.calc-shell {
  width: min(560px, 94vw);
}

.calc-frame {
  border: 1px solid var(--border);
  border-radius: 18px;
  padding: 1rem;
  background: linear-gradient(165deg, #ffffff 0%, #f8f4ed 100%);
  box-shadow: var(--shadow);
}

.calc-display {
  display: block;
  width: 100%;
  min-height: 78px;
  border-radius: 12px;
  border: 1px solid #d7cfc2;
  background: #ffffff;
  color: #1a120a;
  padding: 0.75rem 0.85rem;
  margin: 0 0 0.8rem;
  text-align: right;
  font-family: "IBM Plex Mono", monospace;
  font-size: clamp(1.6rem, 5.2vw, 2.2rem);
  overflow-x: auto;
}

.calc-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 0.5rem;
}

.key {
  border: 1px solid #d7cfc2;
  border-radius: 12px;
  background: #fff;
  color: #19130f;
  font: inherit;
  font-size: 1.05rem;
  font-weight: 600;
  padding: 0.72rem 0.25rem;
  cursor: pointer;
  transition: transform 120ms ease, border-color 120ms ease, background-color 120ms ease;
}

.key:hover,
.key:focus-visible {
  transform: translateY(-1px);
  border-color: var(--accent);
}

.key-fn {
  background: #f2ece2;
}

.key-op {
  background: #dcf3ec;
  border-color: #9bcfbe;
}

.key-eq {
  background: var(--accent);
  border-color: var(--accent);
  color: #ffffff;
  font-weight: 700;
}

.key-zero {
  grid-column: span 2;
}