.operator-btn{
  background-color:orange;
}
.operator-btn:hover{
  box-shadow: 0 0 20px orange;
}
body{
  display:flex;
  margin:0;
  justify-content:center;
  align-items:center;
  ;
  background-color:#e0e0e0
}
button:hover {
  box-shadow: 0 0 20px #00e5ff;
}
button{
  width:100px;
  height:100px;
  border-radius:50px;
  border:none;
  background-color:#00ffff;
  
  color:black;
  font-size:3rem;
  font-weight:bold;
  cursor:pointer;
  
}
#keys{
  display:grid;
  grid-template-columns:repeat(4,1fr);
  gap:10px;
  padding:25px;
  

}
#calculator{
  font-family:Arial,sans-serif;
  background-color:#0a0f1b;
  max-width:500px;
  overflow:hidden
 
}
#display{
  width:100%;
  padding: 20px;
  font-size:60px;
  background-color:#0a0f1b;
  text-align:left;
  border:none;
  color: #00ffff
}