:root {
  color-scheme: light;
  --accent: #205493;
  --accent-dark: #153a67;
  --accent-soft: #e7f0fb;
  --ink: #172033;
  --muted: #536075;
  --line: #c8d2e1;
  --panel: #ffffff;
  --canvas: #f4f7fb;
  --success: #176b3a;
  --success-bg: #e6f6ec;
  --error: #9b2226;
  --error-bg: #fff0f0;
  --warning: #7a4b00;
  --warning-bg: #fff5d9;
  --focus: #ffbf47;
  font-family: Inter, Aptos, "Segoe UI", Arial, sans-serif;
}

* { box-sizing: border-box; }
html { min-width: 0; background: var(--canvas); }
body { margin: 0; min-width: 0; color: var(--ink); background: var(--canvas); font-size: 16px; line-height: 1.45; }
button, input, math-field { font: inherit; }
button { touch-action: manipulation; }
button:focus-visible, input:focus-visible, math-field:focus-within, summary:focus-visible, [tabindex]:focus-visible {
  outline: 4px solid var(--focus);
  outline-offset: 2px;
}

.skip-link { position: fixed; left: 8px; top: -80px; z-index: 100; padding: 10px 14px; color: #fff; background: #111; border-radius: 6px; }
.skip-link:focus { top: 8px; }
.sr-only { position: absolute !important; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }

.app-shell { width: min(100%, 1180px); min-height: 100vh; margin: 0 auto; background: var(--panel); box-shadow: 0 10px 35px rgba(29,45,72,.10); }
.topbar { min-height: 52px; display: flex; align-items: center; gap: 10px; padding: 6px 12px; color: #fff; background: linear-gradient(110deg, var(--accent-dark), var(--accent)); }
.identity { min-width: 0; display: flex; flex: 1; align-items: center; gap: 10px; }
.lo-chip { flex: 0 0 auto; padding: 4px 9px; border: 1px solid rgba(255,255,255,.6); border-radius: 999px; font-size: .78rem; font-weight: 800; letter-spacing: .04em; }
.stage-name { overflow: hidden; font-weight: 700; text-overflow: ellipsis; white-space: nowrap; }
.top-actions { display: flex; gap: 8px; }
.icon-btn { width: 44px; min-width: 44px; height: 44px; border: 1px solid rgba(255,255,255,.7); border-radius: 11px; color: #fff; background: rgba(255,255,255,.12); font-weight: 800; cursor: pointer; }
.icon-btn:active { transform: scale(.97); background: rgba(255,255,255,.25); }

.learning-stage { padding: 10px; }
.prompt-card { display: grid; grid-template-columns: minmax(0,1fr) minmax(120px,170px); align-items: center; gap: 12px; padding: 10px 12px; border: 1px solid var(--line); border-left: 5px solid var(--accent); border-radius: 12px; background: #fff; }
.prompt-copy { min-width: 0; }
.level-pill { display: inline-block; margin-bottom: 2px; color: var(--accent-dark); font-size: .76rem; font-weight: 850; letter-spacing: .06em; text-transform: uppercase; }
h1 { margin: 0; font-size: clamp(1.05rem, 2vw, 1.35rem); line-height: 1.25; }
#instructionText { margin: 3px 0 0; color: var(--muted); font-size: .94rem; }
.progress-copy { font-size: .82rem; color: var(--muted); text-align: right; }
.progress-track { height: 8px; margin-top: 5px; overflow: hidden; border-radius: 999px; background: #e7ebf2; }
.progress-track span { display: block; width: 0; height: 100%; border-radius: inherit; background: var(--accent); transition: width .25s ease; }

.workspace { display: grid; grid-template-columns: minmax(0,1.22fr) minmax(280px,.78fr); gap: 10px; margin-top: 10px; }
.model-panel, .response-panel { min-width: 0; border: 1px solid var(--line); border-radius: 12px; background: #fff; overflow: hidden; }
.panel-label { padding: 6px 10px; color: #35445d; background: #edf2f8; font-size: .78rem; font-weight: 800; letter-spacing: .03em; text-transform: uppercase; }
.model-host { min-height: 210px; display: grid; place-items: center; padding: 6px; background: linear-gradient(#fff, #f8fbff); }
.model-host svg { width: 100%; max-width: 580px; height: 210px; display: block; }
.model-host .formula-model { width: 100%; padding: 14px; text-align: center; }
.formula-main { margin-bottom: 12px; font-family: Cambria, "Times New Roman", serif; font-size: clamp(1.3rem,4vw,2rem); font-weight: 700; }
.component-row { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.component-card { padding: 12px; border-radius: 10px; background: var(--accent-soft); border: 1px solid color-mix(in srgb, var(--accent) 35%, white); }
.component-card strong { display: block; color: var(--accent-dark); font-size: .78rem; text-transform: uppercase; }
.legend { min-height: 28px; padding: 4px 10px 7px; color: var(--muted); font-size: .82rem; text-align: center; }
.legend-key { display: inline-flex; align-items: center; gap: 5px; margin: 0 7px; }
.legend-swatch { width: 12px; height: 12px; border-radius: 50%; display: inline-block; }

.response-panel { display: flex; flex-direction: column; }
.response-host { min-height: 146px; display: grid; align-content: center; gap: 8px; padding: 10px; }
.choice-grid { display: grid; grid-template-columns: 1fr; gap: 7px; }
.choice-btn { min-height: 44px; padding: 8px 10px; border: 2px solid var(--line); border-radius: 9px; color: var(--ink); background: #fff; text-align: left; cursor: pointer; }
.choice-btn[aria-pressed="true"] { border-color: var(--accent); background: var(--accent-soft); box-shadow: inset 4px 0 var(--accent); }
.choice-btn:active { transform: scale(.99); }
.input-grid { display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); gap: 10px; }
.input-grid.four { grid-template-columns: repeat(4,minmax(0,1fr)); }
.math-input label { display: block; margin-bottom: 4px; color: var(--muted); font-size: .82rem; font-weight: 700; }
.math-input math-field { width: 100%; min-width: 0; min-height: 52px; padding: 7px 9px; border: 2px solid var(--line); border-radius: 9px; background: #fff; font-size: 1.2rem; text-align: center; --caret-color: var(--accent); --selection-background-color: var(--accent-soft); }
.math-input math-field:focus-within { border-color: var(--accent); box-shadow: 0 0 0 2px color-mix(in srgb,var(--accent) 22%,transparent); }
.math-input math-field[aria-invalid="true"] { border-color: var(--error); background: var(--error-bg); }
.math-input math-field[read-only] { color: var(--ink); background: #f2f5f9; }
.math-input-help { grid-column: 1 / -1; margin: 0; color: var(--muted); font-size: .8rem; line-height: 1.35; }
.number-wrap { max-width: 260px; margin: 0 auto; }
.point-readout { display: flex; justify-content: center; gap: 8px; padding: 8px; color: var(--accent-dark); background: var(--accent-soft); border-radius: 9px; font-weight: 800; }
.feedback { min-height: 56px; display: flex; align-items: center; gap: 9px; margin: auto 10px 10px; padding: 8px 10px; border: 1px solid var(--line); border-radius: 9px; color: var(--muted); background: #f8fafc; font-size: .9rem; }
.feedback.correct { color: var(--success); background: var(--success-bg); border-color: #6fb889; }
.feedback.incorrect { color: var(--error); background: var(--error-bg); border-color: #e69a9d; }
.feedback.hint { color: var(--warning); background: var(--warning-bg); border-color: #d8b866; }
.feedback-icon { flex: 0 0 auto; font-size: 1.2rem; font-weight: 900; }

.actionbar { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 10px; }
.btn { min-height: 44px; padding: 8px 13px; border: 2px solid transparent; border-radius: 9px; font-weight: 800; cursor: pointer; }
.btn:disabled { cursor: not-allowed; opacity: .48; }
.btn.primary { color: #fff; background: var(--accent); }
.btn.next { color: #fff; background: #176b3a; }
.btn.secondary { color: var(--accent-dark); border-color: var(--line); background: #fff; }
.btn.compact { min-height: 44px; padding: 6px 10px; }
.btn:not(:disabled):active { transform: scale(.98); }
.stage-dots { display: flex; justify-content: center; gap: 8px; padding: 9px 0 3px; }
.stage-dot { width: 30px; height: 8px; border: 0; border-radius: 999px; background: #d8dfeb; }
.stage-dot.current { background: var(--accent); }
.stage-dot.complete { background: var(--success); }

.analytics { margin-top: 8px; border-top: 1px solid var(--line); }
.analytics summary { min-height: 44px; display: flex; align-items: center; justify-content: space-between; gap: 12px; padding: 7px 4px; color: var(--accent-dark); font-weight: 800; cursor: pointer; }
.analytics-body { padding: 4px 8px 12px; border-radius: 10px; background: #f5f8fc; }
.analytics-body p { margin: 4px 0 8px; }
.analytics-body ol { max-height: 150px; margin: 0 0 8px; padding-left: 24px; overflow: auto; }
.analytics-body li { margin: 4px 0; font-size: .86rem; }

.dialog-backdrop { position: fixed; inset: 0; z-index: 50; display: grid; place-items: center; padding: 14px; background: rgba(18,27,43,.68); }
.dialog-backdrop[hidden] { display: none; }
.dialog { position: relative; width: min(700px,100%); max-height: min(86vh,760px); overflow: auto; padding: 20px; border-radius: 15px; background: #fff; box-shadow: 0 25px 65px rgba(0,0,0,.3); }
.dialog h2 { margin: 0 44px 10px 0; font-size: 1.35rem; }
.dialog p { margin: 7px 0; }
.dialog-close { position: absolute; right: 10px; top: 10px; width: 44px; height: 44px; border: 1px solid var(--line); border-radius: 10px; color: var(--ink); background: #fff; font-size: 1.6rem; cursor: pointer; }
.speech-controls { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 14px; border: 1px solid var(--line); border-radius: 10px; }
.speech-controls label { display: grid; grid-template-columns: auto 1fr auto; align-items: center; gap: 8px; min-height: 44px; }
.speech-controls input { width: 100%; }
.eyebrow { color: var(--accent-dark); font-size: .78rem; font-weight: 850; letter-spacing: .06em; text-transform: uppercase; }
.tutorial-attempt { padding: 10px; border-left: 4px solid var(--error); border-radius: 8px; background: var(--error-bg); }
.tutorial-visual { min-height: 120px; display: grid; place-items: center; margin: 10px 0; padding: 12px; border: 1px solid var(--line); border-radius: 10px; background: linear-gradient(135deg,var(--accent-soft),#fff); text-align: center; }
.tutorial-visual .phase-symbol { font-family: Cambria, "Times New Roman", serif; font-size: clamp(1.4rem,5vw,2.3rem); font-weight: 700; }
.tutorial-steps { margin: 8px 0; padding-left: 25px; }
.tutorial-steps li { display: none; margin: 5px 0; }
.tutorial-steps li.revealed { display: list-item; }
.tutorial-steps li.active { color: var(--accent-dark); font-weight: 800; }
.tutorial-controls { display: grid; grid-template-columns: auto 1fr auto; align-items: center; gap: 10px; }
#tutorialProgress { text-align: center; font-weight: 700; }

.argand-grid .grid-line { stroke: #e1e6ef; stroke-width: 1; }
.argand-grid .axis { stroke: #28364c; stroke-width: 2; }
.argand-grid .tick-label { fill: #536075; font-size: 11px; }
.argand-grid .axis-label { fill: #172033; font-size: 13px; font-weight: 800; }
.argand-grid .given { fill: var(--accent); stroke: #fff; stroke-width: 2; }
.argand-grid .secondary-point { fill: #c45a00; stroke: #fff; stroke-width: 2; }
.argand-grid .target { fill: #fff; stroke: #9b2226; stroke-width: 3; cursor: crosshair; }
.argand-grid .vector { stroke: var(--accent); stroke-width: 3; fill: none; }
.argand-grid .secondary-vector { stroke: #c45a00; stroke-width: 3; fill: none; }
.argand-grid .guide { stroke: #7b8799; stroke-width: 1.5; stroke-dasharray: 5 4; fill: none; }
.argand-grid .angle-arc { stroke: #7a4b00; stroke-width: 3; fill: none; }
.set-map { width: 100%; min-height: 190px; position: relative; display: grid; place-items: center; }
.set-ring { position: absolute; display: grid; place-items: start center; padding-top: 8px; border: 3px solid var(--accent); border-radius: 50%; color: var(--accent-dark); font-size: .78rem; font-weight: 800; background: color-mix(in srgb,var(--accent-soft) 55%,transparent); }
.set-ring.complex { width: 88%; height: 178px; }
.set-ring.real { width: 65%; height: 135px; top: 28px; }
.set-ring.integer { width: 40%; height: 92px; top: 60px; }
.set-focus { position: relative; z-index: 2; padding: 9px 13px; border-radius: 9px; color: #fff; background: var(--accent-dark); font-family: Cambria,serif; font-size: 1.25rem; font-weight: 800; }

@media (max-width: 760px) {
  .workspace { grid-template-columns: 1fr; }
  .model-host { min-height: 190px; }
  .model-host svg { height: 190px; }
  .response-host { min-height: auto; }
  .input-grid.four { grid-template-columns: repeat(2,minmax(0,1fr)); }
  .actionbar .btn { flex: 1 1 calc(33.3% - 8px); }
}

@media (max-width: 430px) {
  body { font-size: 15px; }
  .learning-stage { padding: 7px; }
  .topbar { padding-inline: 7px; }
  .stage-name { font-size: .88rem; }
  .prompt-card { grid-template-columns: 1fr; gap: 5px; }
  .progress-copy { text-align: left; }
  .model-host { min-height: 145px; padding: 2px; }
  .model-host svg { height: 145px; }
  .choice-grid.two-column { grid-template-columns: repeat(2,minmax(0,1fr)); }
  .choice-btn { padding: 6px 8px; font-size: .88rem; }
  .actionbar { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); }
  .actionbar .btn { min-width: 0; padding-inline: 6px; font-size: .84rem; }
  .set-map { min-height: 142px; }
  .set-ring.complex { height: 136px; }
  .set-ring.real { height: 103px; top: 22px; }
  .set-ring.integer { height: 70px; top: 49px; }
  .speech-controls { grid-template-columns: 1fr; }
  .dialog { padding: 16px; }
  .tutorial-controls { grid-template-columns: 1fr 1fr; }
  #tutorialProgress { grid-column: 1 / -1; grid-row: 1; }
}

@media (hover: none) and (pointer: coarse) {
  .btn, .choice-btn, .icon-btn { min-height: 44px; }
  .icon-btn { height: 44px; }
  .choice-grid { gap: 9px; }
}

@media (min-width: 1024px) {
  .btn, .choice-btn, .icon-btn { min-height: 48px; }
  .btn.compact { min-height: 48px; }
  .icon-btn { height: 48px; }
  .choice-grid { gap: 10px; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition-duration: .01ms !important; animation-duration: .01ms !important; animation-iteration-count: 1 !important; }
}

@media (forced-colors: active) {
  .btn, .choice-btn, .model-panel, .response-panel, .prompt-card { border: 2px solid ButtonText; }
  .stage-dot.current, .stage-dot.complete { forced-color-adjust: none; background: Highlight; }
}