body{
   margin: 0;
   display: flex;
   justify-content: center;
   align-items: center;
   height: 100vh;
}
#calculator{
   font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
   background-color: aquamarine;
   border-radius: 15px;
   max-width: 500px;
   overflow: hidden;
}
#display{
   width: 100%;
   padding: 20px;
   font-size: 5rem;
   text-align: left;
   border: none;
   background-color: #6cbda280;
   color: aliceblue;
}
#keys {
   display: grid;
   grid-template-columns: repeat(4, 1fr);
   gap: 10px;
   padding: 25px;
}
button {
   width: 100px;
   height: 100px;
   border-radius: 10%;
   border: none;
   background-color: #0f53fd;
   color: aliceblue;
   font-size: 3rem;
   font-weight: bold;
   cursor: pointer;
}
button:hover {
   background-color: #0f53fd90;
}
button:active {
   background-color: #0f53fd50;
}
.operator-btn{
   background-color: #fd920f;
}
.operator-btn:hover {
   background-color: #fd920f90;
}
.operator-btn:active {
   background-color: #fd920f50;
}