular-nums;font-size:.75rem;white-space:nowrap}#strip-position{display:block;width:100%;min-height:32px;accent-color:#a7ead9}#strip-return{background:transparent;border-color:#526b7b;color:#e1eaef;margin:0;min-height:40px;padding:8px 10px;font-size:.75rem;flex-shrink:0}#strip-return:hover{background:#28404f}.phase-track{display:grid;grid-template-columns:repeat(4,1fr);gap:6px;margin:10px 14px 0}.phase-track button{font:500 .9375rem var(--sans);min-height:42px;background:#1d3544;border:1px solid #415b6c;color:#d1dde5;border-radius:3px;padding:8px}.phase-track button.active{background:#dcebf3;color:#173950;border-color:#dcebf3}.phase-track button:disabled{opacity:.35}.ecg-bottom{display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:5px;padding:10px 14px 14px}.check-label{display:flex;align-items:center;gap:7px;min-height:36px;font-size:.875rem}.ecg-bottom .check-label{color:#d3e0e7;font-size:.8125rem}.ecg-pane input[type=checkbox]{accent-color:#8ed2c0}.hint{font-size:.75rem;line-height:1.7;color:#a2b7c5}.atrial-view{border-top:1px solid #345060}.atrial-label{font-size:.75rem;color:#e6b977;padding:10px 16px 2px;line-height:1.6}.atrial-scroll{height:87px}.atrial-scroll canvas{display:block;width:100%;height:75px;max-width:none;cursor:grab;touch-action:pan-x pan-y;user-select:none;-webkit-user-select:none}

/* An annotated reading passage, not another dashboard card. */
.explanation{grid-area:explanation;min-width:0;position:relative;padding:23px 0 0;border-top:1px solid #bfcbd8}.explanation>.pane-top{display:none}.phase-head{display:flex;align-items:center;gap:20px}.phase-head>span{font:500 3.3rem/1 Georgia,serif;color:var(--accent);min-width:68px;text-align:left;letter-spacing:-2px}.tiny{display:block;font-size:.75rem;letter-spacing:1px;color:var(--muted);margin:0 0 5px}.phase-head h2{font-size:1.25rem;font-weight:600;line-height:1.5}.phase-description{max-width:76ch;margin:14px 0 22px 88px;font-size:1rem;line-height:1.95;color:#35445a;min-height:0}.deeper-explanation{margin-left:88px;border-top:1px solid var(--line);padding-top:12px;font-size:1rem;line-height:1.85}.deeper-explanation>summary{min-height:38px;cursor:pointer;color:var(--blue);font-size:.875rem}.deeper-explanation p{max-width:80ch;margin:8px 0 16px;color:#4c5c6f;line-height:1.9}.deeper-explanation h3{font-size:1rem;color:#283d57}.notice{padding:0;margin:19px 0;color:var(--muted);font-size:.9375rem;line-height:1.85}.notice summary{font-size:.875rem;color:#8b4b34;cursor:pointer}.notice p{margin:10px 0}.explain-rule{height:1px;background:var(--line)}

/* Courses and teaching tools share the same editorial hierarchy. */
.learning-card{padding:20px 22px;background:#f2f5f9;border-left:3px solid var(--blue);margin-top:20px}.learning-card p{font-size:1rem;line-height:1.9;max-width:85ch}.learning-card h2{font-size:1.25rem;margin:18px 0 8px}.lesson-top,.lesson-nav,.teaching-actions,.loop-controls,.comparison-toolbar,.comparison-transport{display:flex;align-items:center;gap:12px;flex-wrap:wrap}.lesson-top{justify-content:space-between}.lesson-top>span{font-size:.8125rem;color:var(--accent);font-weight:600;font-variant-numeric:tabular-nums}.lesson-top select{max-width:100%;min-width:0}.lesson-nav{margin:18px 0;justify-content:space-between}.lesson-nav button{flex:1;max-width:260px}.learning-card details{margin-top:17px}.learning-card summary{font-size:.875rem;color:var(--blue);cursor:pointer}.learning-card details>p{font-size:.9375rem}#intro-panel{margin:0 0 26px;padding:0 0 22px;background:none;border:0;border-bottom:1px solid var(--line)}#intro-panel h2{font-family:var(--serif);font-size:1.5rem;line-height:1.65}#intro-panel>p{max-width:80ch}#knowledge-check{padding-top:15px;border-top:1px solid var(--line)}#teach-panel{margin-top:18px}#teach-panel>p{margin:0 0 12px}.teaching-actions{margin:15px 0}.teaching-actions label,.teaching-settings>label{display:inline-flex;align-items:center;gap:8px;font-size:.875rem;margin-right:14px}.teaching-settings>label{margin-top:14px}.teaching-actions button:first-child{background:var(--blue);border-color:var(--blue);color:#fff}.prediction{color:#674b31;font-size:.9375rem!important}.loop-controls{border-top:1px solid var(--line);margin:15px 0;padding-top:15px}.loop-controls label{display:flex;gap:8px;align-items:center;flex-wrap:wrap;font-size:.875rem}.loop-controls input{width:88px;border:1px solid #bbc9d8;background:#fff;border-radius:3px;padding:9px;color:var(--ink);min-height:44px}#loop-error{color:#aa322a;font-size:.875rem}.comparison-toolbar{margin:20px 0 14px}.comparison-toolbar label{display:flex;align-items:center;gap:10px;font-size:.875rem;min-width:0}.comparison-toolbar>label:first-child{flex:1}.comparison-toolbar select{min-width:0;max-width:100%}#comparison-panel>.reading-hint{padding:0;border:0;font-size:.875rem;margin-bottom:16px}.comparison-transport{position:sticky;top:0;z-index:20;background:#f2f5f9;border-bottom:1px solid #bdcbdb;padding:12px;margin:0 0 12px}.comparison-transport>input{flex:1;min-width:90px}.comparison-transport>span{font-size:.8125rem;font-variant-numeric:tabular-nums}.comparison-transport>label{display:flex;gap:8px;align-items:center;font-size:.8125rem}#comparison-play{background:var(--blue);border-color:var(--blue);color:#fff}.compare-detail-toggle{margin:10px 0 18px}.comparison-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:22px}.comparison-card{border-top:2px solid #b7c8dc;min-width:0;background:#f5f8fc;padding-top:15px;overflow:hidden}.comparison-case-label{font:600 .8125rem var(--sans);color:var(--accent);display:block;margin:0 15px 9px}.comparison-card>select{width:calc(100% - 30px);margin:0 15px 12px}.compare-heart{width:100%;height:290px;display:block}.compare-ecg{width:100%;height:182px;display:block;background:#0d1b23}.compare-atrial{width:100%;height:75px;display:block;background:#0d1b23}.comparison-card>p{padding:0 17px;margin:17px 0;color:#4b5c70;line-height:1.85;font-size:1rem}.waveforms-first .compare-heart,.waveforms-first .comparison-card>p{display:none}.comparison-why{border-left:3px solid var(--accent);background:#f7f8fa;padding:14px 20px;margin:20px 0;line-height:1.9;font-size:1rem;color:#34465e}

footer{border-top:1px solid var(--line);margin-top:32px;padding-top:20px;color:var(--muted);font-size:.75rem;line-height:1.85}footer>p{margin:0 0 8px;max-width:105ch}footer details{max-width:95ch}footer summary{cursor:pointer;color:var(--blue)}footer ul{padding-left:20px}footer a{color:var(--blue)}.footer-brand{display:block;margin-top:20px;font-size:.6875rem;letter-spacing:1.8px;color:#728095}.teaching-view .library,.large-workspace .library,[data-workspace=compare] .library{display:none}.teaching-view .app-layout,.large-workspace .app-layout,[data-workspace=compare] .app-layout{grid-template-columns:minmax(0,1fr);max-width:1400px}.teaching-view .mobile-rhythm{display:flex;align-items:center;gap:12px;margin-bottom:20px;font-size:.875rem}.teaching-view .mobile-rhythm select{flex:1;min-width:0}.large-workspace .heart-stage{height:420px}.large-workspace .ecg-wrap{height:280px}.large-workspace .phase-description{font-size:1.125rem}.answer-hidden .mobile-rhythm,.answer-hidden .case-bar,.answer-hidden .heart-pane,.answer-hidden .explanation,.answer-hidden .ecg-bottom,.answer-hidden .atrial-view,.answer-hidden .rate-readout,.answer-hidden .learning-bar,.answer-hidden footer,.answer-hidden #phase-track,.answer-hidden #reading-controls,.answer-hidden .playback-state{display:none!important}.answer-hidden .study-layout{display:block}.answer-hidden #play-group{display:flex!important}.answer-hidden #next{display:none}.answer-hidden #related-case{visibility:hidden}.answer-hidden .ecg-wrap{height:320px}.answer-hidden .title-row h1{font-family:var(--sans);font-size:1.5rem}

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