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#183b2920}.paper-building{position:absolute;z-index:2;bottom:85px;left:28%;width:145px;height:155px;background:linear-gradient(90deg,#214b40 50%,#356353 50%);transform:rotate(-4deg);box-shadow:18px 14px 0 #153c2920;transition:transform .6s}.paper-building:before{content:"";position:absolute;inset:-50px -18px auto;height:60px;background:#c39755;clip-path:polygon(50% 0,100% 100%,0 100%)}.paper-building:after{content:"";position:absolute;bottom:0;left:24px;width:30px;height:50px;background:#eedcb1;box-shadow:65px -50px 0 -5px #eedcb1}.paper-building span{position:absolute;top:25px;left:24px;color:#f1deb1;font:italic 40px Georgia}.paper-stage:hover .paper-building{transform:rotate(2deg) translateY(-7px)}.scene-caption{position:absolute;bottom:0;left:0;right:0;text-align:center;letter-spacing:.16em;font-size:.65rem!important}.scene-festival .paper-building{width:185px;left:20%;height:115px;background:repeating-linear-gradient(90deg,#bd8b54 0 25px,#efe0b4 25px 50px)}.scene-festival 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button{cursor:pointer;border:1px solid #315e4c;padding:13px 16px;border-radius:4px}.design-toggle{background:#dfc58a;color:#163e32}.design-toggle[aria-pressed=true]{background:#285947;color:white}.experiment-controls label{font-size:.8rem;font-weight:700}.experiment-controls select{width:100%;padding:13px 10px;background:#fffcf3;color:#234b3e;border:1px solid #738673;border-radius:4px}.run-experiment{background:#204d40;color:#fff}.reset-experiment{background:transparent;color:#244d3e;margin:8px}.experiment-stage{position:relative;display:flex;gap:8px;align-items:center;justify-content:center;min-height:250px;perspective:900px;border-bottom:2px solid #b7bfa2;background:radial-gradient(ellipse at bottom,#a8b59850,transparent 65%)}.paper-piece{position:relative;flex:1;min-width:0;min-height:140px;background:#335a4b;color:#f5eddb;padding:18px 10px;transform:rotateY(-12deg) rotateZ(-3deg);box-shadow:6px 8px 0 #19372b20;transition:transform .65s,background 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translateX(8px)}to{opacity:1;transform:none}}@media(max-width:800px){.solid-index a{justify-content:center;padding:9px}.solid-index span{display:none}.book-toolbar{display:block}.book-toolbar>span{display:none}.book-tabs button{padding:13px 10px;font-size:.82rem;flex:1}.book-tabs{width:100%}.book-spread{grid-template-columns:1fr;min-height:0}.book-leaf+.book-leaf{border-left:0;border-top:1px solid #c4c6b1;background:linear-gradient(#233a2710,transparent 20px)}.book-leaf{background:none}.paper-stage{height:310px}.lesson-heading{padding-top:28px}.lesson-heading h1{max-width:95%}.book-pagination button{font-size:.72rem;padding:12px}.page-count{font-size:.65rem;text-align:center}.lesson-navigation{font-size:.85rem}.experiment-stage{min-height:225px}.book-shell{width:calc(100% - 24px)}.book-leaf h2{font-size:2.5rem}}@media(prefers-reduced-motion:reduce){.solid-world *, .solid-world *:before,.solid-world *:after{animation:none!important;transition:none!important}}
.book-toolbar{flex-wrap:wrap}.book-tabs{flex-wrap:wrap}.book-tabs button{padding:13px 14px}@media(max-width:800px){.book-tabs{display:grid;grid-template-columns:repeat(3,1fr);gap:4px}.book-tabs button{border-bottom:1px solid #5d7867;padding:12px 8px;border-radius:5px 5px 0 0;font-size:.78rem}}
.scene-robot .paper-building{width:130px;height:145px;left:32%;bottom:72px;border-radius:18px 18px 10px 10px;background:linear-gradient(90deg,#285548 50%,#447762 50%);border:3px solid #193e35;box-shadow:12px 12px 0 #153c2920}.scene-robot .paper-building:before{clip-path:none;inset:-65px -10px auto;height:60px;border-radius:14px;background:radial-gradient(circle at 28% 45%,#eacf89 0 8px,transparent 9px),radial-gradient(circle at 72% 45%,#eacf89 0 8px,transparent 9px),#204638;border:3px solid #7d9e7e}.scene-robot .paper-building:after{left:14px;bottom:-22px;width:28px;height:35px;background:#142e2b;border-radius:7px;box-shadow:68px 0 0 #142e2b}.scene-robot .paper-building span{left:40px;top:32px;border:1px solid #96b69c;border-radius:50%;width:44px;height:44px;line-height:44px;text-align:center;font-size:27px}.scene-robot .paper-sun{width:70px;height:70px;right:18px;top:10px;background:#ddc98e40;box-shadow:none;border:1px dashed #9baa87}

.solid-world{position:relative;isolation:isolate;overflow:hidden;background:radial-gradient(ellipse at 88% 12%,#315e48 0,transparent 45%),linear-gradient(145deg,#091e23,#16392f 55%,#071c20)}.solid-world>.container{position:relative;z-index:1}.solid-atmosphere{position:absolute;inset:0;z-index:0;pointer-events:none;overflow:hidden;mask-image:linear-gradient(#000a,#000 30%,#0005)}.solid-atmosphere:before{content:"";position:absolute;inset:-100px -30%;background:radial-gradient(ellipse at 75% 20%,#c5a96522,transparent 35%),repeating-radial-gradient(ellipse at 80% 5%,transparent 0 95px,#9cc29b12 96px 97px,transparent 98px 180px);transform:rotate(-14deg)}.solid-atmosphere svg{width:100%;height:calc(100% + 300px);min-height:1600px;transform:translateY(var(--circuit-travel,0px));margin-top:-100px;fill:none}.circuit-rail{stroke:#9dbe9840;stroke-width:1}.circuit-signal{stroke:#e7c67e;stroke-width:1.7;stroke-dasharray:12 950;stroke-linecap:round;animation:circuit-flow 22s linear infinite;opacity:.65}.circuit-node{fill:#d7c28b;stroke:#e3d8a333;stroke-width:12}.lesson-heading{background:linear-gradient(90deg,#102b28ed, #102b28a0 55%,transparent);border-radius:0 0 22px 22px}.book-motion{display:block;margin:18px 0 0 auto;color:#d4dfce;background:#102c2880;border:1px solid #839b7860;border-radius:24px;padding:9px 14px;font-size:.72rem!important;cursor:pointer}.book-motion:disabled{opacity:.65;cursor:default}.solid-index a{backdrop-filter:blur(8px);background:#102b2866}.book-toolbar>span{padding:9px 12px;border-radius:20px;background:#0b2426cc}.book-tabs button{background:#16392f}.atmosphere-paused .circuit-signal{animation-play-state:paused}@keyframes circuit-flow{to{stroke-dashoffset:-1924}}@media(max-width:800px){.solid-atmosphere{opacity:.65}.book-motion{margin-top:14px}.lesson-heading{background:linear-gradient(90deg,#102b28ed,#102b28b0)}.circuit-signal{stroke-width:1.3}}@media(prefers-reduced-motion:reduce){.solid-atmosphere svg{transform:none!important}.circuit-signal{animation:none!important}}