.calc-shell {
  max-width: 420px;
  margin: 0 auto;
  display: grid;
  gap: 16px;
}

.calc-display {
  background: #0f172a;
  color: #e2e8f0;
  border-radius: 16px;
  padding: 16px 18px;
  display: grid;
  gap: 8px;
  box-shadow: inset 0 0 0 1px rgba(148, 163, 184, 0.2);
}

.calc-history {
  font-size: 13px;
  color: #94a3b8;
  text-align: right;
  min-height: 18px;
}

#calc-input {
  width: 100%;
  background: transparent;
  border: none;
  outline: none;
  color: #f8fafc;
  font-size: 28px;
  text-align: right;
}

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

.calc-btn {
  border: 1px solid rgba(15, 23, 42, 0.08);
  background: #f8fafc;
  color: #0f172a;
  border-radius: 14px;
  padding: 14px 0;
  font-size: 18px;
  font-weight: 600;
  transition: transform 0.08s ease, box-shadow 0.08s ease;
}

.calc-btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 16px rgba(15, 23, 42, 0.12);
}

.calc-btn:active {
  transform: translateY(0);
  box-shadow: none;
}

.calc-btn-op {
  background: #e0f2fe;
  color: #0369a1;
}

.calc-btn-alt {
  background: #fef3c7;
  color: #92400e;
}

.calc-btn-primary {
  background: #0f766e;
  color: #ffffff;
  border-color: transparent;
}

@media (max-width: 700px) {
  .calc-shell {
    max-width: 100%;
  }
}