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

:root {
  --bg: #070708;
  --ink: #f4f1ec;
  --muted: rgba(244, 241, 236, 0.55);
  --faint: rgba(244, 241, 236, 0.22);
  --line: rgba(255, 255, 255, 0.09);
  --panel: rgba(14, 14, 16, 0.82);
  --accent: #e8b86d;
  --accent-2: #7b9cff;
  --accent-3: #6fd3a3;
  --danger: #e07a5f;
  --eq: #c9a45c;
  --serif: "Instrument Serif", Georgia, serif;
  --sans: Inter, system-ui, sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, Consolas, monospace;
}

html, body {
  min-height: 100%;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  -webkit-font-smoothing: antialiased;
}

body { overflow-x: hidden; }

.bg {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background:
    radial-gradient(ellipse 70% 50% at 20% 0%, rgba(232, 184, 109, 0.08), transparent 55%),
    radial-gradient(ellipse 60% 45% at 90% 20%, rgba(123, 156, 255, 0.07), transparent 50%),
    linear-gradient(180deg, #0b0b0d 0%, #070708 100%),
    repeating-linear-gradient(0deg, transparent, transparent 47px, rgba(255,255,255,0.02) 48px),
    repeating-linear-gradient(90deg, transparent, transparent 47px, rgba(255,255,255,0.02) 48px);
}

.top {
  position: relative;
  z-index: 10;
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 10px 14px;
  padding: 18px 22px 8px;
}

.brand {
  font-size: 12px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
  text-decoration: none;
  border-bottom: 1px solid transparent;
}
.brand:hover { color: var(--ink); border-color: var(--faint); }
.sep { color: var(--faint); font-size: 12px; }
.top h1 {
  font-family: var(--serif);
  font-weight: 400;
  font-size: 24px;
  letter-spacing: -0.02em;
}

.modes {
  display: inline-flex;
  gap: 4px;
  margin-left: 8px;
  padding: 3px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: rgba(255,255,255,0.03);
}
.mode {
  appearance: none;
  border: 0;
  background: transparent;
  color: var(--muted);
  font: 500 12px/1 var(--sans);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 8px 14px;
  border-radius: 999px;
  cursor: pointer;
}
.mode.active {
  background: rgba(232, 184, 109, 0.16);
  color: var(--ink);
}

.top-actions {
  margin-left: auto;
  display: flex;
  gap: 8px;
}

.ghost {
  appearance: none;
  border: 1px solid var(--line);
  background: rgba(255,255,255,0.03);
  color: var(--muted);
  font: 500 11px/1 var(--sans);
  letter-spacing: 0.05em;
  text-transform: uppercase;
  padding: 8px 12px;
  border-radius: 999px;
  cursor: pointer;
  transition: color 160ms ease, border-color 160ms ease, background 160ms ease;
}
.ghost:hover, .ghost.active {
  color: var(--ink);
  border-color: rgba(255,255,255,0.22);
}
.ghost.active {
  background: rgba(232, 184, 109, 0.14);
  border-color: rgba(232, 184, 109, 0.35);
  color: var(--accent);
}
.ghost:disabled {
  opacity: 0.55;
  cursor: default;
}

.shell {
  position: relative;
  z-index: 1;
  max-width: 1180px;
  margin: 0 auto;
  padding: 12px 18px 40px;
}

.panel[hidden] { display: none !important; }

/* ——— Calc ——— */
.calc-panel {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 240px;
  gap: 18px;
  align-items: start;
}

.display {
  grid-column: 1 / 2;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 18px;
  padding: 16px 18px 14px;
  backdrop-filter: blur(12px);
  min-height: 148px;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.history {
  min-height: 48px;
  max-height: 96px;
  overflow-y: auto;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--muted);
  line-height: 1.55;
}
.history .h-row {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  cursor: pointer;
  padding: 2px 0;
  border-bottom: 1px solid transparent;
}
.history .h-row:hover { color: var(--ink); border-bottom-color: var(--line); }
.history .h-res { color: var(--accent); }

.expr {
  font-family: var(--mono);
  font-size: clamp(18px, 2.4vw, 22px);
  font-weight: 500;
  min-height: 1.4em;
  outline: none;
  word-break: break-all;
  caret-color: var(--accent);
  white-space: pre-wrap;
}
.expr:empty::before {
  content: "expression…";
  color: var(--faint);
}

.result {
  font-family: var(--serif);
  font-size: clamp(36px, 6vw, 52px);
  letter-spacing: -0.03em;
  text-align: right;
  line-height: 1.05;
  color: var(--ink);
  margin-top: auto;
}
.result.error { color: var(--danger); font-size: clamp(18px, 3vw, 24px); font-family: var(--sans); }

.keypad {
  grid-column: 1 / 2;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.pad-row {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 6px;
}
.pad-row.fn button {
  font-size: 12px;
  letter-spacing: 0.02em;
  padding: 10px 4px;
  color: var(--muted);
  background: rgba(255,255,255,0.025);
}
.pad-row.fn button:hover { color: var(--accent-2); border-color: rgba(123,156,255,0.35); }

.pad-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 7px;
  margin-top: 4px;
}

.keypad button {
  appearance: none;
  border: 1px solid var(--line);
  background: rgba(255,255,255,0.04);
  color: var(--ink);
  font: 500 15px/1 var(--sans);
  border-radius: 12px;
  padding: 14px 6px;
  cursor: pointer;
  transition: transform 80ms ease, background 120ms ease, border-color 120ms ease, color 120ms ease;
  user-select: none;
}
.keypad button:hover {
  background: rgba(255,255,255,0.08);
  border-color: rgba(255,255,255,0.18);
}
.keypad button:active { transform: translateY(1px) scale(0.98); }
.keypad button.muted { color: var(--muted); }
.keypad button.op { color: var(--accent); font-size: 18px; }
.keypad button.eq {
  background: linear-gradient(180deg, rgba(232,184,109,0.28), rgba(232,184,109,0.12));
  border-color: rgba(232,184,109,0.45);
  color: #fff4df;
  font-weight: 600;
}
.keypad button.span2 { grid-column: span 2; }

.cheat {
  grid-column: 2 / 3;
  grid-row: 1 / 3;
  align-self: stretch;
  padding: 18px 16px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: rgba(255,255,255,0.02);
}
.cheat h2 {
  font-family: var(--serif);
  font-weight: 400;
  font-size: 22px;
  margin-bottom: 8px;
}
.cheat p { font-size: 13px; color: var(--muted); margin-bottom: 14px; line-height: 1.45; }
.cheat ul { list-style: none; display: flex; flex-direction: column; gap: 8px; }
.cheat code {
  display: block;
  font-family: var(--mono);
  font-size: 11px;
  color: rgba(244,241,236,0.72);
  line-height: 1.45;
  word-break: break-word;
}
.cheat .hint { margin-top: 18px; font-size: 11px; letter-spacing: 0.04em; text-transform: uppercase; color: var(--faint); }

/* ——— Graph ——— */
.graph-panel {
  display: grid;
  grid-template-columns: 300px minmax(0, 1fr);
  gap: 14px;
  min-height: calc(100vh - 96px);
}

.graph-side {
  display: flex;
  flex-direction: column;
  gap: 12px;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--panel);
  backdrop-filter: blur(12px);
}

.g-mode { display: flex; flex-wrap: wrap; gap: 6px; }
.chip {
  appearance: none;
  border: 1px solid var(--line);
  background: transparent;
  color: var(--muted);
  font: 500 11px/1 var(--sans);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  padding: 7px 10px;
  border-radius: 999px;
  cursor: pointer;
}
.chip.active {
  color: var(--ink);
  border-color: rgba(123,156,255,0.4);
  background: rgba(123,156,255,0.12);
}

.curves { display: flex; flex-direction: column; gap: 10px; }

.curve {
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 10px;
  background: rgba(0,0,0,0.2);
}
.curve-head {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 8px;
}
.swatch {
  width: 12px; height: 12px;
  border-radius: 50%;
  flex: 0 0 auto;
  box-shadow: 0 0 0 2px rgba(255,255,255,0.08);
}
.curve-head label {
  flex: 1;
  font-size: 11px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--muted);
}
.curve-head .rm {
  appearance: none;
  border: 0;
  background: transparent;
  color: var(--faint);
  cursor: pointer;
  font-size: 14px;
  padding: 2px 6px;
}
.curve-head .rm:hover { color: var(--danger); }
.curve input[type="text"] {
  width: 100%;
  appearance: none;
  border: 1px solid var(--line);
  background: rgba(255,255,255,0.03);
  color: var(--ink);
  font: 500 13px/1.3 var(--mono);
  padding: 8px 10px;
  border-radius: 10px;
  outline: none;
  margin-bottom: 6px;
}
.curve input[type="text"]:focus { border-color: rgba(232,184,109,0.45); }
.curve .err {
  font-size: 11px;
  color: var(--danger);
  min-height: 14px;
}

.add-curve { align-self: flex-start; }

.range-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}
.range-grid label {
  display: flex;
  flex-direction: column;
  gap: 4px;
  font-size: 10px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--faint);
}
.range-grid input {
  appearance: none;
  border: 1px solid var(--line);
  background: rgba(255,255,255,0.03);
  color: var(--ink);
  font: 500 13px/1 var(--mono);
  padding: 8px 10px;
  border-radius: 10px;
  outline: none;
  width: 100%;
}
.range-grid[hidden], .param-only[hidden] { display: none !important; }

.presets {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  align-items: center;
}
.presets > span {
  width: 100%;
  font-size: 10px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--faint);
}
.presets button {
  appearance: none;
  border: 1px solid var(--line);
  background: transparent;
  color: var(--muted);
  font: 500 11px/1 var(--sans);
  padding: 6px 9px;
  border-radius: 8px;
  cursor: pointer;
}
.presets button:hover { color: var(--ink); border-color: rgba(255,255,255,0.2); }

.g-actions { display: flex; flex-wrap: wrap; gap: 6px; }
.graph-side .hint {
  font-size: 11px;
  color: var(--faint);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.canvas-wrap {
  position: relative;
  border: 1px solid var(--line);
  border-radius: 18px;
  overflow: hidden;
  background:
    radial-gradient(ellipse 80% 70% at 50% 40%, #12131a 0%, #09090b 100%);
  min-height: 520px;
}
#plot {
  display: block;
  width: 100%;
  height: 100%;
  cursor: crosshair;
  touch-action: none;
}

.trace {
  position: absolute;
  pointer-events: none;
  font: 500 11px/1.35 var(--mono);
  color: var(--ink);
  background: rgba(8,8,10,0.88);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 8px 10px;
  backdrop-filter: blur(8px);
  white-space: pre;
  z-index: 2;
  transform: translate(12px, 12px);
}

@media (max-width: 900px) {
  .calc-panel { grid-template-columns: 1fr; }
  .cheat { grid-column: 1; grid-row: auto; order: 3; }
  .pad-row { grid-template-columns: repeat(3, 1fr); }
  .graph-panel { grid-template-columns: 1fr; }
  .canvas-wrap { min-height: 420px; }
  .top-actions { width: 100%; margin-left: 0; }
}