:root {
  --page-bg: #f6f4ef;
  --page-top: #fcfbf8;
  --page-glow: rgba(255, 255, 255, 0.95);
  --panel-bg: #ffffff;
  --panel-bg-soft: #faf8f2;
  --panel-bg-alt: #f7faf9;
  --surface-soft: #f8f9fb;
  --panel-edge: rgba(15, 23, 42, 0.08);
  --panel-shadow: 0 20px 45px rgba(15, 23, 42, 0.12);
  --text-main: #1f2937;
  --text-soft: #5f6b7a;
  --text-strong-soft: #362e2e;
  --accent: #0f766e;
  --accent-strong: #115e59;
  --input-bg: #fbfbf8;
  --toggle-bg: rgba(255, 255, 255, 0.72);
  --toggle-border: rgba(15, 23, 42, 0.12);
  --diagram-bg: #ffffff;
  --diagram-text: #0f172a;
  --diagram-heading: #334155;
  --grid-gap: 1.25rem;
  --radius: 20px;
  color-scheme: light;
}

:root[data-theme='dark'] {
  --page-bg: #0f172a;
  --page-top: #162033;
  --page-glow: rgba(22, 32, 51, 0.72);
  --panel-bg: #111827;
  --panel-bg-soft: #162033;
  --panel-bg-alt: #12202a;
  --surface-soft: #182334;
  --panel-edge: rgba(148, 163, 184, 0.16);
  --panel-shadow: 0 24px 50px rgba(2, 6, 23, 0.42);
  --text-main: #e5eef8;
  --text-soft: #9fb1c7;
  --text-strong-soft: #c9d6e3;
  --input-bg: #0b1220;
  --toggle-bg: rgba(15, 23, 42, 0.6);
  --toggle-border: rgba(148, 163, 184, 0.2);
  --diagram-bg: #0b1220;
  --diagram-text: #e5eef8;
  --diagram-heading: #a8b7ca;
  color-scheme: dark;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: Georgia, 'Avenir Next', 'Segoe UI', sans-serif;
  color: var(--text-main);
  background:
    radial-gradient(circle at top left, var(--page-glow), transparent 35%),
    linear-gradient(180deg, var(--page-top) 0%, var(--page-bg) 100%);
  transition: background-color 180ms ease, color 180ms ease;
}

:root[data-theme='light'] body,
:root:not([data-theme]) body {
  color: #1f2937;
}

:root[data-theme='dark'] body {
  color: #e5eef8;
}

button,
input,
textarea {
  font: inherit;
}

button {
  cursor: pointer;
}

.app-shell {
  width: min(1200px, calc(100% - 2rem));
  margin: 0 auto;
  padding: 2.5rem 0 3rem;
}

.hero {
  max-width: none;
  margin-bottom: 1.75rem;
}

.hero > :not(.title-row) {
  max-width: 760px;
}

.title-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  gap: 1rem;
}

.eyebrow {
  margin: 0 0 0.4rem;
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
}

.hero h1 {
  margin: 0;
  font-size: clamp(2.25rem, 4vw, 3.4rem);
  line-height: 1;
}

.hero-credit {
  margin: 0.7rem 0 0;
  color: var(--text-strong-soft);
  font-size: 0.95rem;
}

.hero-credit a {
  color: inherit;
}

.theme-toggle {
  border: 1px solid var(--toggle-border);
  border-radius: 999px;
  padding: 0.72rem 1rem;
  background: var(--toggle-bg);
  color: var(--text-main);
  font-weight: 700;
  transition: transform 150ms ease, background-color 150ms ease, border-color 150ms ease;
}

.theme-toggle:hover {
  transform: translateY(-1px);
}

.intro {
  margin: 0.9rem 0 0;
  max-width: 60ch;
  color: var(--text-soft);
  font-size: 1.02rem;
  line-height: 1.6;
}

.workspace {
  display: flex;
  flex-wrap: wrap;
  gap: 1.5rem;
  align-items: flex-start;
}

.controls,
.diagram-panel {
  background: var(--panel-bg);
  border: 1px solid var(--panel-edge);
  border-radius: var(--radius);
  box-shadow: var(--panel-shadow);
}

.controls {
  flex: 1 1 360px;
  padding: 1.35rem;
}

.controls-header {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: flex-start;
  margin-bottom: 1.2rem;
}

.controls-header h2,
.diagram-head h2 {
  margin: 0;
  font-size: 1.2rem;
}

.mode-switch {
  display: inline-flex;
  gap: 0.5rem;
  margin: 0;
  padding: 0.35rem;
  border: 1px solid rgba(15, 118, 110, 0.18);
  border-radius: 999px;
  background: color-mix(in srgb, var(--panel-bg) 70%, var(--accent) 8%);
}

.mode-switch legend {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.mode-option {
  position: relative;
  display: inline-flex;
  align-items: center;
}

.mode-option input {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}

.mode-option span {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 5.25rem;
  padding: 0.6rem 1rem;
  border-radius: 999px;
  font-weight: 700;
  color: var(--text-soft);
  transition: background-color 150ms ease, color 150ms ease, transform 150ms ease;
}

.mode-option input:checked + span {
  background: var(--accent);
  color: #ffffff;
  transform: translateY(-1px);
}

.input-grid {
  display: flex;
  flex-wrap: wrap;
  gap: var(--grid-gap);
}

.set-card {
  flex: 1 1 220px;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  padding: 1rem;
  border-radius: 16px;
  background: linear-gradient(180deg, var(--panel-bg) 0%, var(--panel-bg-soft) 100%);
  border: 1px solid rgba(15, 23, 42, 0.06);
}

.set-card.is-hidden {
  display: none;
}

.geometry-panel,
.data-panel {
  margin-top: 1.2rem;
  padding: 1rem;
  border-radius: 16px;
  background: linear-gradient(180deg, var(--panel-bg) 0%, var(--panel-bg-alt) 100%);
  border: 1px solid rgba(15, 23, 42, 0.06);
}

.section-head {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: baseline;
  margin-bottom: 0.85rem;
}

.section-head h3 {
  margin: 0;
  font-size: 1rem;
}

.section-head p {
  margin: 0;
  color: var(--text-soft);
  font-size: 0.94rem;
}

.geometry-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(190px, 1fr));
  gap: 0.9rem;
}

.geometry-card {
  padding: 0.9rem;
  border-radius: 14px;
  background: color-mix(in srgb, var(--panel-bg) 86%, transparent);
  border: 1px solid rgba(15, 23, 42, 0.08);
}

.geometry-card h4 {
  margin: 0 0 0.75rem;
  font-size: 0.98rem;
}

.geometry-fields {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.6rem;
}

.field-stack {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.field-stack label {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--text-soft);
}

.field-stack input {
  min-height: 2.45rem;
  padding: 0.55rem 0.65rem;
}

.json-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.json-actions button {
  border: 0;
  border-radius: 999px;
  padding: 0.78rem 1.1rem;
  font-weight: 700;
  background: color-mix(in srgb, var(--panel-bg) 65%, var(--accent) 10%);
  color: var(--accent-strong);
}

label {
  font-weight: 700;
}

input,
textarea {
  width: 100%;
  border: 1px solid rgba(15, 23, 42, 0.15);
  border-radius: 12px;
  background: var(--input-bg);
  color: var(--text-main);
}

input {
  min-height: 2.8rem;
  padding: 0.7rem 0.85rem;
}

textarea {
  min-height: 8.5rem;
  padding: 0.8rem 0.85rem;
  resize: vertical;
  line-height: 1.5;
}

input:focus,
textarea:focus,
button:focus-visible {
  outline: 3px solid rgba(15, 118, 110, 0.18);
  outline-offset: 2px;
}

.action-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 1.2rem;
}

.action-row button {
  border: 0;
  border-radius: 999px;
  padding: 0.9rem 1.25rem;
  font-weight: 700;
  transition: transform 150ms ease, box-shadow 150ms ease, background-color 150ms ease;
}

#generate-btn {
  background: var(--accent);
  color: #ffffff;
}

#export-svg-btn,
#export-png-btn {
  background: color-mix(in srgb, var(--panel-bg) 65%, var(--accent) 10%);
  color: var(--accent-strong);
}

.action-row button:hover {
  transform: translateY(-1px);
  box-shadow: 0 10px 20px rgba(15, 118, 110, 0.12);
}

.diagram-panel {
  flex: 1 1 520px;
  padding: 1.2rem;
  min-height: 660px;
}

.diagram-head {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: baseline;
  margin-bottom: 0.9rem;
}

.diagram-head p {
  margin: 0;
  color: var(--text-soft);
}

#diagram-container {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 580px;
  padding: 1rem;
  border-radius: 18px;
  background: linear-gradient(180deg, var(--panel-bg) 0%, var(--surface-soft) 100%);
  box-shadow: inset 0 0 0 1px rgba(15, 23, 42, 0.06);
}

#diagram-container svg {
  width: 100%;
  height: auto;
  max-height: 100%;
  display: block;
}

.equation-panel {
  margin-top: 1rem;
  padding: 1rem;
  border-radius: 18px;
  background: linear-gradient(180deg, var(--panel-bg) 0%, var(--panel-bg-alt) 100%);
  border: 1px solid rgba(15, 23, 42, 0.06);
}

#equation-container {
  display: grid;
  gap: 0.75rem;
}

.equation-card {
  padding: 0.9rem 1rem;
  border-radius: 14px;
  background: color-mix(in srgb, var(--panel-bg) 86%, transparent);
  border: 1px solid rgba(15, 23, 42, 0.08);
}

.equation-expression,
.equation-caption {
  margin: 0;
}

.equation-expression {
  font-size: 0.98rem;
  font-weight: 700;
  line-height: 1.5;
  color: var(--text-main);
  overflow-wrap: anywhere;
}

.equation-caption {
  margin-top: 0.35rem;
  color: var(--text-soft);
  font-size: 0.9rem;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (max-width: 840px) {
  .app-shell {
    width: min(100% - 1.2rem, 1000px);
    padding-top: 1.2rem;
  }

  .title-row {
    flex-direction: column;
    align-items: flex-start;
  }

  .controls-header,
  .diagram-head,
  .section-head {
    flex-direction: column;
    align-items: stretch;
  }

  .mode-switch {
    align-self: flex-start;
  }

  .diagram-panel {
    min-height: 0;
  }

  #diagram-container {
    min-height: 420px;
    padding: 0.5rem;
  }
}