:root{--ink:#142d42;--soft:#3f5867;--muted:#647982;--paper:#faf9f5;--white:#fff;--line:#d5ddd9;--gold:#ac813d;--gold-soft:#f0e4cc;--teal:#287784;--pale:#dcebef;--red:#9a4435;--serif:Georgia,'Times New Roman',serif;--sans:system-ui,-apple-system,'Segoe UI',sans-serif}
*{box-sizing:border-box}body{margin:0;color:var(--ink);background:var(--paper);font:16px/1.55 var(--sans);-webkit-font-smoothing:antialiased}h1,h2,h3,p,figure{margin:0}a{color:var(--soft);text-underline-offset:4px}button,input,select{font:inherit;color:inherit}button,a,input,select,summary{-webkit-tap-highlight-color:transparent}button,summary{cursor:pointer}button,select{min-height:40px}button{border:1px solid var(--line);border-radius:3px;background:transparent;padding:8px 12px;transition:background .16s,border-color .16s}button:hover{background:#edf0eb;border-color:#8da2a8}button[aria-pressed=true],button[aria-selected=true],button.primary{background:var(--ink);color:white;border-color:var(--ink)}button:disabled{opacity:.5;cursor:default}button:focus-visible,a:focus-visible,summary:focus-visible,canvas:focus-visible{outline:2px solid var(--gold);outline-offset:3px}input,select{background:white;border:1px solid #b8c7cc;border-radius:3px;padding:9px 10px;min-width:0;width:100%}input:focus-visible,select:focus-visible{outline:2px solid var(--gold);outline-offset:1px}input[type=range]{accent-color:var(--teal);padding:0;border:0;min-height:30px;background:transparent}input[type=checkbox]{width:auto;accent-color:var(--teal)}button small{font-size:11px}label{display:block;font-size:13px;color:var(--soft);margin-bottom:6px}strong{font-weight:600}.loading{padding:40px}.app-header{height:77px;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;gap:18px;padding:12px 32px}.brand{display:flex;gap:14px;align-items:center}.brand-mark{font:italic 33px var(--serif);width:43px;height:43px;display:grid;place-items:center;background:var(--ink);color:#e4c887;border-radius:4px}.brand h1{font:28px/1 var(--serif);letter-spacing:-.025em}.brand p{font-size:11px;letter-spacing:.1em;margin-top:5px;text-transform:uppercase;color:var(--muted)}.header-actions{display:flex;align-items:center;gap:14px}.header-actions a{font-size:13px;text-decoration:none}.lang{display:flex;gap:3px}.lang button{padding:5px 9px;font-size:12px;min-height:34px}.module-nav{display:flex;gap:5px;border-bottom:1px solid var(--line);padding:10px 32px;background:#f3f4ef}.module-nav button{border-color:transparent;font-size:14px;display:flex;align-items:center;gap:10px}.module-nav button span{font:11px var(--serif);color:var(--gold)}.module-nav button[aria-selected=true]{background:#fff;color:var(--ink);border-color:var(--line)}.app-main{max-width:1700px;margin:auto;padding:25px 32px 30px}.page-intro{display:flex;align-items:start;justify-content:space-between;gap:25px;margin-bottom:20px}.page-intro h2{font:clamp(25px,2.7vw,37px)/1.18 var(--serif);letter-spacing:-.025em}.page-intro p{font-size:14px;color:var(--muted);margin-top:7px;max-width:810px}.layer{display:inline-flex;align-items:center;gap:8px;font-size:10px;letter-spacing:.085em;text-transform:uppercase;border:1px solid var(--line);border-radius:3px;padding:7px 10px;white-space:nowrap;align-self:start}.layer:before{content:'';width:6px;height:6px;border-radius:50%;background:var(--teal)}.layer.numerical:before{background:var(--gold)}.layer.finite:before{background:#857197}.workspace{display:grid;grid-template-columns:minmax(0,1fr) 305px;gap:24px;align-items:start}.visual-column{min-width:0}.stage-card{border:1px solid var(--line);border-radius:4px;background:#fff;overflow:hidden;position:relative}.stage-toolbar{display:flex;align-items:center;justify-content:space-between;gap:10px;padding:12px 15px;border-bottom:1px solid var(--line);min-height:63px}.view-tabs{display:flex;flex-wrap:wrap;gap:4px}.view-tabs button{font-size:12px;padding:7px 10px;min-height:34px}.scene-actions{display:flex;gap:4px}.scene-actions button{width:33px;min-height:34px;padding:0;font-size:18px}.scene{height:clamp(380px,52vh,620px);position:relative;overflow:hidden;background:#f7f9f6;isolation:isolate}.scene canvas{position:absolute;inset:0;width:100%;height:100%}.scene canvas#plot{z-index:2;touch-action:none;cursor:grab}.scene canvas#cloud{z-index:3;pointer-events:none}.scene:active canvas#plot{cursor:grabbing}.scene-note{position:absolute;bottom:10px;left:16px;right:12px;font-size:11px;color:var(--muted);z-index:5;pointer-events:none;display:flex;justify-content:space-between;gap:10px}.scene-label{position:absolute;top:13px;left:16px;z-index:5;pointer-events:none;font:italic 20px var(--serif);color:var(--soft);background:#f7f9f6e8;padding:0 4px}.busy{position:absolute;right:14px;top:14px;font-size:12px;background:var(--paper);padding:5px 9px;border:1px solid var(--line);z-index:5}.busy[hidden]{display:none}.legend{display:flex;flex-wrap:wrap;gap:8px 20px;padding:11px 16px;border-top:1px solid var(--line);font-size:11px;color:var(--soft);min-height:41px}.legend span{display:inline-flex;gap:7px;align-items:center}.legend i{display:inline-block;width:10px;height:10px;border-radius:1px}.metrics{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));border:1px solid var(--line);border-radius:4px;margin-top:15px;background:white}.metric{min-width:0;padding:13px 18px;border-right:1px solid var(--line)}.metric:last-child{border:0}.metric .label{font-size:12px;color:var(--muted)}.metric .number{font:29px/1.3 var(--serif);margin:3px 0;color:var(--ink)}.metric:last-child .number{color:var(--gold)}.metric small{font-size:11px;color:var(--muted);display:block}.reading{margin-top:17px;padding:18px 20px;border-left:2px solid var(--gold);background:#f2eee4;font-size:14px;line-height:1.7}.reading p+p{margin-top:10px}.reading .math-line{margin:8px 0}.reading strong{color:var(--ink)}.sidebar{min-width:0;border-top:2px solid var(--ink);padding-top:16px}.control-group{padding:0 0 17px;margin-bottom:17px;border-bottom:1px solid var(--line)}.control-group:last-child{border-bottom:0}.control-group h3{font:20px var(--serif);margin-bottom:13px}.control-group .eyebrow{font-size:10px;letter-spacing:.15em;text-transform:uppercase;color:var(--gold);margin-bottom:5px}.control-group p,.help{font-size:12px;line-height:1.65;color:var(--muted);margin-top:9px}.control-row{display:flex;align-items:center;gap:7px;margin-top:8px}.control-row>*{min-width:0;flex:1}.control-row button{font-size:12px;padding:7px 10px}.range-title{display:flex;justify-content:space-between;align-items:baseline;gap:10px}.range-title output{font:23px var(--serif)}.field{margin-top:12px}.field input{font-size:14px}.field-grid{display:grid;grid-template-columns:1fr 1fr;gap:10px}.region-list{display:flex;gap:4px;flex-wrap:wrap;margin:10px 0}.region-list button{font-size:11px;min-height:31px;padding:5px 8px}.tiny{font-size:11px!important}.error{border-left:3px solid var(--red);background:#faeee7;color:#823a2d;font-size:13px;padding:12px;margin-top:10px}.error:empty{display:none}.math-line{max-width:100%;overflow-x:auto;overflow-y:hidden;font-size:14px}.math-line mjx-container[display=true]{margin:.5em 0!important}mjx-container{max-width:100%}details{font-size:13px;color:var(--soft)}summary{padding:8px 0;font-weight:500}details p{margin:9px 0}details .math-line{font-size:13px}.proof-steps{display:flex;gap:4px;flex-wrap:wrap;margin:10px 0}.proof-steps button{font-size:11px;min-height:32px;padding:5px 8px}.proof-bar{height:10px;display:flex;background:#e3eae9;border-radius:1px;overflow:hidden;margin-top:10px}.proof-bar span{background:var(--gold);min-width:1px}.proof-bar span+span{background:var(--teal)}.footline{display:flex;justify-content:space-between;flex-wrap:wrap;gap:12px;font-size:11px;color:var(--muted);border-top:1px solid var(--line);margin-top:24px;padding-top:15px}.footline a{color:var(--muted)}.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}.state-info{font-size:12px;line-height:1.6;margin-top:8px}.success{color:#236476}.formula-card{padding:12px 13px;border:1px solid var(--line);background:white;border-radius:3px;margin:10px 0}.formula-card p{font-size:12px}.proof-table{width:100%;border-collapse:collapse;margin-top:10px;font-size:12px}.proof-table td,.proof-table th{text-align:left;padding:5px;border-bottom:1px solid var(--line)}.proof-table th{font-weight:500}.on-mobile{display:none}[hidden]{display:none!important}
@media(min-width:1500px){.workspace{grid-template-columns:minmax(0,1fr) 330px}.scene{height:610px}}
@media(max-width:1000px){.app-header{padding-inline:20px}.module-nav{padding-inline:20px}.app-main{padding:22px 20px}.workspace{gap:18px;grid-template-columns:minmax(0,1fr) 270px}.page-intro{flex-direction:column;gap:9px}.scene{height:450px}.stage-toolbar{align-items:start;flex-direction:column}.scene-actions{position:absolute;top:14px;right:10px}.view-tabs{padding-right:75px}.metric{padding:12px}.metric .number{font-size:26px}}
@media(max-width:760px){.app-header{height:72px;padding:10px 16px}.brand{gap:9px}.brand h1{font-size:25px}.brand-mark{width:35px;height:35px;font-size:28px}.brand p{font-size:9px;max-width:180px}.header-actions{gap:8px}.header-actions a{font-size:11px}.module-nav{display:grid;grid-template-columns:1fr 1fr;padding:8px 12px;gap:4px}.module-nav button{font-size:12px;min-height:37px;gap:8px;padding:7px 9px}.app-main{padding:19px 14px}.page-intro h2{font-size:27px}.page-intro p{font-size:13px}.layer{font-size:9px;white-space:normal}.workspace{display:flex;flex-direction:column;gap:22px}.visual-column,.sidebar{width:100%}.visual-column{order:0}.sidebar{order:1}.scene{height:350px}.stage-toolbar{padding:10px 11px;min-height:58px}.view-tabs{padding-right:66px;gap:4px}.view-tabs button{font-size:11px;padding:6px 8px;min-height:32px}.scene-actions{top:11px;right:8px;gap:2px}.scene-actions button{width:28px;min-height:32px}.scene-note{font-size:9px;left:12px;bottom:8px}.scene-label{font-size:16px;top:10px;left:12px}.legend{font-size:10px;gap:6px 13px;padding:10px 11px}.metric{padding:10px 11px}.metric .label{font-size:10px}.metric .number{font-size:24px}.metric small{font-size:10px}.reading{padding:14px;font-size:13px}.math-line{font-size:12px}.on-mobile{display:inline}.control-group{margin-bottom:16px}.control-group h3{font-size:23px}.control-group p,.help{font-size:13px}.control-group label{font-size:14px}.control-row button{font-size:13px;min-height:41px}.lang button{font-size:11px;padding:4px 6px;min-height:31px}.header-actions .home-label{display:none}.footline{font-size:10px}.proof-steps button{min-height:38px;font-size:12px}}
@media(prefers-reduced-motion:reduce){*,*:before,*:after{transition:none!important;scroll-behavior:auto!important}}

/* Shared laboratory button language, with explicit return navigation. */
button,.app-button{border-radius:6px;background:#fff;border:1px solid #bdc8ce;font-weight:600;transition:transform .12s ease,box-shadow .12s ease,border-color .12s ease,background .12s ease}
button:hover,.app-button:hover{transform:translateY(-1px);box-shadow:0 6px 15px rgba(23,32,51,.085);border-color:#8da2a8}
button[aria-pressed=true],button.primary{background:var(--ink);color:white;border-color:var(--ink)}
.app-button{display:inline-flex;align-items:center;justify-content:center;gap:7px;min-height:40px;padding:.5rem .72rem;text-decoration:none;color:var(--ink)}
.header-actions .back-button{font-size:14px;white-space:nowrap}
.module-nav button{font-weight:500}.lang{padding:3px;border:1px solid var(--line);border-radius:7px;background:#eef1f0}.lang button{min-height:32px}
.learn-bar{display:flex;justify-content:flex-end;margin:-7px 0 18px}.learn-bar button{font-size:12px;min-height:34px;color:var(--soft)}
.sum-switch{display:flex;gap:4px;flex-wrap:wrap;padding:8px 14px;background:#f0f3f0;border-bottom:1px solid var(--line)}
.sum-switch button{font-size:12px;min-height:34px;padding:6px 11px}.sum-comparison{height:490px}
.sum-switch .quick-refine{margin-left:auto;background:#e8efed;color:var(--teal);border-color:#adbfbd}
.sum-history{background:white;border:1px solid var(--line);border-radius:6px;padding:16px 18px;margin-top:16px;min-width:0}
.history-heading{display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:10px}.history-heading h3{font:21px var(--serif)}
.history-heading span{font-size:12px;color:var(--muted)}.lower-dot,.upper-dot{display:inline-block;width:9px;height:9px;border-radius:50%;background:var(--teal);margin:0 5px 0 9px}.upper-dot{background:var(--gold)}
.sum-chart{width:100%;height:auto;display:block;min-height:150px;margin:8px 0}.sum-chart text{fill:var(--muted);font:12px var(--sans)}
.history-table{width:100%;font-size:13px;border-collapse:collapse}.history-table td,.history-table th{padding:7px 5px;border-bottom:1px solid var(--line);text-align:right}.history-table td:first-child,.history-table th:first-child{text-align:left}
.reference-note{padding:12px 14px;border:1px solid #d7c7a7;border-radius:5px;background:#fffaf0;margin:12px 0;font-size:14px}
.foundations{margin-top:25px;scroll-margin-top:18px}.definition-card{background:#fff;border:1px solid var(--line);border-radius:6px;padding:14px 20px;font-size:15px;line-height:1.75;scroll-margin-top:20px}
.definition-card>summary{font:23px var(--serif);color:var(--ink);padding:5px 0}.definition-card h3,.complete-proof h3{font:22px var(--serif);color:var(--ink);margin:20px 0 8px}
.definition-card .math-line{font-size:17px}.complete-proof .math-line{font-size:16px}
.definition-grid{display:grid;grid-template-columns:1fr 1fr;gap:24px;margin:12px 0}.definition-grid>div{padding:0 18px 16px;background:#f4f6f2;border-left:3px solid var(--teal)}.definition-grid>div+div{border-color:var(--gold)}
.complete-proof{margin-top:18px;padding-top:12px;border-top:1px solid #d8cbaa;font-size:15px;line-height:1.8}.complete-proof>summary{font-size:16px;color:var(--ink)}
.reading p,.complete-proof p{overflow-wrap:break-word}.metric .label .math{font-size:13px}.metric .number{font-variant-numeric:tabular-nums}.control-group label{font-size:14px}.control-group p,.help{font-size:13px}
.control-row #previous-step{flex:0 0 38px}.field:disabled,input:disabled{opacity:.5;cursor:not-allowed}
.range-title output{white-space:nowrap;flex-shrink:0}
@media(max-width:1200px) and (min-width:761px){.sum-comparison{height:690px}}
@media(max-width:760px){
 .app-header{height:auto;min-height:64px;flex-wrap:wrap;gap:8px;padding:10px 12px}.header-actions{margin-left:auto;gap:6px}.header-actions .home-label{display:inline}.header-actions .back-button{font-size:12px;min-height:40px;padding:7px 8px}
 .brand p{display:none}.brand h1{font-size:25px}.brand-mark{width:33px;height:33px}.brand{gap:7px}.lang button{padding:5px 6px}
 .page-intro p{display:none}.page-intro h2{font-size:25px}.module-nav{padding-block:6px}.learn-bar{margin-bottom:10px}
 .learn-bar{margin:0 0 13px;justify-content:flex-start}.learn-bar button{font-size:12px;text-align:left}
 .sum-switch{padding:8px;gap:4px}.sum-switch button{font-size:11px;padding:7px;min-height:36px}.sum-comparison{height:655px}
 .history-heading h3{font-size:21px}.sum-history{padding:14px 10px}.sum-chart{min-height:135px}.definition-card{padding:14px;font-size:14px}.definition-card>summary{font-size:22px}.definition-grid{grid-template-columns:1fr;gap:12px}.definition-grid>div{padding:0 12px 12px}
 .complete-proof{font-size:14px}.complete-proof h3{font-size:21px}.metric .label .math{font-size:11px}.metric .number{font-size:22px}.reference-note{font-size:13px}.control-group p{font-size:13px}
 .definition-card .math-line,.complete-proof .math-line{font-size:14px}
}