:root{color-scheme:dark;--bg:#07121f;--bg2:#0a1726;--panel:#101f30;--panel2:#14263a;--line:#263a4d;--line2:#32495e;--text:#eff8ff;--muted:#a2b4c7;--muted2:#7890a6;--mint:#42d9ca;--mint-deep:#1e7776;--gold:#ffc36b;--blue:#7baaff;--purple:#b89dff;--chrome:#0b1928;--active:#17303a;--active-line:#2a5d62;--active-hover:#245652;--mint-hover:#81eee1;--on-mint:#06232a;--thumb:#d3fff7;--shadow:#02091480;font-family:'DM Sans',system-ui,-apple-system,'Segoe UI',sans-serif;font-synthesis:none}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--text);min-width:320px}button,input{font:inherit}button{cursor:pointer}button:focus-visible,input:focus-visible{outline:2px solid var(--mint);outline-offset:3px}button:disabled{cursor:not-allowed;opacity:.4}.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}
.site-shell{min-height:100vh}.topbar{height:76px;padding:0 35px;display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid var(--line);background:var(--chrome);position:relative;z-index:12}.brand,.topbar-right{display:flex;align-items:center}.brand{gap:12px}.brand-mark{position:relative;width:32px;height:32px;border:2px solid var(--mint);border-radius:50%;display:grid;place-items:center;transform:rotate(-30deg)}.brand-mark:before{content:'';position:absolute;width:37px;height:13px;border:2px solid var(--gold);border-radius:50%;transform:rotate(-25deg)}.brand-mark span{width:7px;height:7px;background:var(--text);border-radius:50%}.brand-word{font-family:'Space Grotesk',sans-serif;font-size:25px;font-weight:700;letter-spacing:-1.5px}.brand-dot{color:var(--mint)}.brand-divider{width:1px;height:20px;background:var(--line2);margin:0 2px}.brand-sub,.topbar-note{font-family:'Space Grotesk',sans-serif;color:var(--muted2);font-size:11px;font-weight:700;letter-spacing:2px}.topbar-note{letter-spacing:1.35px}.mobile-topics{display:none}
.layout{display:grid;grid-template-columns:292px minmax(0,1fr);min-height:calc(100vh - 76px)}.sidebar{background:var(--chrome);border-right:1px solid var(--line);display:flex;flex-direction:column;min-height:calc(100vh - 76px)}.sidebar-top{padding:29px 20px 12px}.sidebar-heading{display:flex;justify-content:space-between;align-items:center;font-family:'Space Grotesk',sans-serif;font-size:11px;color:var(--muted2);letter-spacing:1.25px;font-weight:700}.sidebar-heading span:last-child{font-size:10px;color:var(--mint);letter-spacing:.6px}.search-wrap{height:43px;border:1px solid var(--line2);background:var(--panel);display:flex;align-items:center;gap:8px;margin-top:22px;padding:0 11px;border-radius:8px;transition:border-color .2s}.search-wrap:focus-within{border-color:var(--mint)}.search-icon{font-size:22px;line-height:1;color:var(--muted2);transform:rotate(-25deg)}.search-wrap input{width:100%;min-width:0;background:none;border:0;outline:0;color:var(--text);font-size:14px}.search-wrap input::placeholder{color:var(--muted2)}.search-wrap kbd{font-size:12px;font-family:inherit;border:1px solid var(--line2);border-radius:4px;padding:1px 5px;color:var(--muted2)}.grade-tabs{display:flex;background:var(--bg2);padding:4px;border:1px solid var(--line);border-radius:9px;margin-top:20px;gap:3px}.grade-tab{border:0;border-radius:6px;background:transparent;color:var(--muted);font-size:14px;font-weight:700;flex:1;padding:9px 5px;transition:background .2s,color .2s}.grade-tab.active{background:var(--active);color:var(--mint);box-shadow:0 1px 4px var(--shadow)}.chapter-list{padding:7px 12px 26px;overflow:auto;max-height:calc(100vh - 291px);scrollbar-width:thin;scrollbar-color:var(--line2) transparent}.chapter-group{margin:13px 8px 9px;color:var(--muted2);font-size:10px;letter-spacing:1.55px;font-weight:700;font-family:'Space Grotesk',sans-serif}.chapter-link{width:100%;display:grid;grid-template-columns:24px 1fr 13px;align-items:center;gap:10px;border:1px solid transparent;border-radius:8px;background:none;color:var(--muted);padding:10px 10px;text-align:left;min-height:46px;font-size:14px;line-height:1.25;transition:background .2s,border .2s,color .2s}.chapter-link:hover{background:var(--panel2);color:var(--text)}.chapter-link.active{background:var(--active);border-color:var(--active-line);color:var(--mint)}.chapter-num{font-size:11px;font-family:'Space Grotesk',sans-serif;color:var(--muted2)}.chapter-link.active .chapter-num{color:var(--mint)}.chapter-arrow{opacity:0;color:var(--mint)}.chapter-link.active .chapter-arrow{opacity:1}.empty-search{font-size:14px;color:var(--muted);padding:20px 12px;line-height:1.5}.sidebar-bottom{margin-top:auto;padding:23px 25px;border-top:1px solid var(--line);color:var(--muted2);font-size:12px;display:flex;align-items:center;gap:10px}.tiny-orbit{font-size:23px;line-height:0;color:var(--mint)}
.main{width:100%;max-width:1560px;min-width:0;padding:34px clamp(24px,3.7vw,70px) 0;margin:0 auto}.workspace-header{display:flex;align-items:center;justify-content:space-between;gap:15px}.breadcrumbs{display:flex;align-items:center;gap:13px;min-width:0;font-size:11px;font-family:'Space Grotesk',sans-serif;letter-spacing:1.4px;font-weight:700;color:var(--muted2)}.breadcrumbs span:last-child{color:var(--mint);overflow:hidden;text-overflow:ellipsis;white-space:nowrap}.slash{color:var(--muted2)}.chapter-nav{display:flex;align-items:center;gap:11px;flex-shrink:0;font-family:'Space Grotesk',sans-serif;color:var(--muted2);font-size:11px;letter-spacing:1px}.chapter-nav button{height:31px;width:31px;border:1px solid var(--line2);border-radius:6px;background:var(--panel2);color:var(--text);font-size:16px}.chapter-nav button:hover{border-color:var(--mint);color:var(--mint)}.intro{display:flex;align-items:flex-end;justify-content:space-between;gap:26px;margin-top:37px;margin-bottom:28px}.intro-text{max-width:710px}.eyebrow{display:flex;gap:10px;align-items:center;font-size:10px;font-weight:700;color:var(--mint);font-family:'Space Grotesk',sans-serif;letter-spacing:1.9px}.eyebrow-line{height:1px;width:19px;background:var(--mint)}.eyebrow #sim-number{color:var(--muted2);margin-left:4px}.intro h1{margin:11px 0 8px;font-family:'Space Grotesk',sans-serif;font-size:clamp(31px,3.6vw,52px);line-height:1.07;letter-spacing:-2.5px;font-weight:700}.intro p{color:var(--muted);font-size:15px;line-height:1.65;margin:0}.formula-card{border:1px solid var(--line2);border-radius:10px;background:var(--panel);min-width:201px;padding:14px 19px;flex-shrink:0}.formula-card span{display:block;font-size:10px;letter-spacing:1.2px;font-weight:700;color:var(--muted2);font-family:'Space Grotesk',sans-serif}.formula-card strong{display:block;color:var(--gold);font-family:'Space Grotesk',sans-serif;font-size:17px;font-weight:500;margin-top:8px;white-space:nowrap}
.stage{background:var(--bg2);border:1px solid var(--line);border-radius:13px;overflow:hidden;box-shadow:0 12px 50px var(--shadow);position:relative}.stage-top,.stage-bottom{height:49px;display:flex;align-items:center;justify-content:space-between;padding:0 20px}.stage-top{border-bottom:1px solid var(--line)}.stage-bottom{border-top:1px solid var(--line);height:54px}.live-label,.stage-hint,.stage-brand{font-family:'Space Grotesk',sans-serif;font-size:10px;font-weight:700;letter-spacing:1.6px;color:var(--muted2)}.live-label{display:flex;align-items:center;gap:9px;color:var(--mint)}.live-dot{width:7px;height:7px;border-radius:50%;background:var(--mint);box-shadow:0 0 0 4px #42d9ca1b,0 0 12px #42d9ca88;animation:pulse 1.7s infinite}.stage.paused .live-dot{background:var(--muted2);box-shadow:none;animation:none}.stage.paused .live-label{color:var(--muted)}@keyframes pulse{50%{opacity:.4;box-shadow:0 0 0 7px #42d9ca09,0 0 22px #42d9ca88}}.stage-brand span{color:var(--mint);font-size:16px;vertical-align:middle}#simulation{display:block;width:100%;height:auto;aspect-ratio:960/505;background:var(--bg2);touch-action:none}.transport{display:flex;align-items:center;gap:10px}.transport button{display:inline-flex;align-items:center;justify-content:center;gap:7px;border-radius:6px;height:32px;font-size:12px;font-weight:700}.play-button{background:var(--mint);color:var(--on-mint);border:1px solid var(--mint);min-width:90px}.play-button:hover{background:var(--mint-hover)}.restart-button{color:var(--text);background:var(--panel2);border:1px solid var(--line2);padding:0 10px}.restart-button:hover{border-color:#668497}.restart-button span{font-size:19px;line-height:0}.transport-divider{height:22px;width:1px;background:var(--line2);margin:0 5px}.running-time{font-family:'Space Grotesk',sans-serif;color:var(--muted2);font-size:10px;letter-spacing:1.2px}.running-time strong{color:var(--text);font-size:12px;margin-left:5px;letter-spacing:.4px}
.below-stage{display:grid;grid-template-columns:minmax(0,1.5fr) minmax(285px,1fr);gap:17px;margin-top:18px}.controls-card,.observe-card{border:1px solid var(--line);border-radius:11px;background:var(--panel);padding:25px 25px 23px}.section-heading{display:flex;align-items:center;justify-content:space-between;gap:10px}.small-index{font-family:'Space Grotesk',sans-serif;font-size:10px;font-weight:700;letter-spacing:1.5px;color:var(--mint)}.section-heading h2{font-family:'Space Grotesk',sans-serif;font-size:19px;letter-spacing:-.5px;margin:5px 0 0}.section-heading button{border:0;background:none;color:var(--muted);font-size:12px;font-weight:700;white-space:nowrap;padding:8px 0}.section-heading button:hover{color:var(--mint)}.controls-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:27px 26px;margin-top:28px}.control-row{min-width:0}.control-label{display:flex;align-items:baseline;justify-content:space-between;gap:8px;margin-bottom:13px;font-size:13px;font-weight:700;color:var(--text)}.control-value{font-family:'Space Grotesk',sans-serif;color:var(--mint);font-size:14px;white-space:nowrap}.control-row input[type=range]{display:block;width:100%;height:7px;margin:0;appearance:none;border-radius:20px;background:linear-gradient(to right,var(--mint) 0 var(--fill),var(--line2) var(--fill) 100%);cursor:pointer}.control-row input[type=range]::-webkit-slider-thumb{appearance:none;width:18px;height:18px;border:3px solid var(--thumb);background:var(--mint);border-radius:50%;box-shadow:0 1px 6px #0008}.control-row input[type=range]::-moz-range-thumb{width:12px;height:12px;border:3px solid var(--thumb);background:var(--mint);border-radius:50%;box-shadow:0 1px 6px #0008}.control-extents{display:flex;justify-content:space-between;color:var(--muted2);font-size:11px;margin-top:10px}.control-row select{width:100%;height:39px;border:1px solid var(--line2);border-radius:6px;background:var(--panel2);color:var(--text);padding:0 10px;cursor:pointer}.observation{font-size:14px;color:var(--muted);line-height:1.65;min-height:46px;margin:17px 0 15px}.readouts{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:8px}.readout{border:1px solid var(--line2);background:var(--panel2);border-radius:7px;padding:11px 12px;min-width:0}.readout-label{display:block;color:var(--muted2);font-size:11px;line-height:1.3}.readout-value{display:block;font-family:'Space Grotesk',sans-serif;color:var(--text);font-size:17px;margin-top:4px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.try-box{display:flex;gap:11px;border-top:1px solid var(--line);padding-top:17px;margin-top:18px}.try-icon{color:var(--gold);font-size:18px}.try-box strong{font-family:'Space Grotesk',sans-serif;color:var(--gold);letter-spacing:1.3px;font-size:10px}.try-box p{color:var(--muted);font-size:12px;line-height:1.5;margin:5px 0 0}.footer{display:flex;justify-content:space-between;gap:20px;padding:27px 0 35px;color:var(--muted2);font-size:10px;letter-spacing:1.2px;font-family:'Space Grotesk',sans-serif;font-weight:700}
@media(max-width:1180px){.layout{grid-template-columns:260px minmax(0,1fr)}.main{padding-left:28px;padding-right:28px}.sidebar-top{padding-left:15px;padding-right:15px}.chapter-list{padding-left:8px;padding-right:8px}.formula-card{min-width:170px}.controls-grid{gap:25px 16px}}
@media(max-width:990px){.below-stage{grid-template-columns:1fr}.observation{min-height:0}.readouts{grid-template-columns:repeat(4,minmax(0,1fr))}.intro{align-items:flex-start}.formula-card{margin-top:19px}}
@media(max-width:760px){.topbar{height:64px;padding:0 17px}.brand-sub,.brand-divider,.topbar-note{display:none}.brand-word{font-size:23px}.mobile-topics{display:inline-flex;align-items:center;gap:9px;border:1px solid var(--line2);color:var(--text);background:var(--panel2);border-radius:7px;padding:9px 11px;font-size:12px;font-weight:700}.mobile-topics span{color:var(--mint)}.layout{display:block}.sidebar{display:none;position:absolute;z-index:11;top:64px;left:0;right:0;height:calc(100dvh - 64px);max-height:calc(100dvh - 64px);min-height:0;box-shadow:0 30px 40px #000b}.sidebar.open{display:flex}.chapter-list{max-height:none;flex:1}.main{padding:23px 17px 0}.intro{margin-top:30px;flex-direction:column;gap:15px;margin-bottom:20px}.intro h1{letter-spacing:-1.8px}.intro p{font-size:14px}.formula-card{margin-top:0;min-width:0;padding:11px 14px;align-self:flex-start}.formula-card strong{font-size:14px}.stage-top,.stage-bottom{padding:0 12px}.stage-hint,.stage-brand{display:none}.below-stage{gap:12px;margin-top:12px}.controls-card,.observe-card{padding:20px}.footer{flex-direction:column;gap:7px}.chapter-nav{gap:7px}}
@media(max-width:480px){.brand-mark{width:26px;height:26px}.brand-mark:before{width:31px;height:11px}.brand-word{font-size:21px}.workspace-header{gap:7px}.breadcrumbs{gap:7px;font-size:9px;letter-spacing:1px}.chapter-nav #position{display:none}.intro h1{font-size:32px}.controls-grid{grid-template-columns:1fr;gap:23px}.readouts{grid-template-columns:repeat(2,minmax(0,1fr))}.transport{gap:6px}.restart-button{font-size:0!important;min-width:35px;padding:0 8px!important}.restart-button span{font-size:20px}.running-time{font-size:9px}.running-time strong{display:block;font-size:11px;margin-left:0}.section-heading h2{font-size:18px}}

.simulation-tabs{display:flex;flex-wrap:wrap;gap:9px;margin:0 0 17px}.simulation-tabs button{border:1px solid var(--line2);background:var(--panel2);color:var(--muted);border-radius:8px;padding:12px 16px;min-height:44px;font-size:14px;text-align:left}.simulation-tabs button.selected{border-color:var(--mint);background:var(--active);color:var(--mint)}.simulation-tabs button:hover{border-color:#79acae}

.lesson-section{margin-top:18px;padding:25px;border:1px solid var(--line);border-radius:11px;background:var(--panel)}.lesson-section[hidden]{display:none}.lesson-top{display:flex;justify-content:space-between;align-items:center;gap:16px;flex-wrap:wrap}.lesson-top h2{font-size:19px;margin:0;letter-spacing:-.4px}.preset-buttons{display:flex;gap:9px;flex-wrap:wrap}.preset-buttons button{min-height:44px;padding:10px 15px;border:1px solid var(--active-line);border-radius:7px;background:var(--active);color:var(--mint);font-size:14px;font-weight:600}.preset-buttons button:hover{background:var(--active-hover)}.lesson-grid{display:grid;grid-template-columns:1.15fr 1fr;gap:24px;margin-top:22px;border-top:1px solid var(--line);padding-top:18px}.lesson-grid h3{font-size:12px;letter-spacing:1.4px;text-transform:uppercase;color:var(--muted2);margin:0 0 11px}.lesson-grid p{font-size:14px;line-height:1.65;margin:0;color:var(--muted)}.lesson-grid #worked-equation{color:var(--gold);font-size:16px;overflow-wrap:anywhere}.control-label{font-size:14px}.observation{font-size:15px}.readout-label{font-size:12px}.try-box p{font-size:14px}.formula-card{max-width:100%}.formula-card strong{white-space:normal}.intro-text{min-width:0}@media(max-width:760px){.lesson-section{padding:20px}.lesson-grid{grid-template-columns:1fr}.lesson-top{align-items:flex-start}.preset-buttons{width:100%}.preset-buttons button{flex:1}}

/* Theme palettes apply to navigation, lessons, controls, and the animation canvas. */
:root[data-theme="daylight"]{color-scheme:light;--bg:#f3f7fb;--bg2:#f7fbff;--chrome:#ffffff;--panel:#ffffff;--panel2:#eaf1f7;--line:#d0dee8;--line2:#b7cbda;--text:#16334a;--muted:#486276;--muted2:#587083;--mint:#007c73;--mint-deep:#005e57;--gold:#a85f00;--blue:#275fc5;--purple:#7543b8;--active:#dff3ed;--active-line:#63aea0;--active-hover:#c7e9de;--mint-hover:#00695f;--on-mint:#ffffff;--thumb:#ffffff;--shadow:#183d5714}
:root[data-theme="violet"]{color-scheme:dark;--bg:#120e22;--bg2:#1b132f;--chrome:#1c142e;--panel:#251b37;--panel2:#302440;--line:#453357;--line2:#5c4771;--text:#f3edff;--muted:#c2b4d3;--muted2:#a596bb;--mint:#c6a1ff;--mint-deep:#8055b6;--gold:#ffcd83;--blue:#8dbaff;--purple:#8fe3d8;--active:#392650;--active-line:#825da6;--active-hover:#4c3268;--mint-hover:#d9beff;--on-mint:#221332;--thumb:#f0e3ff;--shadow:#09051480}
:root[data-theme="chalkboard"]{color-scheme:dark;--bg:#0b1b17;--bg2:#10271f;--chrome:#10291f;--panel:#163127;--panel2:#203e31;--line:#315343;--line2:#466e57;--text:#eff6e8;--muted:#bdd0bb;--muted2:#9fb89f;--mint:#a9dfa0;--mint-deep:#5c9258;--gold:#f4d381;--blue:#96cbdc;--purple:#c9b8e4;--active:#284a32;--active-line:#6d9662;--active-hover:#365f3d;--mint-hover:#c4efba;--on-mint:#18321c;--thumb:#f1ffe9;--shadow:#020e0a80}
.topbar-right{gap:22px}.theme-picker{display:flex;align-items:center;gap:9px}.theme-picker>span{color:var(--muted2);font-size:10px;font-weight:700;letter-spacing:1.5px}.theme-picker select{font:inherit;font-size:13px;min-height:38px;width:120px;border:1px solid var(--line2);border-radius:7px;background:var(--panel2);color:var(--text);padding:0 9px;cursor:pointer}.theme-picker select:hover{border-color:var(--mint)}select:focus-visible{outline:2px solid var(--mint);outline-offset:3px}.live-dot{box-shadow:0 0 0 4px color-mix(in srgb,var(--mint) 12%,transparent)}@keyframes pulse{50%{opacity:.4;box-shadow:0 0 0 7px color-mix(in srgb,var(--mint) 7%,transparent)}}
@media(max-width:1100px){.topbar-note{display:none}}
@media(max-width:760px){.topbar-right{gap:10px}.theme-picker>span{display:none}.theme-picker select{width:116px}.mobile-topics{min-height:38px}.mobile-topics .browse-label{color:var(--text)}}
@media(max-width:480px){.topbar{padding:0 12px}.brand{gap:9px}.topbar-right{gap:7px}.mobile-topics{padding:8px 10px}.mobile-topics .browse-label{display:none}.theme-picker select{width:109px;font-size:12px}.topbar .brand-word{font-size:21px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}.live-dot{animation:none}*,*::before,*::after{transition:none!important}}

/* ---- Monochrome (black & white) themes ---- */
:root[data-theme="ink"]{color-scheme:dark;--bg:#0a0a0a;--bg2:#141414;--chrome:#111111;--panel:#181818;--panel2:#222;--line:#333;--line2:#454545;--text:#f6f6f6;--muted:#b4b4b4;--muted2:#8a8a8a;--mint:#ffffff;--mint-deep:#bdbdbd;--gold:#d8d8d8;--blue:#cfcfcf;--purple:#b6b6b6;--active:#242424;--active-line:#5a5a5a;--active-hover:#2e2e2e;--mint-hover:#ffffff;--on-mint:#0a0a0a;--thumb:#ffffff;--shadow:#00000080}
:root[data-theme="paper"]{color-scheme:light;--bg:#ffffff;--bg2:#fbfbfb;--chrome:#ffffff;--panel:#ffffff;--panel2:#f2f2f2;--line:#d8d8d8;--line2:#c4c4c4;--text:#101010;--muted:#515151;--muted2:#6e6e6e;--mint:#111111;--mint-deep:#000;--gold:#3a3a3a;--blue:#4a4a4a;--purple:#585858;--active:#ededed;--active-line:#9a9a9a;--active-hover:#e2e2e2;--mint-hover:#000;--on-mint:#ffffff;--thumb:#ffffff;--shadow:#0000001a}

/* ---- Top bar "Make your own" button ---- */
.build-btn{border:1px solid color-mix(in srgb,var(--gold) 55%,var(--line));background:linear-gradient(115deg,var(--panel),var(--active));color:var(--gold);border-radius:8px;min-height:40px;padding:0 16px;font-size:13px;font-weight:700;letter-spacing:.3px;transition:border-color .2s,transform .15s}
.build-btn:hover{border-color:var(--gold);transform:translateY(-1px)}

/* ---- Side control rail layout ---- */
.lab-layout{display:grid;grid-template-columns:minmax(0,1fr) 350px;gap:18px;align-items:start;margin-top:2px}
.lab-main{min-width:0}
.lab-main .physics-panel{margin-top:18px}
.side-rail{position:sticky;top:16px;min-width:0}
.side-rail .controls-card{padding:22px 22px 24px;max-height:calc(100vh - 40px);overflow:auto;scrollbar-width:thin;scrollbar-color:var(--line2) transparent}
.side-rail .controls-grid{grid-template-columns:1fr;gap:24px;margin-top:22px}
.rail-buttons{display:flex;align-items:center;gap:8px}
.rail-buttons #defaults{border:0;background:none;color:var(--muted);font-size:12px;font-weight:700;padding:6px 0;white-space:nowrap}
.rail-buttons #defaults:hover{color:var(--mint)}
.rail-toggle{width:34px;height:34px;border:1px solid var(--line2);border-radius:7px;background:var(--panel2);color:var(--text);font-size:15px;line-height:1}
.rail-toggle:hover{border-color:var(--mint);color:var(--mint)}
.lab-layout.rail-collapsed{grid-template-columns:minmax(0,1fr) 54px}
.lab-layout.rail-collapsed .controls-grid,.lab-layout.rail-collapsed .section-heading>div:first-child,.lab-layout.rail-collapsed #defaults{display:none}
.lab-layout.rail-collapsed .side-rail .controls-card{padding:10px 8px;overflow:visible}
.lab-layout.rail-collapsed .rail-buttons{justify-content:center}
.below-stage{grid-template-columns:1fr}
@media(max-width:1180px){.lab-layout{grid-template-columns:minmax(0,1fr) 300px}}
@media(max-width:990px){.lab-layout{grid-template-columns:1fr}.side-rail{position:static;max-height:none}.side-rail .controls-card{max-height:none}.side-rail .controls-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.lab-layout.rail-collapsed{grid-template-columns:1fr}.lab-layout.rail-collapsed .controls-grid,.lab-layout.rail-collapsed .section-heading>div:first-child,.lab-layout.rail-collapsed #defaults{display:revert}}
@media(max-width:560px){.side-rail .controls-grid{grid-template-columns:1fr}.build-btn{padding:0 11px;font-size:12px}}


/* Teaching tools extend the existing theme instead of creating a separate skin. */
.lab-tools{display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:12px;margin:0 0 16px}.lab-tool-buttons{display:flex;align-items:center;flex-wrap:wrap;gap:8px}.lab-tools button,.wonder-card button{min-height:44px;border:1px solid var(--line2);background:var(--panel);color:var(--text);border-radius:8px;padding:10px 16px;font-size:14px;font-weight:650}.lab-tools button:hover,.wonder-card button:hover{border-color:var(--mint)}.lab-tools button[aria-pressed=true]{background:var(--active);border-color:var(--active-line);color:var(--mint)}.lab-tools .surprise-button{color:var(--gold);border-color:color-mix(in srgb,var(--gold) 45%,var(--line));background:linear-gradient(115deg,var(--panel),var(--active));display:flex;align-items:center;gap:11px}.surprise-button span{font-size:19px}.volume-control{display:flex;align-items:center;gap:8px;color:var(--muted);font-size:13px}.volume-control input{width:78px;accent-color:var(--mint)}.volume-control[hidden],.sound-caption[hidden],.wonder-card[hidden],.wonder-answer[hidden],.physics-panel[hidden]{display:none}.sound-caption{width:100%;font-size:13px;color:var(--muted2)}
.wonder-card{position:relative;margin:0 0 18px;border:1px solid var(--active-line);border-radius:12px;background:linear-gradient(115deg,var(--panel),var(--active));padding:25px 58px 25px 25px;box-shadow:inset 4px 0 var(--gold)}.wonder-copy h2{font-size:22px;letter-spacing:-.4px;margin:9px 0}.wonder-copy p{font-size:16px;line-height:1.65;color:var(--muted);max-width:850px;margin:10px 0 17px}.wonder-copy .wonder-answer{color:var(--text);border-top:1px solid var(--active-line);padding-top:17px;margin-bottom:0}.wonder-copy button{color:var(--mint);background:var(--bg2)}.wonder-card .wonder-close{position:absolute;top:12px;right:12px;min-height:36px;width:36px;padding:0;font-size:24px;background:none;border-color:transparent;color:var(--muted)}
.physics-panel{margin-top:18px;border:1px solid var(--active-line);border-radius:12px;background:var(--panel);overflow:hidden}.physics-heading{padding:22px 25px 19px;border-bottom:1px solid var(--line)}.physics-heading h2{font-size:21px;line-height:1.3;margin:7px 0 0;letter-spacing:-.4px}.physics-grid{display:grid;grid-template-columns:minmax(0,1.25fr) minmax(260px,1fr)}.physics-visual{min-width:0;background:var(--bg2);border-right:1px solid var(--line)}#physics-canvas{display:block;width:100%;height:auto;aspect-ratio:640/330}.physics-scale{font-size:13px;color:var(--muted2);line-height:1.5;margin:0;padding:14px 20px 20px}.physics-explanation{padding:20px 23px}.physics-explanation>p{font-size:16px;line-height:1.65;color:var(--text);margin:0 0 18px}.physics-values{display:grid;gap:9px}.lens-value{display:flex;justify-content:space-between;align-items:baseline;gap:14px;border-bottom:1px solid var(--line);padding:8px 0}.lens-value:last-child{border-bottom:0}.lens-value span{font-size:13px;line-height:1.4;color:var(--muted)}.lens-value strong{font-size:16px;font-weight:650;color:var(--mint);text-align:right}.model-reference{display:inline-block;margin-top:15px;color:var(--mint);font-size:14px;line-height:1.5;text-underline-offset:4px}
@media(max-width:990px){.physics-grid{grid-template-columns:1fr}.physics-visual{border-right:0;border-bottom:1px solid var(--line)}.physics-values{grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}.lens-value{display:block;border:0}.lens-value span,.lens-value strong{display:block;text-align:left}.lens-value strong{margin-top:5px}}
@media(max-width:600px){.lab-tools{gap:8px}.lab-tools button{padding:10px 12px}.lab-tool-buttons{gap:7px}.wonder-card{padding:20px 45px 20px 20px}.wonder-copy h2{font-size:20px}.physics-heading{padding:20px}.physics-heading h2{font-size:19px}.physics-explanation{padding:18px 20px}.physics-values{grid-template-columns:1fr}.lens-value{display:flex}.lens-value strong{text-align:right;margin:0}}
@media(max-width:390px){.lab-tools{align-items:stretch}.lab-tools .surprise-button{justify-content:center}.lab-tool-buttons{flex:1}.lab-tools button{font-size:13px;padding:10px}.lab-tools .surprise-button span{display:none}}

/* Personal library and precision controls keep the original Physica palette. */
.favourites{margin:4px 20px 14px;padding:15px 0;border-bottom:1px solid var(--line)}#favourites-list{max-height:210px;overflow:auto;margin-top:10px;scrollbar-width:thin}.favourites-empty{font-size:12px;color:var(--muted2);line-height:1.6;margin:0}.favourite-row{display:flex;gap:5px;margin:4px 0}.favourite-row button{background:transparent;border:0;color:var(--muted);text-align:left;min-height:40px;border-radius:6px;font-size:13px;padding:8px;transition:background-color .2s,color .2s}.favourite-row button:first-child{flex:1;min-width:0}.favourite-row button:hover,.favourite-row button.active{background:var(--active);color:var(--mint)}.favourite-row .favourite-remove{color:var(--gold);flex-shrink:0;width:34px;font-size:19px}#favourites-status:empty{display:none}#favourites-status{font-size:12px;color:var(--gold)}
.exact-value{width:100%;border:1px solid var(--line2);background:var(--panel2);color:var(--text);border-radius:6px;padding:8px 10px;margin-top:9px;min-height:38px}.simulation-playback{margin-top:22px;border-top:1px solid var(--line);padding-top:18px;display:grid;gap:10px;font-size:13px}.simulation-playback select,.simulation-playback button{font:inherit;min-height:38px;background:var(--panel2);color:var(--text);border:1px solid var(--line2);border-radius:6px;padding:8px}.simulation-playback p{color:var(--muted2);line-height:1.5;margin:0}.rail-collapsed .simulation-playback{display:none}.chapter-list{max-height:none}.sidebar{max-height:calc(100vh - 76px);position:sticky;top:0}.sidebar-top,.favourites,.sidebar-bottom{flex-shrink:0}.chapter-list{flex:1;min-height:120px}
@media(max-width:760px){.topbar{height:auto;min-height:76px;flex-wrap:wrap;padding-top:12px;padding-bottom:12px;gap:12px}.topbar-right{flex-wrap:wrap}.sidebar{position:absolute;top:100%;max-height:calc(100dvh - 110px);height:calc(100dvh - 110px)}.layout{position:relative}.layout .sidebar{top:0}.favourites{margin:0 20px 8px}.sidebar-bottom{display:none}.favourites #favourites-list{max-height:140px}.sidebar-top{padding-top:18px}.search-wrap{margin-top:12px}}