:root{color-scheme:light;--ink:#064575;--blue:#0087f5;--line:#c7e2e7;--mint:#e4f5eb;--cream:#fff8e7}*{box-sizing:border-box}body{margin:0;color:var(--ink);background:linear-gradient(120deg,#edf9ff,#fffcf3);font-family:system-ui,-apple-system,"Meiryo",sans-serif;line-height:1.7}main{max-width:1240px;margin:auto;padding:20px 24px 40px}button,a,input,summary{-webkit-tap-highlight-color:transparent}button{font:inherit;color:var(--ink);background:white;border:1px solid #a1cbd8;border-radius:12px;min-height:44px;padding:8px 15px;cursor:pointer;line-height:1.5}button:hover{background:#edf8ff;border-color:#0087f5}button:disabled{cursor:default;opacity:.6}button:focus-visible,a:focus-visible,input:focus-visible,summary:focus-visible{outline:3px solid #b26200;outline-offset:3px}[tabindex="-1"]:focus{outline:none}[hidden]{display:none!important}h1,h2,p{margin:0}h1{font-size:30px;letter-spacing:.03em;line-height:1.4}h1 span{display:block;font-size:14px;font-weight:500;letter-spacing:.08em;margin-top:5px}h2{font-size:20px;line-height:1.5}small{font-size:12px;font-weight:500}rt{font-size:10px}.intro{display:flex;align-items:center;justify-content:space-between;gap:20px;margin-bottom:18px}.eyebrow{font-size:12px;font-weight:700;letter-spacing:.06em;margin-bottom:4px}.about-link{font-size:13px;white-space:nowrap}.era-tabs{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin-bottom:14px;max-width:600px}.era-tabs button{font-size:20px;font-weight:700;padding:9px}.era-tabs small{margin-left:12px}.era-tabs [aria-pressed="true"]{color:white;background:#087fc6;border-color:#087fc6;box-shadow:0 3px 0 #06629a}.town-card{border:1px solid var(--line);background:#fff;border-radius:24px;overflow:hidden;box-shadow:0 7px 25px #164c6a09}.scene-heading{display:flex;align-items:center;justify-content:space-between;gap:8px;padding:15px 20px 10px}.scene-heading p{font-size:12px}.reset{background:#eff9fe;white-space:nowrap;font-weight:700}.viewport{position:relative;height:440px;background:radial-gradient(ellipse at 45% 25%,#fcfced 0%,#e9f5ec 65%,#d7ebea 100%);isolation:isolate}#scene{width:100%;height:100%}canvas{display:block;width:100%;height:100%;touch-action:none}.scene-label{position:absolute;bottom:13px;left:16px;font-size:11px;background:#ffffffb8;border-radius:20px;padding:3px 12px;pointer-events:none}.loading{position:absolute;inset:0;display:grid;place-content:center;padding:24px;text-align:center;background:#eaf6ed;z-index:2;font-size:16px}.markers{position:absolute;inset:0;pointer-events:none;overflow:hidden}.marker{position:absolute;transform:translate(-50%,-100%);background:#fffdf4ed;border:1px solid #bb9b58;border-radius:50%;width:27px;height:27px;text-align:center;font-size:13px;font-weight:800;line-height:25px;box-shadow:0 2px 3px #0002}.marker.active{background:#fff0a1;border:2px solid #785700}.gesture-help{font-size:12px;text-align:center;padding:8px 12px;background:#f6faf8}.touch-help{display:none}.controls{display:flex;align-items:center;justify-content:center;gap:10px;flex-wrap:wrap;padding:12px}.controls>div{display:flex;gap:5px}.controls button{padding:8px 13px}.roof-control{font-size:13px;display:flex;align-items:center;gap:4px;min-height:44px;cursor:pointer}.roof-control input{width:19px;height:19px;accent-color:#087fc6}.pan-controls{border-top:1px solid #e8f0ef;font-size:12px;padding:0 18px}.pan-controls summary{padding:10px;cursor:pointer;min-height:44px}.section-top,.panel-top{display:flex;justify-content:space-between;align-items:center;gap:10px}.discover{margin:24px 0 14px}.section-top{margin-bottom:12px}#selected-status{font-size:12px}.target-list{display:grid;grid-template-columns:repeat(5,1fr);gap:8px}.target-list button{text-align:left;background:#fffdf8;padding:12px;display:flex;align-items:center;gap:10px}.target-list button[aria-pressed="true"]{border:2px solid #bb8500;background:#fff4be;padding:11px}.target-number{display:grid;place-content:center;width:29px;height:29px;flex-shrink:0;background:#e5f2ed;border-radius:50%;font-weight:700}.target-list strong{font-size:14px;display:block}.target-list small{font-size:11px;display:block}.detail,.quiz-panel{border:1px solid var(--line);border-left:5px solid #299780;border-radius:18px;background:white;padding:22px 26px;margin-top:18px;scroll-margin-top:16px}.panel-top .eyebrow{color:#377c71}.panel-top button{font-size:12px}.detail h2{font-size:24px}#detail-reading{font-size:12px;margin:0 0 12px}#detail-text{max-width:75ch}.look{margin:12px 0;background:#eef7f6;padding:12px 16px;border-radius:10px;font-size:14px}.primary,#next-question{background:#0087f5;color:white;border-color:#0087f5;font-weight:700}.challenge{margin-top:28px;background:#fff9e9;border:1px solid #e8dbb8;border-radius:22px;padding:24px}.challenge p{font-size:14px}.question-list{display:flex;gap:8px;flex-wrap:wrap;margin-top:16px}.question-list button{font-size:13px}.memory-note{font-size:12px!important;margin-top:15px;color:#55728a}.quiz-panel{border-left-color:#1682c8;background:#f9fdff}#quiz-prompt{margin:10px 0;font-size:17px}#quiz-options{display:grid;gap:8px}#quiz-options button{text-align:left;padding:13px 16px}#quiz-feedback{border-radius:12px;background:#e3f3ed;padding:16px;margin:16px 0}#quiz-feedback.incorrect{background:#fff1db}#quiz-feedback strong{display:block;margin-bottom:6px}#find-instruction{background:#e5f3fb;padding:12px;font-size:14px}.about{margin-top:25px;padding:20px;border:1px solid var(--line);border-radius:18px;background:#fff}.about summary{cursor:pointer;font-weight:700;min-height:44px;align-content:center}.about p{margin:12px 0;font-size:14px}.about ul{padding-left:20px;font-size:13px}.about a{overflow-wrap:anywhere}footer{display:flex;justify-content:center;gap:24px;font-size:13px;margin-top:28px}a{color:#086fae}.viewport.list-view{height:150px}.viewport.list-view .scene-label{display:none}
@media(max-width:900px){.target-list{grid-template-columns:repeat(3,1fr)}.viewport{height:400px}.controls{gap:7px}.intro{align-items:flex-start}.era-tabs{max-width:none}}
@media(max-width:540px){main{padding:14px 12px 30px}h1{font-size:27px}h1 span{font-size:12px}.intro{gap:5px;flex-wrap:wrap;margin-bottom:12px}.about-link{font-size:12px}.eyebrow{font-size:11px}.era-tabs{gap:7px}.era-tabs button{font-size:18px}.era-tabs small{display:block;margin-left:0;font-size:11px}.scene-heading{padding:12px;align-items:flex-start}.scene-heading h2{font-size:18px}.scene-heading p{font-size:10px;max-width:210px}.reset{font-size:12px;padding:8px}.viewport{height:340px}.desktop-help{display:none}.touch-help{display:inline}.gesture-help{font-size:11px}.gesture-help>span:last-child{display:block}.controls{padding:10px 7px;gap:5px}.controls button{padding:8px 10px;font-size:12px}.roof-control{font-size:12px}.target-list{grid-template-columns:1fr 1fr}.target-list button{padding:10px;gap:7px}.target-list button[aria-pressed="true"]{padding:9px}.target-list strong{font-size:13px}.target-list small{font-size:10px}.section-top{flex-wrap:wrap}h2{font-size:19px}h2 small{display:block}.detail,.quiz-panel{padding:16px;margin-top:14px}.detail h2{font-size:22px}.detail p{font-size:14px}.look{padding:10px}.challenge{padding:18px}.question-list button{flex:1 1 42%;padding:10px 8px}.about{padding:14px}.marker{width:24px;height:24px;line-height:22px;font-size:12px}#quiz-prompt{font-size:16px}footer{gap:14px;font-size:12px}}
.skip-link{position:absolute;left:12px;top:-100px;z-index:1000;background:white;padding:8px 14px;border:2px solid #0087f5;border-radius:8px}.skip-link:focus{top:8px}.scene-task{padding:10px 18px;background:#fff1c7;font-size:14px;border-top:1px solid #e7d490}
.marker.active{width:auto;height:auto;min-height:27px;padding:0 8px;border-radius:14px;white-space:nowrap;color:#fff;background:#0068b5;border:2px solid #fff;box-shadow:0 1px 5px #06457566}
.target-list button[aria-pressed="true"]{border-color:#0068b5;background:#e4f5ff}
/* A non-modal explanation card leaves the model interactive and the page still. */
.detail{position:fixed;z-index:50;right:max(16px,calc((100vw - 1240px)/2));bottom:16px;width:350px;max-width:calc(100vw - 32px);max-height:calc(100dvh - 96px);margin:0;padding:16px;border:2px solid #399acb;border-radius:18px;box-shadow:0 8px 30px #174a7038;display:flex;flex-direction:column;overflow:hidden}
.detail .panel-top{flex-shrink:0;align-items:flex-start;gap:12px;margin-bottom:8px}.detail h2{font-size:21px}.detail #detail-reading{margin:2px 0 0;font-size:11px}.detail #close-detail{flex-shrink:0;min-height:44px;padding:8px 10px;font-size:12px}.detail-body{min-height:0;overflow-y:auto;overscroll-behavior:contain;padding:3px}.detail #detail-text{font-size:14px;line-height:1.75}.detail-actions{display:flex;flex-wrap:wrap;gap:6px;margin-top:12px}.detail-actions button{font-size:12px;padding:8px 10px;flex:1 1 auto}.detail .look{margin:10px 0 0;padding:10px;font-size:13px}
@media(max-width:600px){.detail{left:8px;right:8px;bottom:max(8px,env(safe-area-inset-bottom));width:auto;max-width:none;max-height:42dvh;padding:12px;border-radius:16px}.detail h2{font-size:19px}.detail .panel-top{margin-bottom:4px}.detail #detail-text{font-size:14px;line-height:1.65}.detail-actions{margin-top:8px}}
/* Observation and quiz are separate screens; one shared model moves between them. */
.activity-nav{display:grid;grid-template-columns:1fr 1fr;gap:6px;padding:6px;margin:0 0 18px;background:#fff;border:1px solid var(--line);border-radius:17px;position:sticky;top:8px;z-index:20;box-shadow:0 3px 14px #1547710b}
.activity-nav button{font-weight:700;border-color:transparent;background:transparent}.activity-nav [aria-current="page"]{background:#087fc6;color:#fff;border-color:#087fc6}.screen-guide{font-size:14px;margin-bottom:14px}.screen-guide,h2[tabindex="-1"],#quiz-panel,#quiz-menu{scroll-margin-top:84px}
.quiz-invitation{display:flex;align-items:center;justify-content:space-between;gap:12px;background:#fff9e9;border-radius:18px;padding:18px;margin-top:20px}.quiz-invitation p{font-size:14px}.quiz-menu,.quiz-finish{background:white;border:1px solid var(--line);border-radius:22px;padding:28px}.quiz-menu>p,.quiz-finish>p{margin:8px 0 0}.quiz-menu h2,.quiz-finish h2{font-size:25px}.course-list{display:grid;grid-template-columns:repeat(3,1fr);gap:14px;margin-top:24px}.course-list button{position:relative;text-align:left;display:flex;flex-direction:column;align-items:flex-start;gap:8px;padding:24px 20px;background:#f1faff;border:2px solid #b9deed}.course-list button:nth-child(2){background:#f0f9ee}.course-list button:nth-child(3){background:#fffaea}.course-list strong{font-size:21px;margin-top:8px}.course-list small{font-size:14px}.course-number{font-size:12px;font-weight:700;padding:3px 10px;border-radius:20px;background:#fff}.course-start{margin-top:10px;font-weight:700;color:#006db1}.quiz-finish>div{display:flex;flex-wrap:wrap;gap:10px;margin-top:22px}
#quiz-screen .quiz-panel{margin-top:0;padding:24px;border:1px solid var(--line);border-radius:22px;background:white}#quiz-screen .panel-top{margin-bottom:18px}#quiz-kind{font-size:14px;text-align:right}#quiz-heading{font-size:25px}#quiz-prompt{font-weight:600;font-size:19px;margin:12px 0 20px;max-width:65ch}.answer-guide{padding:10px 14px;background:#eef8ff;border-radius:10px;font-size:14px;margin:0 0 14px}#inspect-model{margin-bottom:18px;font-size:14px}.quiz-workspace.has-model{display:grid;grid-template-columns:minmax(0,1.2fr) minmax(0,1fr);gap:22px;align-items:start}.quiz-answer-area{min-width:0}#quiz-options button{font-size:17px;min-height:56px}#quiz-options small{display:block;font-size:11px}#quiz-options.find-options{grid-template-columns:1fr 1fr}#quiz-options.find-options button{font-size:15px;padding:10px}#quiz-feedback{margin:14px 0;font-size:15px}#quiz-feedback p{margin:0}#next-question{width:100%;min-height:50px}.compare-eras{display:flex;gap:8px;margin-bottom:12px}.compare-eras button{flex:1;font-size:14px}.compare-eras [aria-pressed="true"]{background:#087fc6;color:white}
#quiz-model-area .town-card{border-radius:16px}#quiz-model-area .scene-heading{padding:8px 12px;align-items:center}#quiz-model-area .scene-heading h2{font-size:15px}#quiz-model-area .scene-heading p{display:none}#quiz-model-area .reset{font-size:12px}#quiz-model-area .viewport{height:300px}#quiz-model-area .gesture-help{display:none}#quiz-model-area .pan-controls{display:none}#quiz-model-area .controls{gap:6px;padding:7px}#quiz-model-area .controls>div:nth-child(3){display:none}#quiz-model-area .roof-control{font-size:12px}#quiz-model-area .viewport.list-view{height:120px}
@media(max-width:900px){.quiz-workspace.has-model{grid-template-columns:1fr}.course-list{gap:10px}.course-list button{padding:18px 14px}.course-list strong{font-size:18px}}
@media(max-width:540px){.activity-nav{top:8px;margin-bottom:14px;padding:4px}.activity-nav button{padding:10px 6px;font-size:15px}.screen-guide{font-size:13px}.quiz-menu,.quiz-finish,#quiz-screen .quiz-panel{padding:18px 14px}.quiz-menu h2,.quiz-finish h2,#quiz-heading{font-size:22px}.quiz-menu>p,.quiz-finish>p{font-size:14px}.course-list{grid-template-columns:1fr;gap:12px;margin-top:20px}.course-list button{padding:15px 18px;gap:3px}.course-list strong{margin:0;font-size:21px}.course-number{position:absolute;right:15px;top:14px}.course-start{margin-top:7px;font-size:14px}.course-list small{font-size:13px}.quiz-invitation{flex-direction:column;align-items:stretch;text-align:center}.quiz-finish>div{flex-direction:column}#quiz-screen .panel-top{gap:8px;margin-bottom:14px;align-items:flex-start}#quiz-kind{font-size:12px}#quiz-prompt{font-size:17px;margin:10px 0 16px}.answer-guide{font-size:13px}#quiz-model-area .viewport{height:240px}#quiz-model-area .scene-heading h2{font-size:13px}#quiz-model-area .scene-heading{padding:7px 9px}.quiz-workspace.has-model{gap:14px}#quiz-options button{font-size:16px}#quiz-options.find-options button{font-size:14px;padding:9px}#quiz-feedback{padding:13px;font-size:14px}.quiz-finish .primary{width:100%}}
@media(prefers-reduced-motion:reduce){*,*::before,*::after{scroll-behavior:auto!important;animation:none!important;transition:none!important}}

/* Keep the next action in reach while leaving explanations and observations scrollable. */
@media(max-width:700px),(max-height:500px) and (max-width:1000px){
  #quiz-panel:has(#next-question:not([hidden])){padding-bottom:calc(84px + env(safe-area-inset-bottom,0px))}
  #quiz-panel :is(#next-question:not([hidden])){position:fixed;z-index:20;left:max(12px,env(safe-area-inset-left,0px));right:max(12px,env(safe-area-inset-right,0px));bottom:calc(10px + env(safe-area-inset-bottom,0px));width:auto;margin:0;min-height:52px;box-shadow:0 0 0 6px #fffdf7,0 -4px 18px #073e7d24}
}