/* ---------------- themes ---------------- */
:root,
[data-theme="dark"] {
  --page-grad-1: #667eea;
  --page-grad-2: #764ba2;
  --card: #1e1e2e;
  --display-bg: #16161f;
  --text: #ffffff;
  --muted: #8888a0;
  --key: #2d2d44;
  --key-text: #ffffff;
  --fn: #26263a;
  --fn-text: #c4b5fd;
  --op: #3d3d5c;
  --op-text: #a5b4fc;
  --accent: #667eea;
  --accent-text: #ffffff;
  --danger: #ef4444;
  --panel: #232336;
  --hover: #34344f;
  --focus: #a5b4fc;
  --shadow: rgba(0, 0, 0, 0.4);
  --border: rgba(255, 255, 255, 0.08);
}

[data-theme="light"] {
  --page-grad-1: #a5b4fc;
  --page-grad-2: #c4b5fd;
  --card: #ffffff;
  --display-bg: #f1f2f8;
  --text: #1e1e2e;
  --muted: #6b7280;
  --key: #eceef6;
  --key-text: #1e1e2e;
  --fn: #ede9fe;
  --fn-text: #6d28d9;
  --op: #dfe1f0;
  --op-text: #4f46e5;
  --accent: #667eea;
  --accent-text: #ffffff;
  --danger: #dc2626;
  --panel: #f8f8fc;
  --hover: #e2e4f0;
  --focus: #4f46e5;
  --shadow: rgba(80, 70, 140, 0.35);
  --border: rgba(0, 0, 0, 0.08);
}

[data-theme="oled"] {
  --page-grad-1: #000000;
  --page-grad-2: #0a0a0a;
  --card: #000000;
  --display-bg: #0a0a0a;
  --text: #f3f4f6;
  --muted: #6b7280;
  --key: #17171f;
  --key-text: #f3f4f6;
  --fn: #14141c;
  --fn-text: #c4b5fd;
  --op: #1a1a26;
  --op-text: #a5b4fc;
  --accent: #667eea;
  --accent-text: #ffffff;
  --danger: #ef4444;
  --panel: #0d0d14;
  --hover: #1f1f2e;
  --focus: #a5b4fc;
  --shadow: rgba(0, 0, 0, 0.8);
  --border: rgba(255, 255, 255, 0.08);
}

/* Robotic / futuristic. Placed before the [data-hc="on"] block on purpose:
   that block shares the same specificity, so being later lets high contrast
   override these colours for any theme. */
[data-theme="robot"] {
  --page-grad-1: #04121a;
  --page-grad-2: #0a0618;
  --card: #0a141b;
  --display-bg: #050d13;
  --text: #d6f6ff;
  --muted: #5f93a6;
  --key: #101f28;
  --key-text: #cbeeff;
  --fn: #0d2b2c;
  --fn-text: #46e0c8;
  --op: #0f3242;
  --op-text: #35e6ff;
  --accent: #00d9ff;
  --accent-text: #001318;
  /* #e11d48 rather than a lighter red: white on it is 4.70:1, which clears
     WCAG AA. The brighter reds used elsewhere measure 3.2-3.8:1. */
  --danger: #e11d48;
  --panel: #0b1820;
  --hover: #16303d;
  --focus: #7ff4ff;
  --shadow: rgba(0, 0, 0, 0.75);
  --border: rgba(0, 217, 255, 0.22);

  /* robot-only accents */
  --r-cyan: #00d9ff;
  --r-amber: #ffb020;
  --r-font: 'Consolas', 'SF Mono', 'Roboto Mono', 'Menlo', 'DejaVu Sans Mono', monospace;
  /* Chamfered corners. clip-path and box-shadow cannot be combined, so glowing
     elements use filter: drop-shadow() instead, which follows the clip. */
  --r-chamfer: polygon(9px 0, 100% 0, 100% calc(100% - 9px), calc(100% - 9px) 100%, 0 100%, 0 9px);
  --r-chamfer-sm: polygon(5px 0, 100% 0, 100% calc(100% - 5px), calc(100% - 5px) 100%, 0 100%, 0 5px);
}

/* High contrast overrides — applied for any theme when data-hc="on" */
[data-hc="on"] {
  --card: #000000;
  --display-bg: #000000;
  --text: #ffff00;
  --muted: #ffffff;
  --key: #1a1a1a;
  --key-text: #ffffff;
  --fn: #1a1a1a;
  --fn-text: #00ffff;
  --op: #262626;
  --op-text: #00ffff;
  --accent: #ffff00;
  --accent-text: #000000;
  /* #e11d48 rather than a light red: the danger key paints white text on this,
     and white on a light red measures only ~2.9:1 — the least legible control in
     the mode whose whole purpose is legibility. */
  --danger: #e11d48;
  --panel: #000000;
  --hover: #333333;
  --focus: #ffff00;
  --border: #ffffff;
}

/* ---------------- base ---------------- */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  -webkit-tap-highlight-color: transparent;
}

html, body {
  touch-action: manipulation; /* prevent double-tap zoom */
  -webkit-text-size-adjust: 100%;
}

/* Author display rules (flex/grid) would otherwise beat the UA's
   `[hidden] { display: none }`, so enforce it globally. */
[hidden] {
  display: none !important;
}

/* Prevent text selection on buttons */
button {
  -webkit-user-select: none;
  user-select: none;
}

body {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
  background: linear-gradient(135deg, var(--page-grad-1) 0%, var(--page-grad-2) 100%);
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
}

.calculator {
  position: relative;
  background: var(--card);
  border-radius: 20px;
  padding: 20px;
  padding-top: calc(20px + env(safe-area-inset-top));
  padding-bottom: calc(20px + env(safe-area-inset-bottom));
  padding-left: calc(20px + env(safe-area-inset-left));
  padding-right: calc(20px + env(safe-area-inset-right));
  box-shadow: 0 20px 60px var(--shadow);
  width: 100%;
  max-width: 420px;
  transition: background 0.25s, max-width 0.25s ease;
}

/* ---------------- toolbar ----------------
   Ten buttons in a 380px card, so the row must wrap rather than overflow.
   `justify-content: flex-end` with overflowing flex items pushes them out
   of the left edge (they escaped the card entirely), hence flex-wrap.
   Buttons are uniform-width so the row reads as one control strip. */
.toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: flex-end;
  gap: 6px;
  margin-bottom: 12px;
}

.tool-group {
  display: flex;
  align-items: center;
  gap: 6px;
}

/* hairline divider between functional groups */
.tool-group + .tool-group {
  margin-left: 2px;
  padding-left: 8px;
  border-left: 1px solid var(--border);
}

.tool {
  border: none;
  border-radius: 9px;
  background: var(--key);
  color: var(--muted);
  font-family: inherit;
  font-size: 14px;
  line-height: 1;
  min-width: 30px;
  height: 32px;
  padding: 0 6px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: filter 0.15s, color 0.15s, background 0.15s, box-shadow 0.15s;
}

.tool:hover { filter: brightness(1.2); color: var(--text); }

.tool:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
}

/* Active toggle: tinted plate + accent ring, not just a brightness shift. */
.tool[aria-pressed="true"] {
  background: var(--op);
  color: var(--op-text);
  box-shadow: inset 0 0 0 1.5px var(--accent);
}

.tool[aria-pressed="true"]:hover { filter: brightness(1.1); color: var(--op-text); }

.tool:disabled { opacity: 0.4; cursor: not-allowed; }

/* ---------------- display ---------------- */
.display {
  background: var(--display-bg);
  border-radius: 12px;
  padding: 14px 18px;
  margin-bottom: 16px;
  text-align: right;
  overflow: hidden;
}

.display-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  min-height: 22px;
}

.mem-badge {
  background: var(--accent);
  color: var(--accent-text);
  font-size: 11px;
  font-weight: 700;
  border-radius: 5px;
  padding: 1px 6px;
  flex: none;
}

.history-line {
  color: var(--muted);
  font-size: 15px;
  min-height: 20px;
  word-break: break-all;
  flex: 1;
  text-align: right;
}

.current {
  display: block;
  color: var(--text);
  font-size: 40px;
  font-weight: 300;
  line-height: 1.3;
  min-height: 52px;
  word-break: break-all;
}

.current.len-md { font-size: 30px; }
.current.len-lg { font-size: 22px; }

/* ---------------- button pads ---------------- */
.pad {
  display: grid;
  gap: 10px;
}

.pad.main   { grid-template-columns: repeat(4, 1fr); }
.pad.memory { grid-template-columns: repeat(4, 1fr); margin-bottom: 10px; }
.pad.sci    { grid-template-columns: repeat(5, 1fr); margin-bottom: 10px; }

.pad button {
  border: none;
  border-radius: 12px;
  padding: 16px 0;
  font-size: 20px;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
  background: var(--key);
  color: var(--key-text);
  transition: filter 0.15s, transform 0.05s;
  -webkit-tap-highlight-color: transparent;
}

.pad button:hover { filter: brightness(1.2); }
.pad button:active { transform: scale(0.96); }

.pad button.op      { background: var(--op); color: var(--op-text); }
.pad button.equals  { background: var(--accent); color: var(--accent-text); }
.pad button.danger  { background: var(--danger); color: #ffffff; }

.pad.memory button.mem {
  padding: 9px 0;
  font-size: 13px;
  font-weight: 600;
  background: transparent;
  color: var(--muted);
}
.pad.memory button.mem:hover { color: var(--op-text); background: var(--key); }

.pad.sci button.fn {
  padding: 11px 0;
  font-size: 15px;
  background: var(--fn);
  color: var(--fn-text);
}

/* ---------------- horizontal scientific mode ---------------- */
.calculator.sci-on {
  max-width: 780px;
}

.calculator.sci-on #calculator-view {
  display: grid;
  grid-template-columns: minmax(210px, 250px) minmax(0, 1fr);
  grid-template-areas:
    "toolbar toolbar"
    "sci     display"
    "sci     memory"
    "sci     main";
  column-gap: 16px;
}

.calculator.sci-on #calculator-view > .toolbar { grid-area: toolbar; }
.calculator.sci-on #calculator-view > .display { grid-area: display; }
.calculator.sci-on #calculator-view > .pad.memory { grid-area: memory; }
.calculator.sci-on #calculator-view > .pad.main { grid-area: main; }

.calculator.sci-on #sci-pad {
  grid-area: sci;
  grid-template-columns: repeat(3, 1fr);
  align-content: start;
  margin-bottom: 0;
}

.calculator.sci-on #sci-pad button.fn {
  padding: 13px 0;
  font-size: 14px;
}

/* keyboard press feedback */
.pad button.flash {
  animation: flash 0.15s ease;
}
@keyframes flash {
  0% { filter: brightness(1.5); transform: scale(0.96); }
  100% { filter: brightness(1); transform: scale(1); }
}

/* density variants */
.calculator.density-small .pad button { padding: 11px 0; font-size: 17px; }
.calculator.density-small .current { font-size: 32px; }
.calculator.density-small .pad.sci button.fn { padding: 8px 0; font-size: 13px; }
.calculator.density-large .pad button { padding: 20px 0; font-size: 23px; }
.calculator.density-large .current { font-size: 46px; }
.calculator.density-large .pad.sci button.fn { padding: 14px 0; font-size: 16px; }

/* mode select + small numeric inputs inside function rows */
.fn-mode {
  background: var(--card);
  border: 1.5px solid var(--key);
  border-radius: 8px;
  padding: 9px 8px;
  color: var(--text);
  font-family: inherit;
  font-size: 13px;
  outline: none;
  cursor: pointer;
  min-height: 44px;
}
.fn-mode:focus { border-color: var(--accent); }

.fn-t {
  background: var(--card);
  border: 1.5px solid var(--key);
  border-radius: 8px;
  padding: 8px 6px;
  color: var(--text);
  font-family: inherit;
  font-size: 14px;
  width: 56px;
  outline: none;
}
.fn-t:focus { border-color: var(--accent); }

/* ---------------- history panel ---------------- */
.history-panel {
  position: absolute;
  inset: 16px;
  z-index: 10;
  background: var(--panel);
  border-radius: 16px;
  padding: 16px;
  display: flex;
  flex-direction: column;
  box-shadow: 0 10px 40px var(--shadow);
}

.history-head {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text);
  font-weight: 600;
  margin-bottom: 10px;
}

.history-title { flex: 1; }

.history-head button {
  border: none;
  background: var(--key);
  color: var(--muted);
  border-radius: 8px;
  padding: 6px 12px;
  font-size: 13px;
  font-family: inherit;
  cursor: pointer;
  transition: filter 0.15s, color 0.15s;
}

.history-head .back {
  background: var(--accent);
  color: var(--accent-text);
  font-weight: 600;
}
.history-head .back:hover { filter: brightness(1.15); }
.history-head .clear:hover { color: var(--danger); filter: brightness(1.15); }

.history-list {
  list-style: none;
  overflow-y: auto;
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.history-item {
  width: 100%;
  border: none;
  background: transparent;
  border-radius: 10px;
  padding: 8px 12px;
  cursor: pointer;
  text-align: right;
  font-family: inherit;
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.history-item:hover { background: var(--hover); }

.history-item .expr { color: var(--muted); font-size: 13px; word-break: break-all; }
.history-item .res  { color: var(--text); font-size: 19px; word-break: break-all; }

.history-empty {
  color: var(--muted);
  font-size: 14px;
  text-align: center;
  margin: auto;
  line-height: 1.6;
}

/* ---------------- values table ---------------- */
.table-panel {
  background: var(--panel);
  border-radius: 16px;
  padding: 16px;
  box-shadow: 0 10px 40px var(--shadow);
  max-height: 40vh;
  overflow: auto;
}

.table-step-label {
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--muted);
  font-size: 13px;
}

.table-step-label input {
  width: 70px;
  background: var(--display-bg);
  border: 1.5px solid var(--key);
  border-radius: 8px;
  padding: 4px 8px;
  color: var(--text);
  font-family: inherit;
  font-size: 13px;
}

.table-scroll { overflow-x: auto; }

#values-table {
  border-collapse: collapse;
  width: 100%;
  font-family: 'Consolas', 'Monaco', monospace;
  font-size: 12px;
  color: var(--text);
}

#values-table th,
#values-table td {
  border: 1px solid var(--border);
  padding: 4px 10px;
  text-align: right;
  white-space: nowrap;
}

#values-table th {
  background: var(--key);
  color: var(--op-text);
  font-weight: 600;
}

#values-table tr:nth-child(even) td { background: var(--display-bg); }

/* ---------------- converter ---------------- */
.convert-body {
  display: flex;
  flex-direction: column;
  gap: 12px;
  color: var(--text);
  /* Keep fields readable when the card is widened (scientific mode). */
  width: 100%;
  max-width: 420px;
  margin: 0 auto;
}

.convert-label {
  display: flex;
  flex-direction: column;
  gap: 6px;
  color: var(--muted);
  font-size: 13px;
}

.convert-row {
  display: flex;
  gap: 10px;
  align-items: center;
}

.convert-row .fn-text { flex: 1; }

.convert-arrow {
  text-align: center;
  color: var(--muted);
  font-size: 18px;
}

.convert-result {
  flex: 1;
  background: var(--display-bg);
  border: 1.5px solid var(--key);
  border-radius: 8px;
  padding: 10px 12px;
  font-family: 'Consolas', 'Monaco', monospace;
  font-size: 18px;
  color: var(--accent-text);
  background: var(--accent);
  min-height: 44px;
  display: flex;
  align-items: center;
}

.convert-note {
  color: var(--muted);
  font-size: 12px;
  line-height: 1.5;
}

/* per-category caveat (ISO rounding, decimal vs binary prefixes, ...) */
.convert-hint {
  color: var(--op-text);
  background: var(--display-bg);
  border-left: 3px solid var(--accent);
  border-radius: 6px;
  padding: 8px 10px;
  font-size: 12px;
  line-height: 1.5;
}

.convert-hint[hidden] { display: none; }

/* swap button */
.convert-swap-row { justify-content: center; }

.convert-swap {
  background: var(--card);
  color: var(--op-text);
  border: 1.5px solid var(--key);
  border-radius: 999px;
  width: 40px;
  height: 40px;
  font-size: 18px;
  line-height: 1;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: transform 0.15s ease, background 0.15s ease, border-color 0.15s ease;
}

.convert-swap:hover { background: var(--hover); border-color: var(--accent); }
.convert-swap:active { transform: rotate(180deg) scale(0.94); }
.convert-swap:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }

/* live rate status line */
.fx-status {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
  font-size: 12px;
  line-height: 1.5;
  color: var(--muted);
  background: var(--display-bg);
  border: 1px solid var(--border);
  border-left: 3px solid var(--muted);
  border-radius: 8px;
  padding: 8px 10px;
}

.fx-status[data-state="live"] { border-left-color: #22c55e; }
.fx-status[data-state="stale"] { border-left-color: #f59e0b; }
.fx-status[data-state="offline"] { border-left-color: #ef4444; }

.fx-status span { flex: 1 1 140px; min-width: 0; }

.fx-refresh {
  flex: 0 0 auto;
  background: transparent;
  color: var(--accent);
  border: 1.5px solid var(--accent);
  border-radius: 999px;
  padding: 4px 10px;
  font-size: 12px;
  font-family: inherit;
  cursor: pointer;
  white-space: nowrap;
}

.fx-refresh:hover { background: var(--accent); color: var(--accent-text); }
.fx-refresh:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }
.fx-refresh:disabled { opacity: 0.5; cursor: progress; }

/* currency dropdowns can be long — keep them readable */
#convert-from,
#convert-to { max-width: 58%; text-overflow: ellipsis; }

/* optgroup headings in the category dropdown */
#convert-category option:disabled { color: var(--muted); }

/* ---------------- symbolic solver ---------------- */
.cas-body {
  display: flex;
  flex-direction: column;
  gap: 12px;
  color: var(--text);
  width: 100%;
  max-width: 460px;
  margin: 0 auto;
}

#cas-input {
  width: 100%;
  font-size: 17px;
  padding: 12px;
}

.cas-row { gap: 10px; }

.cas-var {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--muted);
  font-size: 13px;
  flex: 0 0 auto;
}

.cas-var input { width: 52px; text-align: center; }

.cas-go {
  flex: 1 1 auto;
  background: var(--accent);
  color: var(--accent-text);
  border: none;
  border-radius: 10px;
  padding: 12px 18px;
  font-family: inherit;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  min-height: 44px;
}

.cas-go:hover { filter: brightness(1.1); }
.cas-go:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }
.cas-go:disabled { opacity: 0.6; cursor: progress; }

.cas-help { margin: 0; }

.cas-examples {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.cas-example {
  background: var(--key);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 6px 12px;
  font-family: inherit;
  font-size: 12px;
  color: var(--muted);
  cursor: pointer;
  min-height: 32px;
}

.cas-example:hover { background: var(--hover); color: var(--text); }
.cas-example:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }

.cas-result {
  border-radius: 12px;
  padding: 12px 14px;
  background: var(--display-bg);
  border: 1px solid var(--border);
  min-height: 24px;
  display: none;
}

.cas-result.ok, .cas-result.error { display: block; }

.cas-result.error {
  color: var(--danger);
  border-color: var(--danger);
}

.cas-label {
  display: block;
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
  margin-bottom: 4px;
}

.cas-value {
  font-family: 'Cambria Math', 'Latin Modern Math', Georgia, serif;
  font-size: 19px;
  line-height: 1.45;
  color: var(--text);
  word-break: break-word;
}

.cas-notes:empty { display: none; }

.cas-note {
  margin: 0;
  font-size: 12px;
  line-height: 1.5;
  color: var(--muted);
  padding-left: 14px;
  position: relative;
}

.cas-note::before {
  content: '\2022';
  position: absolute;
  left: 2px;
  color: var(--accent);
}

/* ---------------- accessibility ---------------- */
button:focus-visible,
.history-item:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
}

/* ---------------- graph view ---------------- */
.calculator.graph-on {
  max-width: 1060px;
}

#graph-view {
  display: grid;
  grid-template-columns: minmax(0, 1.55fr) minmax(280px, 1fr);
  grid-template-areas:
    "toolbar toolbar"
    "canvas  controls";
  gap: 16px;
  align-items: start;
}

#graph-view > .toolbar { grid-area: toolbar; }
#graph-view > .graph-canvas-wrap { grid-area: canvas; }

#graph-view > .graph-controls {
  grid-area: controls;
  grid-template-columns: 1fr;
  max-height: 72vh;
  overflow-y: auto;
  padding-right: 4px;
  scrollbar-width: thin;
}

#graph-view .toolbar {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 0;
}

#graph-view .toolbar button {
  border: none;
  border-radius: 10px;
  background: var(--key);
  color: var(--muted);
  font-size: 15px;
  line-height: 1;
  padding: 8px 12px;
  cursor: pointer;
  transition: filter 0.15s, color 0.15s;
}

#graph-view .toolbar button:hover { filter: brightness(1.2); color: var(--text); }

#graph-view .toolbar .back {
  background: var(--accent);
  color: var(--accent-text);
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 6px;
}

#graph-view .toolbar .back:hover { filter: brightness(1.15); }

.graph-title {
  color: var(--text);
  font-weight: 600;
  font-size: 18px;
  /* min-width:0 lets the title collapse on very narrow screens; without it the
     default min-width:auto holds the row at its min-content width and pushes
     the last toolbar buttons outside the card. */
  flex: 1 1 auto;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.graph-canvas-wrap {
  background: var(--display-bg);
  border-radius: 12px;
  padding: 12px;
  overflow: hidden;
  width: 100%;
  box-shadow: inset 0 2px 8px rgba(0, 0, 0, 0.08);
  position: relative;
}

.graph-canvas-wrap::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: 
    radial-gradient(circle at 20% 20%, rgba(99, 102, 241, 0.03) 0%, transparent 50%),
    radial-gradient(circle at 80% 80%, rgba(236, 72, 153, 0.03) 0%, transparent 50%);
  pointer-events: none;
  border-radius: 12px;
}

#graph-canvas {
  display: block;
  width: 100%;
  height: auto;
  max-height: 60vh;
  /* Press-and-drag moves the plot, so advertise that with a grab hand.
     Inspect mode keeps the crosshair, which signals "read a value here".
     grapher.js keeps data-mode in step with interactionMode. */
  cursor: grab;
  border-radius: 8px;
  touch-action: none; /* prevent browser handling of touch events */
  position: relative;
  z-index: 1;
}

#graph-canvas[data-mode="inspect"] { cursor: crosshair; }

/* While a drag is in flight the hand is closed, which is the standard
   "you are moving this" signal. */
#graph-canvas.is-panning { cursor: grabbing; }

/* Suppress the text caret that a stray drag would otherwise leave behind. */
#graph-canvas:active { user-select: none; }

/* Keyboard hint under the plot, and a visible focus ring now that the canvas
   is reachable by Tab. */
.graph-key-hint {
  margin-top: 8px;
  color: var(--muted);
  font-size: 12px;
  line-height: 1.9;
  text-align: center;
}

.graph-key-hint kbd {
  font-family: inherit;
  font-size: 11px;
  border: 1px solid var(--border);
  border-bottom-width: 2px;
  border-radius: 4px;
  padding: 0 5px;
  margin: 0 1px;
  background: var(--key);
  color: var(--text);
}

#graph-canvas:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
}

.graph-controls {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 16px;
}

.graph-section {
  background: var(--card);
  border-radius: 12px;
  padding: 16px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
  border: 1px solid var(--border);
}

.graph-section h3 {
  color: var(--text);
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 12px;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.graph-section h3::before {
  content: '';
  display: inline-block;
  width: 3px;
  height: 14px;
  background: var(--accent);
  border-radius: 2px;
}

.fn-input-row {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 8px;
  flex-wrap: wrap;
  padding: 6px 8px;
  border-radius: 10px;
  transition: opacity 0.2s, background 0.2s;
  background: var(--display-bg);
}

.fn-input-row:hover {
  background: var(--hover);
}

.fn-input-row.fn-hidden {
  opacity: 0.5;
}

.fn-input-row.fn-invalid .fn-text {
  border-color: #ef4444;
  box-shadow: 0 0 0 2px rgba(239, 68, 68, 0.15);
}

.fn-swatch {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  border: 2px solid var(--border);
  cursor: pointer;
  flex-shrink: 0;
  padding: 0;
  transition: transform 0.15s, box-shadow 0.15s;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.15);
}

.fn-swatch:hover {
  transform: scale(1.15);
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.2);
}

.fn-label {
  color: var(--muted);
  font-size: 13px;
  min-width: 50px;
  flex-shrink: 0;
  font-weight: 500;
}

.fn-text {
  flex: 1;
  min-width: 120px;
  background: var(--card);
  border: 1.5px solid var(--key);
  border-radius: 8px;
  padding: 10px 12px;
  color: var(--text);
  font-family: 'Consolas', 'Monaco', monospace;
  font-size: 16px; /* prevent iOS zoom on focus */
  outline: none;
  transition: border-color 0.15s, box-shadow 0.15s;
}

.fn-text:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

.fn-toggle {
  background: var(--key);
  border: none;
  border-radius: 8px;
  padding: 10px 14px;
  cursor: pointer;
  font-size: 14px;
  color: var(--text);
  transition: filter 0.15s, transform 0.1s;
  min-width: 44px;
  min-height: 44px;
}

.fn-toggle:hover {
  filter: brightness(1.2);
}

.fn-toggle:active {
  transform: scale(0.95);
}

.fn-delete {
  background: transparent;
  border: 1px solid var(--danger);
  border-radius: 8px;
  padding: 10px 14px;
  cursor: pointer;
  font-size: 14px;
  color: var(--danger);
  transition: background 0.15s, color 0.15s, transform 0.1s;
  min-width: 44px;
  min-height: 44px;
}

.fn-delete:hover {
  background: var(--danger);
  color: #fff;
}

.fn-delete:active {
  transform: scale(0.95);
}

.add-function-btn {
  width: 100%;
  padding: 12px;
  margin-top: 8px;
  background: var(--key);
  border: 2px dashed var(--border);
  border-radius: 10px;
  color: var(--text);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
}

.add-function-btn:hover:not(:disabled) {
  background: var(--hover);
  border-color: var(--accent);
}

.add-function-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.templates-wrap {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.template-btn {
  background: var(--key);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px 14px;
  font-size: 13px;
  color: var(--text);
  cursor: pointer;
  transition: background 0.15s, transform 0.1s, box-shadow 0.15s;
  min-height: 36px;
  font-weight: 500;
}

.template-btn:hover {
  background: var(--hover);
  transform: translateY(-1px);
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.1);
}

.template-btn:active {
  transform: translateY(0);
}

.range-row {
  display: flex;
  gap: 8px;
  margin-bottom: 8px;
  flex-wrap: wrap;
}

.range-row label {
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--muted);
  font-size: 13px;
  flex: 1;
  min-width: 140px;
}

.range-row input {
  background: var(--display-bg);
  border: 1.5px solid var(--key);
  border-radius: 8px;
  padding: 8px 10px;
  color: var(--text);
  font-family: inherit;
  font-size: 16px; /* prevent iOS zoom on focus */
  width: 80px;
  outline: none;
  transition: border-color 0.15s, box-shadow 0.15s;
}

.range-row input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

/* Section action buttons (Find Root, Integrate, Extrema, ...).
   Scoped with :where() so the selector keeps its original specificity while
   skipping the controls that carry their own styling — function-row buttons
   (.fn-swatch/.fn-toggle/.fn-delete) and template pills. Without this, the
   `width: 100%` here outranked `.fn-swatch { width: 28px }` and stretched
   every inline control across the whole column. */
.graph-controls :where(button:not(.fn-swatch):not(.fn-toggle):not(.fn-delete):not(.template-btn):not(.add-function-btn)) {
  background: var(--accent);
  color: var(--accent-text);
  border: none;
  border-radius: 10px;
  padding: 12px 16px;
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: filter 0.15s, transform 0.1s, box-shadow 0.15s;
  width: 100%;
  margin-top: 8px;
  min-height: 44px;
  box-shadow: 0 2px 6px rgba(99, 102, 241, 0.25);
}

.graph-controls :where(button:not(.fn-swatch):not(.fn-toggle):not(.fn-delete):not(.template-btn):not(.add-function-btn)):hover {
  filter: brightness(1.1);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(99, 102, 241, 0.35);
}

.graph-controls :where(button:not(.fn-swatch):not(.fn-toggle):not(.fn-delete):not(.template-btn):not(.add-function-btn)):active {
  transform: translateY(0);
}

.integrate-row {
  display: flex;
  gap: 8px;
  margin-bottom: 8px;
  flex-wrap: wrap;
}

.integrate-row label {
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--muted);
  font-size: 13px;
  flex: 1;
  min-width: 140px;
}

.integrate-row input {
  background: var(--display-bg);
  border: 1.5px solid var(--key);
  border-radius: 8px;
  padding: 8px 10px;
  color: var(--text);
  font-family: inherit;
  font-size: 16px; /* prevent iOS zoom on focus */
  width: 80px;
  outline: none;
  transition: border-color 0.15s, box-shadow 0.15s;
}

.integrate-row input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

.result {
  margin-top: 8px;
  padding: 10px 14px;
  border-radius: 10px;
  font-family: 'Consolas', 'Monaco', monospace;
  font-size: 13px;
  min-height: 40px;
  display: flex;
  align-items: center;
  font-weight: 500;
}

.result.ok {
  background: rgba(74, 222, 128, 0.12);
  color: #4ade80;
  border: 1px solid rgba(74, 222, 128, 0.25);
}

.result.error {
  background: rgba(248, 113, 113, 0.12);
  color: #f87171;
  border: 1px solid rgba(248, 113, 113, 0.25);
}

/* ---------------- narrow screens: stack extended modes vertically ---------------- */
@media (max-width: 720px) {
  /* Comfortable touch targets for the toolbar (desktop sizing is compact). */
  .tool { min-width: 40px; height: 40px; font-size: 15px; }
  .toolbar { gap: 7px; }
  .tool-group { gap: 7px; }
  .tool-group + .tool-group { margin-left: 3px; padding-left: 10px; }

  .calculator.sci-on { max-width: 420px; }
  .calculator.sci-on #calculator-view { display: block; }
  .calculator.sci-on #sci-pad {
    grid-template-columns: repeat(3, 1fr);
    margin-bottom: 10px;
  }

  .calculator.graph-on { max-width: 420px; }
  #graph-view { display: flex; flex-direction: column; }
  #graph-view > .graph-controls {
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    max-height: none;
    overflow: visible;
    padding-right: 0;
  }
}

/* ---------------- small screens ---------------- */
@media (max-width: 400px) {
  .calculator { padding: 14px; border-radius: 16px; }
  .pad button { padding: 14px 0; font-size: 18px; }
  .current { font-size: 34px; }
  .graph-controls { grid-template-columns: 1fr; }
  .pad.sci { grid-template-columns: repeat(3, 1fr); }
  .pad.sci button.fn { padding: 12px 0; font-size: 14px; }
}

/* ---------------- very small screens ---------------- */
@media (max-width: 340px) {
  .calculator { padding: 10px; }
  .pad button { padding: 12px 0; font-size: 16px; }
  .current { font-size: 28px; }
}

/* ============================================================
   ROBOTIC / FUTURISTIC THEME — component styling
   ============================================================
   Two constraints shaped this block:

   1. Every colour here comes from a custom property, so the global
      [data-hc="on"] high-contrast override still wins on top of it
      (that block sits earlier in the file and shares specificity).
   2. clip-path and box-shadow are mutually exclusive: a clipped
      element's outer shadow is discarded. Glowing chamfered elements
      therefore use filter: drop-shadow(), which follows the clip.
   ============================================================ */

[data-theme="robot"] body {
  font-family: var(--r-font);
  background-color: var(--page-grad-1);
  background-image:
    linear-gradient(rgba(0, 217, 255, 0.05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0, 217, 255, 0.05) 1px, transparent 1px),
    radial-gradient(ellipse at 50% -10%, rgba(0, 217, 255, 0.14), transparent 62%),
    linear-gradient(165deg, var(--page-grad-1) 0%, var(--page-grad-2) 100%);
  background-size: 26px 26px, 26px 26px, 100% 100%, 100% 100%;
  background-attachment: fixed;
}

/* CRT scanlines over the whole viewport. Above every panel so the effect is
   uniform; pointer-events:none keeps the UI fully interactive. */
[data-theme="robot"] body::after {
  content: '';
  position: fixed;
  inset: 0;
  z-index: 9999;
  pointer-events: none;
  background: repeating-linear-gradient(
    to bottom,
    rgba(0, 0, 0, 0) 0 2px,
    rgba(0, 0, 0, 0.13) 2px 4px
  );
}

/* Card: near-square corners plus four corner brackets drawn as background
   gradients, which avoids extra DOM and survives the clip. */
[data-theme="robot"] .calculator {
  border-radius: 2px;
  border: 1px solid var(--border);
  background-color: var(--card);
  background-image:
    linear-gradient(var(--r-cyan), var(--r-cyan)),
    linear-gradient(var(--r-cyan), var(--r-cyan)),
    linear-gradient(var(--r-cyan), var(--r-cyan)),
    linear-gradient(var(--r-cyan), var(--r-cyan)),
    linear-gradient(var(--r-cyan), var(--r-cyan)),
    linear-gradient(var(--r-cyan), var(--r-cyan)),
    linear-gradient(var(--r-cyan), var(--r-cyan)),
    linear-gradient(var(--r-cyan), var(--r-cyan)),
    linear-gradient(180deg, rgba(0, 217, 255, 0.07), transparent 32%);
  background-repeat: no-repeat;
  background-position:
    top left, top left, top right, top right,
    bottom left, bottom left, bottom right, bottom right,
    0 0;
  background-size:
    16px 1px, 1px 16px, 16px 1px, 1px 16px,
    16px 1px, 1px 16px, 16px 1px, 1px 16px,
    100% 100%;
  box-shadow:
    inset 0 0 46px rgba(0, 0, 0, 0.55),
    0 0 22px rgba(0, 217, 255, 0.10),
    0 18px 50px var(--shadow);
}

/* ---------------- toolbar ---------------- */
[data-theme="robot"] .tool {
  clip-path: var(--r-chamfer-sm);
  border: 1px solid var(--border);
  background: var(--key);
  font-family: var(--r-font);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

[data-theme="robot"] .tool:hover {
  filter: none;
  color: var(--r-cyan);
  border-color: var(--r-cyan);
}

[data-theme="robot"] .tool[aria-pressed="true"] {
  background: var(--op);
  color: var(--op-text);
  border-color: var(--r-cyan);
  box-shadow: inset 0 0 12px rgba(0, 217, 255, 0.30);
}

[data-theme="robot"] .tool-group + .tool-group {
  border-left: 1px dashed var(--border);
}

/* The key-size button reads as a text glyph; uppercasing turns "Aa" into "AA",
   which loses its meaning. */
[data-theme="robot"] #btn-density { text-transform: none; }

/* ---------------- display ---------------- */
[data-theme="robot"] .display {
  position: relative;
  border: 1px solid var(--border);
  border-radius: 2px;
  background-color: var(--display-bg);
  background-image: linear-gradient(180deg, rgba(0, 217, 255, 0.06), transparent 45%);
  box-shadow: inset 0 0 26px rgba(0, 217, 255, 0.10);
  overflow: hidden;
}

/* Slow sweep, like a refreshing readout. */
[data-theme="robot"] .display::after {
  content: '';
  position: absolute;
  left: 0;
  right: 0;
  top: -45%;
  height: 45%;
  background: linear-gradient(180deg, transparent, rgba(0, 217, 255, 0.12), transparent);
  animation: robot-sweep 7s linear infinite;
  pointer-events: none;
}

@keyframes robot-sweep {
  to { top: 105%; }
}

[data-theme="robot"] .current {
  font-family: var(--r-font);
  font-weight: 500;
  color: var(--text);
  text-shadow: 0 0 12px rgba(0, 217, 255, 0.45);
  letter-spacing: 0.02em;
}

[data-theme="robot"] .history-line {
  font-family: var(--r-font);
  font-size: 13px;
  color: var(--muted);
}

[data-theme="robot"] .mem-badge {
  clip-path: var(--r-chamfer-sm);
  border-radius: 0;
  background: var(--r-amber);
  color: #20140a;
  font-family: var(--r-font);
}

/* ---------------- keys ---------------- */
[data-theme="robot"] .pad button {
  clip-path: var(--r-chamfer);
  border: 1px solid var(--border);
  background-color: var(--key);
  background-image: linear-gradient(180deg, rgba(255, 255, 255, 0.06), transparent 55%);
  color: var(--key-text);
  font-family: var(--r-font);
  letter-spacing: 0.02em;
}

[data-theme="robot"] .pad button:hover {
  filter: drop-shadow(0 0 7px rgba(0, 217, 255, 0.50));
  border-color: var(--r-cyan);
  color: #ffffff;
}

[data-theme="robot"] .pad button:active { filter: brightness(1.35); }

[data-theme="robot"] .pad button.op {
  background-color: var(--op);
  background-image: linear-gradient(180deg, rgba(0, 217, 255, 0.16), transparent 60%);
  color: var(--op-text);
}

[data-theme="robot"] .pad button.equals {
  background-color: var(--r-amber);
  background-image: linear-gradient(180deg, rgba(255, 255, 255, 0.30), transparent 65%);
  border-color: var(--r-amber);
  color: #1c1206;
  font-weight: 700;
}

[data-theme="robot"] .pad button.equals:hover {
  filter: drop-shadow(0 0 10px rgba(255, 176, 32, 0.75));
  border-color: #ffd27a;
}

[data-theme="robot"] .pad button.danger {
  background-color: var(--danger);
  border-color: var(--danger);
  color: #ffffff;
}

[data-theme="robot"] .pad.sci button.fn {
  background-color: var(--fn);
  background-image: linear-gradient(180deg, rgba(70, 224, 200, 0.16), transparent 60%);
  color: var(--fn-text);
}

/* Transparent border keeps the row from shifting when the key lights up. */
[data-theme="robot"] .pad.memory button.mem {
  clip-path: var(--r-chamfer-sm);
  border: 1px solid transparent;
  background: transparent;
  color: var(--muted);
  font-family: var(--r-font);
}

[data-theme="robot"] .pad.memory button.mem:hover {
  background: var(--key);
  border-color: var(--border);
  color: var(--op-text);
}

/* ---------------- inputs & selects ---------------- */
[data-theme="robot"] .fn-text,
[data-theme="robot"] .fn-mode,
[data-theme="robot"] .fn-t,
[data-theme="robot"] .table-step-label input,
[data-theme="robot"] .range-row input,
[data-theme="robot"] .integrate-row input {
  border-radius: 2px;
  border: 1px solid var(--border);
  background-color: var(--display-bg);
  color: var(--text);
  font-family: var(--r-font);
}

[data-theme="robot"] .fn-text:focus,
[data-theme="robot"] .fn-mode:focus,
[data-theme="robot"] .fn-t:focus,
[data-theme="robot"] .table-step-label input:focus,
[data-theme="robot"] .range-row input:focus,
[data-theme="robot"] .integrate-row input:focus {
  border-color: var(--r-cyan);
  box-shadow: 0 0 0 1px var(--r-cyan), 0 0 14px rgba(0, 217, 255, 0.30);
  outline: none;
}

/* Native dropdown lists render with OS colours unless told otherwise. */
[data-theme="robot"] .fn-mode option,
[data-theme="robot"] .fn-text option {
  background: var(--card);
  color: var(--text);
}

[data-theme="robot"] .fn-input-row {
  border: 1px solid transparent;
  background: var(--display-bg);
}

[data-theme="robot"] .fn-input-row:hover {
  border-color: var(--border);
  background: var(--hover);
}

/* ---------------- panels ---------------- */
[data-theme="robot"] .history-panel,
[data-theme="robot"] .table-panel {
  border-radius: 2px;
  border: 1px solid var(--border);
  background: var(--panel);
  box-shadow: inset 0 0 30px rgba(0, 0, 0, 0.45), 0 10px 40px var(--shadow);
}

[data-theme="robot"] .history-head {
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border);
  font-family: var(--r-font);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 14px;
}

[data-theme="robot"] .history-head button {
  clip-path: var(--r-chamfer-sm);
  border: 1px solid var(--border);
  border-radius: 0;
  background: var(--key);
  color: var(--muted);
  font-family: var(--r-font);
  text-transform: uppercase;
  /* Uppercase plus letter-spacing makes these labels wider than the flex row
     can spare, and shrink was wrapping "← Back" onto two lines. */
  white-space: nowrap;
  flex: 0 0 auto;
}

[data-theme="robot"] .history-head .back {
  background: var(--op);
  color: var(--op-text);
  border-color: var(--r-cyan);
  font-weight: 700;
}

[data-theme="robot"] .history-item {
  border-radius: 2px;
  border: 1px solid transparent;
  font-family: var(--r-font);
}

[data-theme="robot"] .history-item:hover {
  background: var(--hover);
  border-color: var(--border);
}

[data-theme="robot"] .history-item .res {
  color: var(--text);
  text-shadow: 0 0 10px rgba(0, 217, 255, 0.30);
}

[data-theme="robot"] #values-table th {
  background: var(--key);
  color: var(--op-text);
  font-family: var(--r-font);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* ---------------- converter ---------------- */
[data-theme="robot"] .convert-result {
  clip-path: var(--r-chamfer-sm);
  border-radius: 0;
  border: 1px solid var(--r-cyan);
  background: var(--op);
  color: var(--op-text);
  font-family: var(--r-font);
  text-shadow: 0 0 10px rgba(0, 217, 255, 0.45);
}

[data-theme="robot"] .convert-swap {
  border-radius: 0;
  clip-path: polygon(50% 0, 100% 25%, 100% 75%, 50% 100%, 0 75%, 0 25%);
  border: 1px solid var(--r-cyan);
  background: var(--op);
  color: var(--op-text);
}

[data-theme="robot"] .convert-swap:hover {
  background: var(--hover);
  filter: drop-shadow(0 0 8px rgba(0, 217, 255, 0.6));
}

[data-theme="robot"] .convert-hint {
  background: var(--display-bg);
  border-left: 2px solid var(--r-amber);
  color: var(--op-text);
  font-family: var(--r-font);
}

[data-theme="robot"] .fx-status {
  border-radius: 2px;
  border: 1px solid var(--border);
  background: var(--display-bg);
  font-family: var(--r-font);
}

[data-theme="robot"] .fx-refresh {
  border-radius: 0;
  clip-path: var(--r-chamfer-sm);
  border: 1px solid var(--r-cyan);
  color: var(--r-cyan);
  font-family: var(--r-font);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* ---------------- symbolic solver ---------------- */
[data-theme="robot"] .cas-go {
  clip-path: var(--r-chamfer-sm);
  border-radius: 0;
  border: 1px solid var(--r-cyan);
  background: var(--accent);
  font-family: var(--r-font);
  text-transform: uppercase;
  letter-spacing: 0.10em;
}

[data-theme="robot"] .cas-go:hover {
  filter: drop-shadow(0 0 10px rgba(0, 217, 255, 0.55));
}

[data-theme="robot"] .cas-example {
  clip-path: var(--r-chamfer-sm);
  border-radius: 0;
  background: var(--key);
  font-family: var(--r-font);
}

[data-theme="robot"] .cas-example:hover {
  background: var(--hover);
  color: var(--r-cyan);
}

[data-theme="robot"] .cas-result {
  border-radius: 2px;
  border: 1px solid var(--border);
  background: var(--display-bg);
}

[data-theme="robot"] .cas-label {
  font-family: var(--r-font);
  color: var(--r-cyan);
  letter-spacing: 0.12em;
}

/* Math stays in a serif face: it aids reading of fractions and exponents,
   which a monospace grid would make harder to scan. */
[data-theme="robot"] .cas-value {
  color: var(--text);
  text-shadow: 0 0 12px rgba(0, 217, 255, 0.25);
}

[data-theme="robot"] .cas-note {
  font-family: var(--r-font);
}

[data-theme="robot"] .cas-note::before {
  content: '\25B8';
  color: var(--r-amber);
}

/* ---------------- graph view ---------------- */
[data-theme="robot"] #graph-view .toolbar button {
  clip-path: var(--r-chamfer-sm);
  border: 1px solid var(--border);
  border-radius: 0;
  background: var(--key);
  color: var(--muted);
  font-family: var(--r-font);
}

[data-theme="robot"] #graph-view .toolbar button:hover {
  filter: none;
  color: var(--r-cyan);
  border-color: var(--r-cyan);
}

[data-theme="robot"] #graph-view .toolbar .back {
  background: var(--op);
  color: var(--op-text);
  border-color: var(--r-cyan);
  font-weight: 700;
}

[data-theme="robot"] .graph-title {
  font-family: var(--r-font);
  text-transform: uppercase;
  letter-spacing: 0.10em;
  font-size: 15px;
  color: var(--r-cyan);
  text-shadow: 0 0 12px rgba(0, 217, 255, 0.35);
}

[data-theme="robot"] .graph-canvas-wrap {
  border: 1px solid var(--border);
  border-radius: 2px;
  background: var(--display-bg);
  box-shadow: inset 0 0 30px rgba(0, 0, 0, 0.6);
}

[data-theme="robot"] #graph-canvas {
  border-radius: 0;
}

[data-theme="robot"] .graph-section {
  border-radius: 2px;
  border: 1px solid var(--border);
  background: var(--panel);
  box-shadow: inset 0 0 24px rgba(0, 0, 0, 0.4);
}

[data-theme="robot"] .graph-section h3 {
  font-family: var(--r-font);
  color: var(--r-cyan);
  letter-spacing: 0.14em;
  border-bottom: 1px solid var(--border);
  padding-bottom: 8px;
}

[data-theme="robot"] .graph-section h3::before {
  width: 10px;
  height: 10px;
  background: var(--r-amber);
  border-radius: 0;
  clip-path: polygon(50% 0, 100% 50%, 50% 100%, 0 50%);
}

[data-theme="robot"] .fn-toggle,
[data-theme="robot"] .fn-delete,
[data-theme="robot"] .add-function-btn,
[data-theme="robot"] .template-btn {
  clip-path: var(--r-chamfer-sm);
  border-radius: 0;
  font-family: var(--r-font);
}

[data-theme="robot"] .fn-toggle {
  border: 1px solid var(--border);
  background: var(--key);
}

[data-theme="robot"] .fn-toggle:hover {
  filter: none;
  border-color: var(--r-cyan);
  color: var(--r-cyan);
}

[data-theme="robot"] .fn-delete {
  border: 1px solid var(--danger);
  background: transparent;
}

[data-theme="robot"] .add-function-btn {
  border: 1px dashed var(--border);
  background: transparent;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

[data-theme="robot"] .add-function-btn:hover:not(:disabled) {
  border-color: var(--r-cyan);
  color: var(--r-cyan);
  background: var(--key);
}

[data-theme="robot"] .template-btn {
  border: 1px solid var(--border);
  background: var(--key);
}

[data-theme="robot"] .template-btn:hover {
  border-color: var(--r-cyan);
  color: var(--r-cyan);
}

/* Section action buttons (Find Root, Integrate, ...). */
[data-theme="robot"] .graph-controls :where(button:not(.fn-swatch):not(.fn-toggle):not(.fn-delete):not(.template-btn):not(.add-function-btn)) {
  clip-path: var(--r-chamfer-sm);
  border: 1px solid var(--r-cyan);
  border-radius: 0;
  background: var(--op);
  color: var(--op-text);
  font-family: var(--r-font);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  box-shadow: none;
}

[data-theme="robot"] .graph-controls :where(button:not(.fn-swatch):not(.fn-toggle):not(.fn-delete):not(.template-btn):not(.add-function-btn)):hover {
  filter: drop-shadow(0 0 9px rgba(0, 217, 255, 0.55));
  transform: none;
}

[data-theme="robot"] .result {
  border-radius: 2px;
  font-family: var(--r-font);
}

/* ---------------- scrollbars ---------------- */
[data-theme="robot"] ::-webkit-scrollbar { width: 10px; height: 10px; }
[data-theme="robot"] ::-webkit-scrollbar-track { background: var(--display-bg); }
[data-theme="robot"] ::-webkit-scrollbar-thumb {
  background: var(--op);
  border: 1px solid var(--border);
}
[data-theme="robot"] ::-webkit-scrollbar-thumb:hover { background: var(--accent); }

[data-theme="robot"] {
  scrollbar-color: var(--accent) var(--display-bg);
  scrollbar-width: thin;
}

/* ---------------- motion preferences ---------------- */
@media (prefers-reduced-motion: reduce) {
  [data-theme="robot"] .display::after { animation: none; display: none; }
  [data-theme="robot"] .pad button:active,
  [data-theme="robot"] .template-btn:hover { transform: none; }
}