:root {
  --ink: #eaf1ff;
  --ink-soft: #aab9d4;
  --canvas: #09111f;
  --canvas-raised: #0f1b2e;
  --panel: #14233a;
  --panel-soft: #1b2e49;
  --line: rgba(176, 201, 235, 0.16);
  --line-strong: rgba(176, 201, 235, 0.3);
  --blue: #8bb8ff;
  --blue-strong: #4e8ff3;
  --cyan: #6ee7d4;
  --shadow: 0 24px 80px rgba(0, 0, 0, 0.28);
}

* {
  box-sizing: border-box;
}

body {
  min-width: 320px;
  min-height: 100vh;
  margin: 0;
  color: var(--ink);
  background:
    radial-gradient(circle at 78% 12%, rgba(78, 143, 243, 0.17), transparent 32rem),
    radial-gradient(circle at 14% 82%, rgba(110, 231, 212, 0.08), transparent 26rem),
    var(--canvas);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.5;
}

button,
a {
  -webkit-tap-highlight-color: transparent;
}

button {
  font: inherit;
}

.app-shell {
  width: min(540px, calc(100% - 40px));
  margin: 0 auto;
  padding: 40px 0 56px;
}

.site-header,
.calculator-header,
.result-line,
.status-chip,
.division-note,
.scope-item,
.next-step {
  display: flex;
  align-items: center;
}

.site-header {
  justify-content: space-between;
  gap: 24px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--ink);
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  text-decoration: none;
}

.brand-mark {
  display: grid;
  width: 30px;
  height: 30px;
  place-items: center;
  color: #07111f;
  background: var(--cyan);
  border-radius: 9px;
  font-size: 1.1rem;
  font-weight: 800;
}

.version-tag,
.eyebrow,
.section-label,
.next-step-label {
  color: var(--ink-soft);
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

.version-tag {
  padding: 6px 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
}

.section-label {
  margin: 0 0 14px;
  color: var(--cyan);
}

h1,
h2,
p {
  margin-top: 0;
}

.calculator-card,
.spec-panel {
  border: 1px solid var(--line);
  border-radius: 24px;
  box-shadow: var(--shadow);
}

.calculator-card {
  padding: 24px;
  background: linear-gradient(150deg, rgba(27, 46, 73, 0.98), rgba(14, 27, 46, 0.98));
}

.calculator-header {
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 22px;
}

.calculator-header h2,
.calculator-header h1,
.spec-panel h2 {
  margin: 0;
  font-size: 1.45rem;
  font-weight: 650;
  letter-spacing: -0.035em;
}

.status-chip {
  gap: 8px;
  color: var(--ink-soft);
  font-size: 0.75rem;
}

.status-dot {
  width: 8px;
  height: 8px;
  background: var(--cyan);
  border-radius: 50%;
  box-shadow: 0 0 0 5px rgba(110, 231, 212, 0.08);
}

.display {
  min-height: 166px;
  padding: 18px 20px 16px;
  background: #081321;
  border: 1px solid rgba(176, 201, 235, 0.12);
  border-radius: 18px;
}

.display-label,
.result-line {
  color: var(--ink-soft);
  font-size: 0.75rem;
}

.expression {
  min-height: 58px;
  overflow-wrap: anywhere;
  color: var(--ink);
  font-size: clamp(2rem, 5vw, 3rem);
  font-variant-numeric: tabular-nums;
  font-weight: 600;
  letter-spacing: -0.05em;
  line-height: 1.1;
  text-align: right;
}

.result-line {
  justify-content: space-between;
  gap: 16px;
  padding-top: 14px;
  border-top: 1px solid var(--line);
}

.result-line strong {
  color: var(--cyan);
  font-size: 1.1rem;
  font-weight: 600;
}

.result-value {
  display: flex;
  align-items: baseline;
  justify-content: flex-end;
  gap: 12px;
  min-width: 0;
  text-align: right;
}

.remainder {
  color: var(--ink-soft);
  font-size: 0.78rem;
  font-weight: 500;
  white-space: nowrap;
}

.division-note {
  flex-wrap: wrap;
  gap: 8px;
  padding: 14px 2px 18px;
  color: var(--ink-soft);
  font-size: 0.74rem;
}

.division-key {
  color: var(--blue);
  font-size: 1rem;
  font-weight: 700;
}

.keypad {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
}

.key {
  min-height: 60px;
  padding: 8px;
  color: var(--ink);
  background: rgba(234, 241, 255, 0.08);
  border: 1px solid rgba(176, 201, 235, 0.14);
  border-radius: 14px;
  cursor: pointer;
  font-size: 1.08rem;
  font-variant-numeric: tabular-nums;
  transition: transform 140ms ease, background 140ms ease, border-color 140ms ease;
}

.key:hover {
  background: rgba(234, 241, 255, 0.14);
  border-color: var(--line-strong);
}

.key:disabled,
.key:disabled:hover {
  color: rgba(170, 185, 212, 0.42);
  background: rgba(234, 241, 255, 0.03);
  border-color: rgba(176, 201, 235, 0.08);
  cursor: not-allowed;
  opacity: 0.7;
  transform: none;
}

.key:active {
  transform: translateY(2px) scale(0.98);
}

.key:focus-visible {
  outline: 3px solid rgba(110, 231, 212, 0.75);
  outline-offset: 2px;
}

.key-secondary {
  color: var(--ink-soft);
  background: transparent;
}

.key-operator {
  color: var(--blue);
  background: rgba(78, 143, 243, 0.13);
  border-color: rgba(139, 184, 255, 0.22);
}

.key-division {
  color: var(--cyan);
  background: rgba(110, 231, 212, 0.1);
  border-color: rgba(110, 231, 212, 0.2);
}

.key-zero {
  grid-column: span 3;
}

.key-equals {
  grid-column: 1 / -1;
  color: #07111f;
  background: var(--cyan);
  border-color: var(--cyan);
  font-size: 1.25rem;
  font-weight: 750;
}

.key-equals:hover {
  background: #8df4e4;
  border-color: #8df4e4;
}

.prototype-note {
  margin: 16px 2px 0;
  color: var(--ink-soft);
  font-size: 0.72rem;
  text-align: center;
}

.spec-panel {
  padding: 28px;
  background: rgba(15, 27, 46, 0.68);
}

.spec-panel h2 {
  margin-bottom: 14px;
}

.spec-copy {
  margin-bottom: 28px;
  color: var(--ink-soft);
  font-size: 0.88rem;
}

.scope-list {
  display: grid;
  gap: 20px;
}

.scope-item {
  align-items: flex-start;
  gap: 14px;
}

.scope-index {
  flex: 0 0 auto;
  color: var(--cyan);
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 0.76rem;
  font-weight: 700;
}

.scope-item strong {
  display: block;
  margin-bottom: 4px;
  font-size: 0.9rem;
  font-weight: 650;
}

.scope-item p {
  margin-bottom: 0;
  color: var(--ink-soft);
  font-size: 0.8rem;
}

.next-step {
  align-items: flex-start;
  gap: 14px;
  margin-top: 30px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
}

.next-step-label {
  flex: 0 0 auto;
  color: var(--blue);
}

.next-step p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 0.8rem;
}

@media (max-width: 460px) {
  .app-shell {
    width: min(100% - 24px, 1120px);
    padding-top: 18px;
  }

  .calculator-card,
  .spec-panel {
    padding: 18px;
    border-radius: 20px;
  }

  .keypad {
    gap: 8px;
  }

  .key {
    min-height: 54px;
    border-radius: 12px;
  }
}