body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background: #f3f3f3;
  margin: 0;
}

.calc {
  background: #222;
  border-radius: 16px;
  box-shadow: 0 4px 24px rgba(0, 0, 0, 0.2);
  padding: 24px;
  max-width: 340px;
  width: 100%;
}

.body-calc {
  display: grid;
  grid-template-columns: repeat(4, 1fr); /* Use 4 columns */
  gap: 12px;
}

.show {
  grid-column: 1 / -1;
  height: 48px;
  font-size: 1.5rem;
  margin-bottom: 12px;
  text-align: right;
  padding: 0 12px;
  border-radius: 8px;
  border: none;
  background: #fff;
  color: #222;
}

.btn,
.red-btn {
  height: 48px;
  font-size: 1.2rem;
  border-radius: 8px;
  border: none;
  background: #444;
  color: #fff;
  cursor: pointer;
  transition: background 0.2s;
}

.btn:active,
.red-btn:active {
  background: #666;
}

.red-btn {
  background: #e74c3c;
}

.red-btn:active {
  background: #c0392b;
}

.red-btn {
  grid-column: span 2;
}

/* Responsive styles */
@media (max-width: 480px) {
  .calc {
    max-width: 98vw;
    padding: 8px;
    border-radius: 8px;
  }
  .body-calc {
    grid-template-columns: repeat(4, 1fr); /* Use 4 columns on mobile too */
    gap: 6px;
  }
  .show {
    height: 36px;
    font-size: 1.1rem;
    padding: 0 6px;
    border-radius: 4px;
    margin-bottom: 6px;
  }
  .btn,
  .red-btn {
    height: 36px;
    font-size: 1rem;
    border-radius: 4px;
  }
}