body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background: rgb(13, 1, 54); /* dark background for contrast */
  font-family: Arial, sans-serif;
  padding: 40px;
}

.calculator {
  background: black;
  padding: 20px;
  border-radius: 12px;
  border: 1px solid white;
  display: flex;
  flex-direction: column; /* stack children vertically */
  width: max-content;     /* shrink to fit content */
  box-shadow: 0 0 10px rgba(255,255,255,0.1), 0 8px 20px rgba(0,0,0,0.6);
}

#display {
  width: 95%;
  height: 60px;
  font-size: 1.6rem;
  text-align: right;
  margin-bottom: 15px; /* space between display and buttons */
  padding: 10px;
  border: none;
  cursor: pointer;
  border-radius: 8px;
  background: #fdfcfc;
  color: black;
  box-shadow: inset 0 0 8px rgba(0,0,0,0.5);
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 70px);
  gap: 15px;
}

.btn {
  height: 60px;
  font-size: 1.2rem;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  background: #660000;
  color: #fff;
  transition: 0.2s;
}

.btn:hover {
  background: #800000;
}

.operator {
  background: #b22222;
}

.operator:hover {
  background: #a11d1d;
}

.clear {
  background: #990000;
}

.clear:hover {
  background: #cc0000;
}

/* Delete and Equal buttons share the row equally */
.delete, .equal {
  grid-column: span 2;   /* each takes half of the row */
  height: 60px;
}

/* Delete button styling */
.delete {
  background: #444;   /* neutral dark gray */
  color: #fff;
  border: 1px solid white;
}

.delete:hover {
  background: #666;
}

/* Equal button styling */
.equal {
  background: rgb(166, 120, 3);
  border: 1px solid white;
}

.equal:hover {
  background: gray;
}