:root {
  font-family: Inter, 'Segoe UI', system-ui, sans-serif;
  color: #dbe7f0;
  background: #101822;
  font-synthesis: none;
  color-scheme: dark;
  --mint: #91e2cb;
  --muted: #98adbf;
  --border: #2a394a;
}
* { box-sizing: border-box; }
[hidden] { display: none !important; }
body { margin: 0; }
button, select, input { font: inherit; }
button, select { color: inherit; }
button, a, select, input { -webkit-tap-highlight-color: transparent; }
button { cursor: pointer; }
a { color: var(--mint); text-underline-offset: 4px; }
button:focus-visible, a:focus-visible, select:focus-visible, input:focus-visible, canvas:focus-visible, summary:focus-visible { outline: 2px solid var(--mint); outline-offset: 4px; }
.app-header { min-height: 96px; display: flex; align-items: center; gap: 22px; padding: 20px 32px; border-bottom: 1px solid var(--border); background: #121d29; }
.brand { flex-shrink: 0; font: 700 19px monospace; text-decoration: none; color: var(--mint); border: 1px solid #3c7069; border-radius: 9px; padding: 15px 12px; }
.brand span { color: #516a79; padding: 0 3px; }
h1 { font-size: 19px; font-weight: 600; margin: 0; }
.header-title p { margin: 6px 0 0; color: var(--muted); font-size: 13px; }
.status { margin-left: auto; color: var(--mint); font: 10px monospace; letter-spacing: 1px; white-space: nowrap; display: flex; align-items: center; gap: 8px; }
.status i { background: var(--mint); width: 6px; height: 6px; border-radius: 50%; }
.subjects { background: #121d29; border-bottom: 1px solid var(--border); overflow-x: auto; padding: 0 24px; }
[role='tablist'] { display: flex; min-width: max-content; }
[role='tab'] { display: flex; align-items: center; gap: 9px; background: transparent; border: 0; border-bottom: 2px solid transparent; padding: 20px 13px; font-size: 12px; color: var(--muted); white-space: nowrap; }
[role='tab'] span { color: #71899d; font: 10px monospace; }
[role='tab']:hover { background: #1b2b3a; color: #dbe7f0; }
[role='tab'][aria-selected='true'] { color: var(--mint); border-bottom-color: var(--mint); background: #192b32; }
[role='tab'][aria-selected='true'] span { color: var(--mint); }
main { display: grid; grid-template-columns: 310px minmax(0, 1fr); min-height: calc(100dvh - 153px); }
.controls-panel { padding: 28px 25px; border-right: 1px solid var(--border); background: #15212e; }
.eyebrow { font: 10px monospace; color: var(--mint); letter-spacing: 2px; margin: 0 0 14px; }
h2 { font-size: 26px; font-weight: 550; letter-spacing: -0.5px; line-height: 1.25; margin: 0 0 15px; }
p { line-height: 1.7; }
.description { color: var(--muted); font-size: 13px; margin: 0 0 30px; }
.parameter { margin: 24px 0; }
.parameter-label { display: flex; align-items: baseline; justify-content: space-between; gap: 8px; }
label { font-size: 12px; color: #c2d0dd; }
output { flex-shrink: 0; color: var(--mint); font: 12px monospace; }
input[type='range'] { display: block; width: 100%; accent-color: var(--mint); margin: 14px 0 0; cursor: pointer; }
input:disabled { opacity: 0.35; cursor: default; }
select { display: block; width: 100%; padding: 10px 8px; border: 1px solid #3b4d60; border-radius: 6px; background: #1c2c3d; margin-top: 10px; font-size: 12px; }
.panel-actions button { width: 100%; border: 1px solid #3b4d60; border-radius: 6px; background: #1c2c3d; padding: 11px; font-size: 12px; }
button:hover { border-color: var(--mint); }
.measurements { margin-top: 25px; border: 1px solid #2a4252; border-radius: 8px; padding: 4px 16px; background: #101c27; }
.measurement { padding: 14px 0; }
.measurement + .measurement { border-top: 1px solid #243342; }
.measurement > span { display: block; font-size: 11px; color: var(--muted); }
.measurement > div { display: flex; align-items: baseline; gap: 8px; margin-top: 6px; }
.measurement strong { font: 23px monospace; color: var(--mint); }
.measurement small { font-size: 11px; color: var(--muted); }
.workbench { min-width: 0; }
#viewport { position: relative; height: clamp(480px, 64dvh, 800px); min-width: 0; overflow: hidden; }
#viewport > canvas { display: block; position: absolute; inset: 0; width: 100%; height: 100%; touch-action: none; }
.scene-labels { position: absolute; inset: 0; pointer-events: none; z-index: 0; overflow: hidden; container-type: inline-size; }
.scene-math-label { pointer-events: none; white-space: nowrap; padding: 2px 5px; border-radius: 3px; background: #101822d9; font-size: 13px; line-height: 1.5; }
@container (max-width: 599px) { .scene-math-label { font-size: 11px; } }
.scene-toolbar { position: absolute; z-index: 1; top: 20px; left: 24px; right: 24px; display: flex; justify-content: space-between; align-items: center; gap: 10px; pointer-events: none; }
.view-tag { font: 10px monospace; color: #71899d; letter-spacing: 2px; }
.scene-toolbar > div { display: flex; gap: 8px; }
.scene-toolbar button { pointer-events: auto; background: #15212ee8; border: 1px solid #34495c; border-radius: 5px; padding: 7px 10px; font-size: 11px; }
.legend { position: absolute; z-index: 1; pointer-events: none; left: 24px; top: 64px; display: flex; flex-wrap: wrap; gap: 8px 18px; right: 24px; }
.legend span { display: flex; align-items: center; gap: 6px; color: var(--muted); font-size: 10px; }
.legend i { display: inline-block; width: 5px; height: 5px; border-radius: 50%; }
.scene-footer { position: absolute; z-index: 1; pointer-events: none; bottom: 0; padding: 24px 24px 12px; width: 100%; background: linear-gradient(transparent, #101822ed); }
.scene-footer p { margin: 3px 0; color: #b3c8d7; font-size: 11px; line-height: 1.6; }
.scene-footer .hint { color: #7890a4; font-size: 10px; }
.learning-panel { display: grid; grid-template-columns: 1.3fr 1fr; gap: 36px; padding: 28px 32px; border-top: 1px solid var(--border); background: #121d29; }
.learning-panel p { font-size: 13px; color: var(--muted); margin: 12px 0; }
.learning-panel .eyebrow { color: var(--mint); font-size: 10px; margin: 0 0 14px; }
.learning-panel > div { min-width: 0; }
.equations p { color: #e3ecf3; font-size: 16px; margin: 8px 0; }
.learning-panel a { font-size: 11px; }
.challenge { border-left: 1px solid var(--border); padding-left: 30px; }
.challenge > p:not(.eyebrow) { color: #cad8e4; }
details { margin-top: 20px; }
summary { color: var(--muted); font-size: 11px; cursor: pointer; }
.collections { display: flex; align-items: center; gap: 5px; margin-left: auto; padding: 4px; background: #0c151f; border: 1px solid var(--border); border-radius: 8px; flex-shrink: 0; }
.collections a { color: var(--muted); text-decoration: none; font-size: 12px; padding: 10px 13px; border-radius: 5px; }
.language-picker { display: flex; align-items: center; gap: 8px; margin-left: 6px; padding: 0 8px 0 10px; border-left: 1px solid var(--border); color: var(--muted); font-size: 12px; }
.language-picker select { width: auto; margin: 0; padding: 8px 8px; }
.collections a[aria-current] { background: #234139; color: #b0f3dc; }
.test-overview { display: flex; justify-content: space-between; align-items: center; gap: 32px; padding: 30px 34px; background: radial-gradient(ellipse at 80% 0%, #20413988, transparent 65%), #121d29; border-bottom: 1px solid var(--border); }
.test-overview .eyebrow { font-size: 9px; margin-bottom: 10px; }
.test-overview h2 { font-size: clamp(22px, 2.4vw, 34px); font-weight: 500; letter-spacing: -1px; margin-bottom: 8px; }
.test-overview p:last-child { font-size: 12px; color: var(--muted); margin: 0; }
.test-score { flex-shrink: 0; display: grid; grid-template-columns: 1fr 1fr; gap: 10px 24px; }
.test-score strong { font: 17px ui-monospace, monospace; color: var(--mint); }
.test-score strong span { font-size: 11px; color: var(--muted); }
.test-score > span { grid-column: 1 / -1; font-size: 10px; color: var(--muted); }
[role='tab'] small { font: 10px ui-monospace, monospace; color: #729989; padding: 3px 5px; border: 1px solid #294739; border-radius: 4px; }
.test-question { padding: 14px 16px; margin: 0 0 24px; border-left: 2px solid #708b7e; background: #1b2d35; border-radius: 0 7px 7px 0; }
.test-question p { font-size: 12px; line-height: 1.75; margin: 9px 0 0; color: #bdcbd5; }
.test-question .question-lead { margin-top: 0; color: #eef3ed; }
.observation { padding: 18px 30px; background: #192e31; border-top: 1px solid #2c4947; border-bottom: 1px solid #2c4947; }
.observation .eyebrow { font-size: 9px; }
.observation p { margin: 8px 0 0; font-size: 13px; line-height: 1.75; color: #d1e3df; }
.test-study { padding: 30px 32px; background: #101b26; border-top: 1px solid var(--border); }
.solution-heading { display: flex; align-items: center; justify-content: space-between; gap: 16px; margin-bottom: 22px; }
.solution-heading .eyebrow { margin-bottom: 8px; }
.solution-heading h3 { font-weight: 500; font-size: 23px; margin: 0; letter-spacing: -0.5px; }
.solution-heading a { font-size: 11px; }
.solution details { border: 1px solid #314555; border-radius: 8px; background: #152331; margin: 12px 0; overflow: hidden; }
.solution summary { font-size: 13px; color: #d0e1e8; padding: 17px 20px; line-height: 1.6; }
.solution details[open] summary { color: var(--mint); border-bottom: 1px solid #314555; }
.derivation { margin: 0; padding: 8px 24px 20px 52px; counter-reset: step; }
.derivation li { padding: 8px 0 0 6px; color: var(--mint); }
.derivation li::marker { font: 13px ui-monospace, monospace; }
.derivation p { font-size: 13px !important; color: #a9becb; line-height: 1.8; margin: 8px 0; }
.derivation .math-step { font-size: 15px !important; color: #edf4ef; background: #0d1924; border-radius: 5px; padding: 12px 14px; }
.prediction { padding: 24px; margin-top: 24px; border: 1px solid #5b5138; border-radius: 8px; background: #262a28; }
.prediction .eyebrow { color: var(--gold, #f5d58b); }
.prediction h3 { font-size: 16px; font-weight: 500; line-height: 1.65; margin: 0 0 16px; }
.prediction button { background: transparent; border: 1px solid #8c805b; border-radius: 5px; color: #f5d58b; padding: 9px 13px; font-size: 12px; }
.prediction > p:last-child { font-size: 13px; color: #d3d6c6; line-height: 1.8; margin: 18px 0 0; }
.lesson-pagination { display: grid; grid-template-columns: 1fr auto 1fr; align-items: center; gap: 10px; margin-top: 30px; }
.lesson-pagination a { font-size: 12px; text-decoration: none; }
.lesson-pagination a:first-child { grid-column: 1; }
.lesson-pagination span { grid-column: 2; font: 11px ui-monospace, monospace; color: var(--muted); }
.lesson-pagination a:last-child { grid-column: 3; text-align: right; }
.math-display { max-width: 100%; min-width: 0; overflow-x: auto; overflow-y: hidden; padding: 6px 2px; scrollbar-width: thin; scrollbar-color: #526e7c transparent; }
.math-display .katex-display { text-align: left; margin: 0.5em 0; }
.math-display .katex-display > .katex { text-align: left; }
.katex { font-size: 1.08em; }
.math-display:focus-visible { outline: 2px solid var(--mint); outline-offset: 3px; }
@media (max-width: 850px) {
  .app-header { flex-wrap: wrap; gap: 16px; }
  .collections { margin-left: auto; }
  .header-title { flex: 1; }
  .test-overview { padding: 25px 22px; gap: 20px; }
  .test-score { gap: 8px 14px; }
}
@media (max-width: 600px) {
  .app-header { padding: 16px 20px; }
  .collections { width: 100%; margin: 0; flex-wrap: wrap; }
  .collections a { flex: 1; text-align: center; }
  .language-picker { flex: 1 0 100%; margin: 4px 0 0; padding: 8px 4px 4px; border-left: 0; border-top: 1px solid var(--border); }
  .test-overview { align-items: flex-start; flex-direction: column; gap: 18px; padding: 24px 20px; }
  .test-score { display: flex; align-items: center; flex-wrap: wrap; gap: 16px; }
  .test-score > span { font-size: 9px; }
  .observation { padding: 18px 20px; }
  .test-study { padding: 26px 20px; }
  .solution-heading { align-items: flex-start; flex-direction: column; }
  .derivation { padding-left: 35px; padding-right: 14px; }
  .derivation .math-step { font-size: 13px !important; padding: 10px; }
  .prediction { padding: 19px; }
  .lesson-pagination a { font-size: 11px; }
}
details p { font-size: 11px !important; }
.webgl-error { position: absolute; z-index: 2; top: 140px; left: 12%; right: 12%; padding: 24px; background: #1e2937; border: 1px solid #ff967b; border-radius: 8px; color: #ffb79f; font-size: 14px; line-height: 1.7; }
@media (min-width: 1600px) { main { grid-template-columns: 340px minmax(0, 1fr); } .controls-panel { padding: 32px; } }
@media (max-width: 1100px) { .app-header { padding: 16px 24px; } .subjects { padding: 0 12px; } [role='tab'] { padding: 18px 12px; } main { grid-template-columns: 280px minmax(0, 1fr); } .controls-panel { padding: 24px 20px; } .learning-panel { grid-template-columns: 1fr; gap: 24px; padding: 25px; } .challenge { border-left: 0; border-top: 1px solid var(--border); padding: 22px 0 0; } }
@media (max-width: 760px) {
  .app-header { padding: 16px; gap: 13px; min-height: 88px; }
  .brand { font-size: 15px; padding: 12px 8px; }
  h1 { font-size: 15px; }
  .header-title p { font-size: 10px; }
  .status { display: none; }
  main { display: flex; flex-direction: column; }
  .controls-panel { border-right: 0; border-bottom: 1px solid var(--border); padding: 24px; }
  h2 { font-size: 25px; }
  #parameters { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0 24px; }
  .parameter { min-width: 0; margin: 10px 0 15px; }
  .parameter-label { flex-wrap: wrap; gap: 6px; }
  .measurements { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0 16px; margin-top: 18px; }
  .measurement { min-width: 0; }
  .measurement strong { font-size: 21px; overflow-wrap: anywhere; }
  .measurement > div { flex-wrap: wrap; gap: 4px; }
  .measurement:nth-child(2) { border-top: 0; }
  #viewport { height: 520px; }
  .scene-toolbar { top: 18px; left: 16px; right: 16px; }
  .scene-toolbar button { font-size: 10px; padding: 7px; }
  .legend { left: 16px; right: 16px; }
  .scene-footer { padding: 20px 16px 12px; }
  .learning-panel { padding: 24px; }
}