body{
  display:flex;
  justify-content:center;
  align-items:center;
  height:100vh;
  background:#0f172a;
  font-family:Arial;
}

.calculator{
  background:#1e293b;
  padding:20px;
  border-radius:15px;
}

#display{
  width:100%;
  height:50px;
  margin-bottom:10px;
  font-size:20px;
  text-align:right;
  padding:10px;
}

.buttons{
  display:grid;
  grid-template-columns:repeat(4,70px);
  gap:10px;
}

button{
  height:50px;
  font-size:18px;
  border:none;
  border-radius:10px;
  background:#334155;
  color:white;
  cursor:pointer;
}

button:hover{
  background:#475569;
}

.zero{
  grid-column:span 2;
}
box-shadow: 0 0 20px rgba(0,0,0,0.5);