:root {
  color-scheme: dark;
  --bg: #070a12;
  --card: rgba(17, 23, 39, 0.86);
  --card-strong: rgba(25, 34, 57, 0.94);
  --screen: #101724;
  --screen-deep: #0a0f19;
  --text: #f5f7fb;
  --muted: #98a6bd;
  --accent: #67e8f9;
  --accent-2: #a78bfa;
  --danger: #fb7185;
  --button: #1c2638;
  --button-hover: #26344c;
  --button-active: #334461;
  --operator: #263d63;
  --operator-hover: #31527f;
  --utility: #44253c;
  --utility-hover: #5b304d;
  --equals: #0f766e;
  --equals-hover: #0d9488;
  --memory: #3b2f66;
  --scientific: #27304b;
  --shadow: 0 24px 70px rgba(0, 0, 0, 0.48);
  --radius-xl: 32px;
  --radius-lg: 22px;
  --radius-md: 16px;
  --button-size: 72px;
  --font: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font);
  background:
    radial-gradient(circle at 18% 16%, rgba(103, 232, 249, 0.18), transparent 28%),
    radial-gradient(circle at 86% 8%, rgba(167, 139, 250, 0.18), transparent 32%),
    linear-gradient(135deg, #05070d 0%, #08111f 48%, #080912 100%);
  color: var(--text);
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  opacity: 0.18;
  background-image:
    linear-gradient(rgba(255, 255, 255, 0.05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.04) 1px, transparent 1px);
  background-size: 38px 38px;
  mask-image: radial-gradient(circle at center, black, transparent 72%);
}

button {
  font: inherit;
}

.app-shell {
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: clamp(18px, 4vw, 44px);
}

.calculator-card {
  width: min(100%, 520px);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-xl);
  padding: clamp(18px, 4vw, 28px);
  background:
    linear-gradient(150deg, rgba(255, 255, 255, 0.08), transparent 34%),
    var(--card);
  box-shadow: var(--shadow);
  backdrop-filter: blur(18px);
  overflow: hidden;
}

.calculator-card.advanced-active {
  width: min(100%, 720px);
  transition: width 260ms ease;
}

.brand-bar {
  display: flex;
  justify-content: space-between;
  gap: 18px;
  align-items: flex-start;
  margin-bottom: 18px;
}

.eyebrow {
  margin: 0 0 4px;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.16em;
  font-size: 0.72rem;
  font-weight: 800;
}

h1 {
  margin: 0;
  font-size: clamp(1.75rem, 4vw, 2.55rem);
  letter-spacing: -0.055em;
  line-height: 0.95;
}

.status-pill,
.hint-chip,
.memory-indicator {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  white-space: nowrap;
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 999px;
  padding: 8px 11px;
  color: var(--muted);
  background: rgba(255, 255, 255, 0.045);
  font-size: 0.78rem;
  font-weight: 700;
}

.status-dot {
  width: 8px;
  height: 8px;
  border-radius: 999px;
  background: #22c55e;
  box-shadow: 0 0 18px #22c55e;
}

.display-panel {
  border-radius: calc(var(--radius-xl) - 8px);
  padding: 18px;
  margin-bottom: 16px;
  background:
    linear-gradient(180deg, rgba(103, 232, 249, 0.07), transparent 36%),
    radial-gradient(circle at right top, rgba(167, 139, 250, 0.14), transparent 40%),
    var(--screen);
  border: 1px solid rgba(255, 255, 255, 0.08);
  box-shadow: inset 0 0 0 1px rgba(0, 0, 0, 0.24), inset 0 -22px 40px rgba(0, 0, 0, 0.2);
}

.mode-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  min-height: 28px;
  gap: 12px;
}

.mode-label {
  color: var(--muted);
  font-size: 0.78rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  font-weight: 800;
}

.memory-indicator {
  padding: 5px 8px;
  color: #c4b5fd;
  background: rgba(124, 58, 237, 0.14);
}

.expression-display {
  min-height: 54px;
  display: flex;
  justify-content: flex-end;
  align-items: flex-end;
  overflow-wrap: anywhere;
  text-align: right;
  font-size: clamp(2rem, 8vw, 3.6rem);
  letter-spacing: -0.05em;
  font-weight: 800;
  font-variant-numeric: tabular-nums;
}

.result-display {
  min-height: 24px;
  color: var(--muted);
  text-align: right;
  font-size: 0.95rem;
  font-variant-numeric: tabular-nums;
}

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

.toolbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  margin-bottom: 12px;
}

.advanced-toggle {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  border: 0;
  color: #071019;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  font-weight: 900;
  padding: 12px 16px;
  border-radius: 999px;
  cursor: pointer;
  box-shadow: 0 12px 30px rgba(103, 232, 249, 0.17);
  transition: transform 160ms ease, filter 160ms ease, box-shadow 160ms ease;
}

.advanced-toggle:hover {
  transform: translateY(-1px);
  filter: brightness(1.05);
  box-shadow: 0 16px 38px rgba(103, 232, 249, 0.23);
}

.advanced-toggle:active {
  transform: translateY(1px) scale(0.98);
}

.advanced-toggle[aria-expanded="true"] .toggle-icon {
  transform: rotate(180deg);
}

.toggle-icon {
  transition: transform 220ms ease;
}

.advanced-panel {
  display: grid;
  grid-template-rows: 0fr;
  opacity: 0;
  transition: grid-template-rows 280ms ease, opacity 240ms ease, margin 240ms ease;
  margin-bottom: 0;
}

.calculator-card.advanced-active .advanced-panel {
  grid-template-rows: 1fr;
  opacity: 1;
  margin-bottom: 12px;
}

.advanced-grid {
  overflow: hidden;
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 10px;
  padding: 0;
}

.basic-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  grid-auto-rows: var(--button-size);
  gap: 12px;
}

.calc-button {
  position: relative;
  min-height: 54px;
  border: 1px solid rgba(255, 255, 255, 0.09);
  border-radius: var(--radius-md);
  color: var(--text);
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.08), transparent 65%),
    var(--button);
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.24);
  cursor: pointer;
  user-select: none;
  font-size: 1.15rem;
  font-weight: 850;
  transition: transform 120ms ease, background 160ms ease, box-shadow 160ms ease, border-color 160ms ease;
  -webkit-tap-highlight-color: transparent;
}

.calc-button:hover {
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.1), transparent 65%),
    var(--button-hover);
  border-color: rgba(255, 255, 255, 0.16);
  transform: translateY(-1px);
}

.calc-button:active,
.calc-button.pressed {
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.08), transparent 65%),
    var(--button-active);
  transform: translateY(1px) scale(0.985);
  box-shadow: 0 6px 14px rgba(0, 0, 0, 0.22);
}

.calc-button.operator {
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.08), transparent 65%),
    var(--operator);
}

.calc-button.operator:hover {
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.1), transparent 65%),
    var(--operator-hover);
}

.calc-button.utility {
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.08), transparent 65%),
    var(--utility);
}

.calc-button.utility:hover {
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.1), transparent 65%),
    var(--utility-hover);
}

.calc-button.equals {
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.16), transparent 72%),
    var(--equals);
}

.calc-button.equals:hover {
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.18), transparent 72%),
    var(--equals-hover);
}

.calc-button.scientific {
  min-height: 48px;
  border-radius: 14px;
  color: #dbeafe;
  background:
    linear-gradient(180deg, rgba(103, 232, 249, 0.08), transparent 68%),
    var(--scientific);
  font-size: 0.95rem;
}

.calc-button.memory {
  min-height: 48px;
  border-radius: 14px;
  color: #ddd6fe;
  background:
    linear-gradient(180deg, rgba(167, 139, 250, 0.1), transparent 68%),
    var(--memory);
  font-size: 0.92rem;
}

.calc-button.ghosted {
  color: rgba(255, 255, 255, 0.42);
  cursor: default;
}

.calc-button.ghosted:hover,
.calc-button.ghosted:active {
  transform: none;
  background:
    linear-gradient(180deg, rgba(103, 232, 249, 0.08), transparent 68%),
    var(--scientific);
}

.zero {
  grid-column: span 2;
}

.tall {
  grid-row: span 2;
}

.footer-note {
  display: flex;
  justify-content: space-between;
  gap: 10px;
  margin-top: 14px;
  color: rgba(245, 247, 251, 0.54);
  font-size: 0.78rem;
  font-weight: 700;
}

.footer-note span:first-child {
  color: rgba(103, 232, 249, 0.74);
}

@media (max-width: 640px) {
  :root {
    --button-size: 64px;
  }

  .app-shell {
    align-items: stretch;
    padding: 12px;
  }

  .calculator-card,
  .calculator-card.advanced-active {
    width: 100%;
    border-radius: 24px;
    padding: 16px;
  }

  .brand-bar {
    flex-direction: column;
    gap: 12px;
  }

  .status-pill {
    align-self: flex-start;
  }

  .advanced-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .basic-grid {
    gap: 10px;
  }

  .calc-button {
    border-radius: 15px;
    font-size: 1.05rem;
  }

  .calc-button.scientific,
  .calc-button.memory {
    min-height: 46px;
    font-size: 0.88rem;
  }

  .footer-note {
    flex-direction: column;
  }
}

@media (max-width: 380px) {
  :root {
    --button-size: 58px;
  }

  .advanced-grid {
    gap: 8px;
  }

  .basic-grid {
    gap: 8px;
  }

  .calc-button.scientific,
  .calc-button.memory {
    font-size: 0.82rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
  }
}