:root {
  color-scheme: light dark;
  /* Neutral greys — kept off the blue spectrum so the controls
     don't compete with the colourful fractal canvas. */
  --accent: #d1d5db;
  --accent-dim: #6b7280;
  --surface: #181c22;
  --surface-raised: #1f242d;
  --border: #2e3340;
  --text: #e2e8f0;
  --text-muted: #8a93a8;
  --bg: #0e1117;
  --btn-hover-bg: #262d3a;
  --panel-bg: #252b38;
  --option-hover: #2e3748;
  --option-selected-bg: rgba(209,213,219,0.10);
  --radius: 0.45rem;
  --transition: 140ms ease;
}
@media (prefers-color-scheme: light) {
  :root {
    --accent: #1a202c;
    --accent-dim: #4a5568;
    --surface: #f0f4f8;
    --surface-raised: #ffffff;
    --border: #c8d0dc;
    --text: #1a202c;
    --text-muted: #5a6478;
    --bg: #e2e8f0;
    --btn-hover-bg: #dde3ec;
    --panel-bg: #ffffff;
    --option-hover: #e8edf4;
    --option-selected-bg: rgba(26,32,44,0.08);
  }
}
*, *::before, *::after { -webkit-tap-highlight-color: transparent; }
html, body { margin: 0; height: 100%; background: var(--bg); color: var(--text);
  font-family: system-ui, -apple-system, sans-serif; overflow: hidden;
  touch-action: none;
  -webkit-text-size-adjust: 100%; -webkit-tap-highlight-color: transparent; }
body { display: flex; flex-direction: column; height: 100vh;
  height: 100dvh; padding-top: env(safe-area-inset-top);
  padding-left: env(safe-area-inset-left);
  padding-right: env(safe-area-inset-right);
  padding-bottom: env(safe-area-inset-bottom);
  box-sizing: border-box; }

/* ── Header ───────────────────────────────────────────────────── */
header {
  padding: 0.55rem 1rem;
  display: flex; gap: 0.6rem 0.9rem; align-items: center; flex-wrap: wrap;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  flex: 0 0 auto;
  touch-action: manipulation;
}
header h1 { font-size: 1rem; margin: 0; font-weight: 700;
  letter-spacing: 0.01em; color: var(--text); }
header h1 .short { display: none; }

/* ── Labels ───────────────────────────────────────────────────── */
header label {
  font-size: 0.78rem; font-weight: 500; color: var(--text-muted);
  display: inline-flex; align-items: center; gap: 0.4rem;
  letter-spacing: 0.03em; text-transform: uppercase;
}

/* ── Hide native selects; they live in DOM only for JS ───────────── */
header select { display: none !important; }

/* ── Custom dropdown ───────────────────────────────────────── */
.csel { position: relative; display: inline-block; font-size: 0.85rem; }
.csel__trigger {
  display: inline-flex; align-items: center; gap: 0.45rem;
  font: inherit; font-size: 0.85rem; font-weight: 500;
  color: var(--text); background: var(--surface-raised);
  border: 1px solid var(--border); border-radius: var(--radius);
  padding: 0.3rem 0.6rem 0.3rem 0.7rem; min-height: 2rem;
  cursor: pointer; white-space: nowrap; user-select: none;
  -webkit-tap-highlight-color: transparent;
  transition: border-color var(--transition), box-shadow var(--transition);
}
.csel__trigger:hover { border-color: #4a5568; }
.csel__trigger:focus-visible {
  outline: none; border-color: var(--text-muted);
}
.csel[data-open] .csel__trigger {
  border-color: var(--text-muted);
}
.csel__chevron { flex-shrink: 0; opacity: 0.5;
  transition: transform var(--transition); }
.csel[data-open] .csel__chevron { transform: rotate(180deg); }
.csel__panel {
  display: none; position: absolute;
  top: calc(100% + 0.3rem); left: 0; min-width: 100%;
  background: var(--panel-bg); border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: 0 8px 24px rgba(0,0,0,0.2);
  z-index: 100; padding: 0.25rem 0;
}
.csel[data-open] .csel__panel { display: block; }
.csel__option {
  display: block; width: 100%;
  font: inherit; font-size: 0.85rem;
  color: var(--text); background: none; border: none;
  padding: 0.45rem 0.85rem; text-align: left;
  cursor: pointer; white-space: nowrap;
  transition: background var(--transition);
}
.csel__option:hover { background: var(--option-hover); }
.csel__option[aria-selected="true"] {
  color: var(--text); font-weight: 700; background: none;
}

/* ── Number input ─────────────────────────────────────────────── */
header input[type="number"] {
  font: inherit; font-size: 0.85rem; font-weight: 500;
  color: var(--text); background: var(--surface-raised);
  border: 1px solid var(--border); border-radius: var(--radius);
  padding: 0.3rem 0.55rem; min-height: 2rem;
  box-sizing: border-box;
  outline: none;
  transition: border-color var(--transition), box-shadow var(--transition);
}
header input[type="number"]:hover { border-color: #4a5568; }
header input[type="number"]:focus {
  border-color: var(--text-muted);
}
header input[type="number"] { width: 6rem; }
#juliaControls input[type="number"] { width: 5.2rem; }
/* hide browser spin arrows */
header input[type="number"]::-webkit-inner-spin-button,
header input[type="number"]::-webkit-outer-spin-button { -webkit-appearance: none; margin: 0; }
header input[type="number"] { -moz-appearance: textfield; appearance: textfield; }

/* ── Controls wrapper — transparent on desktop ───────────────────── */
#controls { display: contents; }

/* ── Controls toggle button (mobile-only) ───────────────────────── */
#controlsToggle {
  display: none;
  margin-left: auto;
  align-items: center;
  justify-content: center;
  padding: 0.3rem 0.55rem; min-height: 2rem;
  background: var(--surface-raised);
  border: 1px solid var(--border); border-radius: var(--radius);
  color: var(--text); cursor: pointer;
  transition: background var(--transition), border-color var(--transition), color var(--transition);
}
#controlsToggle:hover { background: var(--btn-hover-bg); border-color: var(--text-muted); }
#controlsToggle[aria-expanded="true"] {
  border-color: var(--text); background: var(--btn-hover-bg);
  font-weight: 700;
}

/* ── Reset button ─────────────────────────────────────────────────── */
header > button, #reset {
  font: inherit; font-size: 0.82rem; font-weight: 600;
  padding: 0.3rem 0.85rem; min-height: 2rem;
  background: var(--surface-raised);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  cursor: pointer;
  letter-spacing: 0.02em;
  -webkit-tap-highlight-color: transparent;
  transition: background var(--transition), border-color var(--transition), box-shadow var(--transition);
}
header > button:hover, #reset:hover {
  background: var(--btn-hover-bg);
  border-color: var(--text-muted);
}
header > button:active, #reset:active {
  background: var(--btn-hover-bg);
  border-color: var(--text-muted);
}
header > button:focus-visible, #reset:focus-visible {
  outline: none;
}

/* ── Toggle checkbox ─────────────────────────────────────────── */
/* Hide the native checkbox; replace with a CSS pill toggle */
header input[type="checkbox"] { display: none; }
header label:has(input[type="checkbox"]) {
  cursor: pointer; user-select: none; gap: 0.5rem;
}
header label:has(input[type="checkbox"])::after {
  content: '';
  display: inline-block;
  width: 2.2rem; height: 1.15rem;
  background: var(--surface-raised);
  border: 1px solid var(--border);
  border-radius: 999px;
  position: relative;
  transition: background var(--transition), border-color var(--transition);
  box-shadow: inset 0 1px 3px rgba(0,0,0,0.4);
  vertical-align: middle;
}
header label:has(input[type="checkbox"])::before {
  content: '';
  display: inline-block;
  width: 0.7rem; height: 0.7rem;
  background: var(--text-muted);
  border-radius: 50%;
  position: relative;
  transition: transform var(--transition), background var(--transition);
  /* stacked after the pill — controlled via JS-free CSS trick below */
}
/* Use a wrapping span trick instead — simpler: style the label after-pseudo for the track and rely on :checked for the thumb by keeping checkbox visible but styled */
/* Actually, let's do a cleaner implementation with visible checkbox styled via accent-color and a custom look */
header input[type="checkbox"] {
  display: inline-block;
  appearance: none; -webkit-appearance: none;
  width: 2.2rem; height: 1.15rem;
  background: var(--surface-raised);
  border: 1px solid var(--border);
  border-radius: 999px;
  position: relative;
  cursor: pointer;
  transition: background var(--transition), border-color var(--transition);
  vertical-align: middle;
  flex-shrink: 0;
}
header input[type="checkbox"]::before {
  content: '';
  position: absolute;
  top: 50%; left: 0.17rem;
  transform: translateY(-50%);
  width: 0.72rem; height: 0.72rem;
  background: var(--text-muted);
  border-radius: 50%;
  transition: transform var(--transition), background var(--transition);
}
header input[type="checkbox"]:checked {
  background: var(--accent-dim);
  border-color: var(--accent);
}
header input[type="checkbox"]:checked::before {
  transform: translateY(-50%) translateX(1.05rem);
  background: #fff;
}
header input[type="checkbox"]:focus-visible {
  outline: none;
}
/* Undo the bad ::after trick above */
header label:has(input[type="checkbox"])::after,
header label:has(input[type="checkbox"])::before { display: none; }

/* ── Range slider ─────────────────────────────────────────────── */
/* Visible on desktop alongside the number input — drag for casual
   changes, type for an exact value. Mobile (below) hides the input
   and widens the slider, since touch can't comfortably drive a
   number field. */
#iterRange { accent-color: var(--accent); display: inline-block;
  width: 8rem; vertical-align: middle; }
.iter-label-short { display: none; }
.iter-label-long { display: inline; }

/* ── Julia controls ──────────────────────────────────────────── */
#iterValue { display: none; }
#juliaControls { display: none; gap: 0.4rem; align-items: center; }
#juliaControls.show { display: inline-flex; }

/* ── Status ───────────────────────────────────────────────────── */
#status { font-size: 0.78rem; color: var(--text-muted); margin-left: auto;
  font-variant-numeric: tabular-nums; }

/* ── Canvas area ─────────────────────────────────────────────── */
main { flex: 1 1 auto; position: relative; overflow: hidden;
  touch-action: none; }
canvas { position: absolute; inset: 0; width: 100%; height: 100%;
  display: block; cursor: crosshair; }
#canvas { background: #000; image-rendering: pixelated;
  image-rendering: crisp-edges; }
#gpu, #webgpu { background: #000; }
#axes { pointer-events: none; background: transparent; }
.hint { position: absolute; left: 0.75rem; bottom: 0.5rem;
  font-size: 0.75rem; color: var(--text-muted); pointer-events: none;
  margin: 0; }

/* ── Mobile / narrow viewports ──────────────────────────────── */
@media (max-width: 720px), (pointer: coarse) {
  header { padding: 0.45rem 0.65rem; gap: 0.45rem 0.7rem; position: relative; }
  #controlsToggle { display: inline-flex; }
  #controls {
    display: flex; flex-wrap: wrap; gap: 0.5rem 0.75rem; align-items: center;
    position: absolute; top: 100%; left: 0; right: 0;
    background: var(--surface); border-bottom: 1px solid var(--border);
    padding: 0.6rem 0.65rem;
    z-index: 50;
    /* hidden state */
    visibility: hidden; opacity: 0; transform: translateY(-0.4rem);
    transition: opacity 180ms ease, transform 180ms ease, visibility 0s 180ms;
  }
  #controls.open {
    visibility: visible; opacity: 1; transform: translateY(0);
    transition: opacity 180ms ease, transform 180ms ease;
  }
  header h1 .long { display: none; }
  header h1 .short { display: inline; }
  header label { font-size: 0.9rem; }
  .csel__trigger,
  header input[type="number"],
  header > button, #reset {
    font-size: 1rem; min-height: 2.4rem;
    padding: 0.4rem 0.65rem;
  }
  .csel__option { font-size: 1rem; padding: 0.55rem 1rem; }
  #iter { display: none; }
  #iterRange { display: inline-block; width: 9rem; }
  .iter-label-long { display: none; }
  .iter-label-short { display: inline; }
  #iterValue { display: inline; font-variant-numeric: tabular-nums; min-width: 2.5rem;
    text-align: right; color: var(--text); }
  #status { display: none; }
  .hint { font-size: 0.7rem; left: 0.5rem; bottom: 0.3rem; }
}