/* ============================================================
   ORBITAL MECHANICS SIMULATOR — Design Tokens
   Concept: mission-control / observatory data console.
   Dark space background by default, deep-space navy + starfield,
   amber "truth" accent (gravity), magenta "flaw" accent (density).
   ============================================================ */

:root,
[data-theme='light'] {
  --color-bg: #f4f2ec;
  --color-surface: #fbfaf6;
  --color-surface-2: #ffffff;
  --color-surface-offset: #ece8de;
  --color-surface-offset-2: #e3ded1;
  --color-divider: #d9d3c3;
  --color-border: #c9c2ac;

  --color-text: #1c1a14;
  --color-text-muted: #5c5747;
  --color-text-faint: #9b9480;
  --color-text-inverse: #f8f6ef;

  --color-primary: #b8791f;      /* amber — gravity / truth */
  --color-primary-hover: #a06318;
  --color-primary-active: #7d4e12;
  --color-primary-highlight: #ecd9b3;

  --color-flaw: #ac2f6b;         /* magenta — density / flawed model */
  --color-flaw-hover: #8c2557;
  --color-flaw-highlight: #ecc9dc;

  --color-accent-2: #1b7c8c;     /* teal — secondary data series */
  --color-success: #3f7a3a;
  --color-warning: #a35a12;
  --color-error: #ac2f2f;

  --radius-sm: 0.375rem;
  --radius-md: 0.625rem;
  --radius-lg: 1rem;
  --radius-xl: 1.5rem;
  --radius-full: 9999px;

  --transition-interactive: 180ms cubic-bezier(0.16, 1, 0.3, 1);

  --shadow-sm: 0 1px 2px oklch(0.2 0.02 80 / 0.08);
  --shadow-md: 0 6px 20px oklch(0.2 0.02 80 / 0.12);
  --shadow-lg: 0 20px 48px oklch(0.15 0.02 80 / 0.22);

  --content-narrow: 640px;
  --content-default: 1080px;
  --content-wide: 1320px;

  --font-display: 'General Sans', 'Segoe UI', sans-serif;
  --font-body: 'General Sans', 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Courier New', monospace;

  color-scheme: light;
}

[data-theme='dark'] {
  --color-bg: #0a0d16;
  --color-surface: #10141f;
  --color-surface-2: #141828;
  --color-surface-offset: #171c2c;
  --color-surface-offset-2: #1c2233;
  --color-divider: #232a3d;
  --color-border: #2b3348;

  --color-text: #e7e6ec;
  --color-text-muted: #979db3;
  --color-text-faint: #5c6280;
  --color-text-inverse: #0a0d16;

  --color-primary: #f0b04a;
  --color-primary-hover: #f7c26b;
  --color-primary-active: #ffd58a;
  --color-primary-highlight: #3a3020;

  --color-flaw: #ec5aa0;
  --color-flaw-hover: #f37cb5;
  --color-flaw-highlight: #3a2233;

  --color-accent-2: #4fd0e0;
  --color-success: #6fbf5f;
  --color-warning: #f0a04a;
  --color-error: #ec6a6a;

  --shadow-sm: 0 1px 2px oklch(0 0 0 / 0.4);
  --shadow-md: 0 6px 20px oklch(0 0 0 / 0.45);
  --shadow-lg: 0 24px 56px oklch(0 0 0 / 0.55);

  color-scheme: dark;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --color-bg: #0a0d16;
    --color-surface: #10141f;
    --color-surface-2: #141828;
    --color-surface-offset: #171c2c;
    --color-surface-offset-2: #1c2233;
    --color-divider: #232a3d;
    --color-border: #2b3348;
    --color-text: #e7e6ec;
    --color-text-muted: #979db3;
    --color-text-faint: #5c6280;
    --color-text-inverse: #0a0d16;
    --color-primary: #f0b04a;
    --color-primary-hover: #f7c26b;
    --color-primary-active: #ffd58a;
    --color-primary-highlight: #3a3020;
    --color-flaw: #ec5aa0;
    --color-flaw-hover: #f37cb5;
    --color-flaw-highlight: #3a2233;
    --color-accent-2: #4fd0e0;
    color-scheme: dark;
  }
}

/* Fluid type scale */
:root {
  --text-xs: clamp(0.75rem, 0.72rem + 0.15vw, 0.8125rem);
  --text-sm: clamp(0.875rem, 0.83rem + 0.2vw, 0.9375rem);
  --text-base: clamp(1rem, 0.96rem + 0.2vw, 1.0625rem);
  --text-lg: clamp(1.125rem, 1.05rem + 0.4vw, 1.375rem);
  --text-xl: clamp(1.375rem, 1.15rem + 1vw, 1.875rem);
  --text-2xl: clamp(1.875rem, 1.3rem + 2.2vw, 2.75rem);
  --text-hero: clamp(2.25rem, 1.3rem + 3.4vw, 3.75rem);

  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;
}

/* ============================================================
   BASE
   ============================================================ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  scroll-behavior: smooth;
  scroll-padding-top: 5rem;
}

body {
  min-height: 100dvh;
  line-height: 1.6;
  font-family: var(--font-body);
  font-size: var(--text-base);
  color: var(--color-text);
  background-color: var(--color-bg);
  position: relative;
}

img, canvas, svg { display: block; max-width: 100%; }
p, li { max-width: 68ch; }

h1, h2, h3, h4 { text-wrap: balance; line-height: 1.15; font-family: var(--font-display); }

a { color: var(--color-primary); text-decoration: none; }
a:hover { text-decoration: underline; }

::selection { background: color-mix(in oklab, var(--color-primary) 30%, transparent); }

:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

button { cursor: pointer; background: none; border: none; font: inherit; color: inherit; }
input, select { font: inherit; color: inherit; }
table { border-collapse: collapse; width: 100%; }

.font-mono { font-family: var(--font-mono); }

/* ============================================================
   STARFIELD BACKDROP
   ============================================================ */
.starfield {
  position: fixed;
  inset: 0;
  z-index: -1;
  background: radial-gradient(ellipse at 20% -10%, color-mix(in oklab, var(--color-primary) 10%, transparent), transparent 55%),
              radial-gradient(ellipse at 90% 10%, color-mix(in oklab, var(--color-accent-2) 8%, transparent), transparent 50%),
              var(--color-bg);
}
[data-theme='dark'] .starfield::before,
:root:not([data-theme]) .starfield::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    radial-gradient(1.5px 1.5px at 8% 12%, #fff 100%, transparent),
    radial-gradient(1px 1px at 22% 38%, #fff 100%, transparent),
    radial-gradient(1.2px 1.2px at 35% 8%, #fff 100%, transparent),
    radial-gradient(1px 1px at 48% 62%, #fff 100%, transparent),
    radial-gradient(1.5px 1.5px at 62% 22%, #fff 100%, transparent),
    radial-gradient(1px 1px at 75% 48%, #fff 100%, transparent),
    radial-gradient(1.3px 1.3px at 88% 15%, #fff 100%, transparent),
    radial-gradient(1px 1px at 92% 70%, #fff 100%, transparent),
    radial-gradient(1.4px 1.4px at 15% 82%, #fff 100%, transparent),
    radial-gradient(1px 1px at 55% 90%, #fff 100%, transparent),
    radial-gradient(1.2px 1.2px at 70% 85%, #fff 100%, transparent),
    radial-gradient(1px 1px at 30% 55%, #fff 100%, transparent);
  opacity: 0.5;
}

/* ============================================================
   HEADER
   ============================================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  backdrop-filter: blur(10px);
  background: color-mix(in oklab, var(--color-bg) 78%, transparent);
  border-bottom: 1px solid var(--color-divider);
}
.header-inner {
  max-width: var(--content-wide);
  margin-inline: auto;
  padding: var(--space-4) var(--space-6);
  display: flex;
  align-items: center;
  gap: var(--space-8);
}
.logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-family: var(--font-mono);
  font-weight: 600;
  font-size: var(--text-sm);
  color: var(--color-text);
  letter-spacing: 0.01em;
  margin-right: auto;
}
.logo:hover { text-decoration: none; color: var(--color-primary); }
.logo svg { color: var(--color-primary); }

.back-link {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-text-faint);
  text-decoration: none;
  padding-right: var(--space-4);
  border-right: 1px solid var(--color-divider);
  margin-right: var(--space-2);
  transition: color var(--transition-interactive);
  white-space: nowrap;
}
.back-link:hover { color: var(--color-primary); }
@media (max-width: 640px) {
  .back-link { display: none; }
}

.header-nav { display: flex; gap: var(--space-6); }
.header-nav a {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  white-space: nowrap;
}
.header-nav a:hover { color: var(--color-text); text-decoration: none; }

.theme-toggle {
  width: 2.25rem; height: 2.25rem;
  display: grid; place-items: center;
  border-radius: var(--radius-full);
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
  flex-shrink: 0;
}
.theme-toggle:hover { color: var(--color-primary); border-color: var(--color-primary); }

@media (max-width: 800px) {
  .header-nav { display: none; }
}

/* ============================================================
   HERO
   ============================================================ */
.hero { padding: clamp(var(--space-16), 10vw, var(--space-24)) var(--space-6) clamp(var(--space-12), 6vw, var(--space-16)); }
.hero-inner { max-width: var(--content-default); margin-inline: auto; }
.eyebrow {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-primary);
  margin-bottom: var(--space-4);
}
.hero h1 {
  font-size: var(--text-hero);
  font-weight: 600;
  max-width: 18ch;
  margin-bottom: var(--space-6);
}
.hero-sub {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  max-width: 56ch;
  margin-bottom: var(--space-8);
}
.hero-cta { display: flex; gap: var(--space-4); flex-wrap: wrap; }

/* ============================================================
   BUTTONS
   ============================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: 600;
  transition: background var(--transition-interactive), color var(--transition-interactive), border-color var(--transition-interactive), transform var(--transition-interactive);
}
.btn-primary { background: var(--color-primary); color: var(--color-text-inverse); }
.btn-primary:hover { background: var(--color-primary-hover); text-decoration: none; transform: translateY(-1px); }
.btn-ghost { border: 1px solid var(--color-border); color: var(--color-text); }
.btn-ghost:hover { border-color: var(--color-primary); color: var(--color-primary); text-decoration: none; }
.btn-sm { padding: var(--space-2) var(--space-4); font-size: var(--text-xs); }

/* ============================================================
   SECTION SCAFFOLDING
   ============================================================ */
main > section {
  max-width: var(--content-wide);
  margin-inline: auto;
  padding: clamp(var(--space-12), 6vw, var(--space-20)) var(--space-6);
}
.section-head { max-width: 72ch; margin-bottom: var(--space-10); }
.section-head h2 { font-size: var(--text-2xl); font-weight: 600; margin-bottom: var(--space-4); }
.section-sub { color: var(--color-text-muted); font-size: var(--text-base); }

/* ============================================================
   SIMULATOR
   ============================================================ */
.sim-layout {
  display: grid;
  grid-template-columns: minmax(0, 1.6fr) minmax(280px, 0.9fr);
  gap: var(--space-8);
  align-items: start;
}
@media (max-width: 900px) {
  .sim-layout { grid-template-columns: 1fr; }
}

.sim-canvas-wrap {
  background: var(--color-surface);
  border: 1px solid var(--color-divider);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
  box-shadow: var(--shadow-md);
}

.model-toggle-bar {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  flex-wrap: wrap;
  margin-bottom: var(--space-4);
}
.model-toggle-label {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-text-faint);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}
.model-toggle {
  display: inline-flex;
  background: var(--color-surface-offset);
  border-radius: var(--radius-full);
  padding: 3px;
  gap: 2px;
}
.model-btn {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-muted);
}
.model-btn.active { background: var(--color-surface-2); color: var(--color-text); box-shadow: var(--shadow-sm); }
.model-btn:hover:not(.active) { color: var(--color-text); }

.dot { width: 9px; height: 9px; border-radius: 50%; display: inline-block; flex-shrink: 0; }
.dot-gravity { background: var(--color-primary); }
.dot-density { background: var(--color-flaw); }

#orbit-canvas {
  width: 100%;
  aspect-ratio: 900 / 620;
  border-radius: var(--radius-md);
  background: radial-gradient(ellipse at 50% 50%, color-mix(in oklab, var(--color-primary) 4%, var(--color-bg)), var(--color-bg) 70%);
  border: 1px solid var(--color-divider);
}

.canvas-readout {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: var(--space-3);
  margin-top: var(--space-4);
}
@media (max-width: 700px) {
  .canvas-readout { grid-template-columns: repeat(2, 1fr); }
}
.readout-item {
  background: var(--color-surface-offset);
  border-radius: var(--radius-md);
  padding: var(--space-3);
  text-align: center;
}
.readout-label {
  display: block;
  font-size: var(--text-xs);
  color: var(--color-text-faint);
  margin-bottom: var(--space-1);
}
.readout-value {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: 600;
  font-variant-numeric: tabular-nums;
}

.sim-controls-row {
  display: flex;
  align-items: center;
  gap: var(--space-5);
  flex-wrap: wrap;
  margin-top: var(--space-5);
  padding-top: var(--space-5);
  border-top: 1px solid var(--color-divider);
}
.speed-label {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}
.speed-label input { width: 90px; }
.checkbox-label {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}
.checkbox-label input { width: 16px; height: 16px; accent-color: var(--color-primary); }

.sim-controls-panel {
  background: var(--color-surface);
  border: 1px solid var(--color-divider);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  box-shadow: var(--shadow-md);
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}
.control-block { display: flex; flex-direction: column; gap: var(--space-2); }
.control-title {
  font-size: var(--text-sm);
  font-weight: 600;
}
.control-block select {
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  background: var(--color-surface-2);
  color: var(--color-text);
}
.control-block input[type='range'] {
  width: 100%;
  accent-color: var(--color-primary);
  height: 4px;
}
.control-value-row {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  font-size: var(--text-xs);
}
.control-value-row span:first-child {
  font-family: var(--font-mono);
  font-weight: 600;
  color: var(--color-text);
  font-size: var(--text-sm);
}
.control-hint { color: var(--color-text-faint); text-align: right; }

.control-footnote {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  background: var(--color-surface-offset);
  border-radius: var(--radius-md);
  padding: var(--space-4);
  border-left: 3px solid var(--color-primary);
}
.control-footnote strong { color: var(--color-text); }

/* ============================================================
   EXPLAINER
   ============================================================ */
.explainer-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-6);
}
@media (max-width: 800px) { .explainer-grid { grid-template-columns: 1fr; } }

.explainer-card {
  border-radius: var(--radius-lg);
  padding: var(--space-8);
  border: 1px solid var(--color-divider);
  background: var(--color-surface);
}
.explainer-card.grav { border-top: 3px solid var(--color-primary); }
.explainer-card.dens { border-top: 3px solid var(--color-flaw); }
.explainer-card h3 {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-size: var(--text-lg);
  margin-bottom: var(--space-4);
}
.explainer-card p { color: var(--color-text-muted); margin-bottom: var(--space-3); font-size: var(--text-sm); }
.explainer-card p:last-child { margin-bottom: 0; }
.formula {
  font-family: var(--font-mono);
  font-size: var(--text-base) !important;
  font-weight: 600;
  color: var(--color-text) !important;
  background: var(--color-surface-offset);
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-md);
  display: inline-block;
}

/* ============================================================
   CHARTS & TABLES
   ============================================================ */
.chart-wrap {
  background: var(--color-surface);
  border: 1px solid var(--color-divider);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  box-shadow: var(--shadow-md);
  margin-bottom: var(--space-8);
  height: 420px;
  position: relative;
}
.table-wrap {
  overflow-x: auto;
  border: 1px solid var(--color-divider);
  border-radius: var(--radius-lg);
  margin-bottom: var(--space-4);
}
table { font-size: var(--text-sm); min-width: 720px; }
thead th {
  text-align: left;
  padding: var(--space-3) var(--space-4);
  background: var(--color-surface-offset);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--color-text-muted);
  white-space: nowrap;
}
tbody td {
  padding: var(--space-3) var(--space-4);
  border-bottom: 1px solid var(--color-divider);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}
tbody tr:last-child td { border-bottom: none; }
tbody tr:hover { background: var(--color-surface-offset); }
td.name-cell { font-weight: 600; white-space: normal; }
td.err-good { color: var(--color-primary); font-weight: 600; }
td.err-bad { color: var(--color-flaw); font-weight: 600; }

.source-note {
  font-size: var(--text-xs);
  color: var(--color-text-faint);
  max-width: none;
}

/* ============================================================
   CLOSING
   ============================================================ */
.closing-section {
  max-width: var(--content-wide);
  margin-inline: auto;
  padding: clamp(var(--space-16), 8vw, var(--space-24)) var(--space-6);
  text-align: center;
}
.closing-inner { max-width: 68ch; margin-inline: auto; }
.closing-inner h2 { font-size: var(--text-xl); margin-bottom: var(--space-4); }
.closing-inner p { color: var(--color-text-muted); margin-inline: auto; font-size: var(--text-lg); }

/* ============================================================
   FOOTER
   ============================================================ */
.site-footer {
  border-top: 1px solid var(--color-divider);
  padding: var(--space-8) var(--space-6);
}
.footer-inner {
  max-width: var(--content-wide);
  margin-inline: auto;
  font-size: var(--text-xs);
  color: var(--color-text-faint);
}

@media (prefers-reduced-motion: reduce) {
  * { transition-duration: 0.01ms !important; }
}