body{
    text-align: center;
}

.btn{
    height: 200px;
    width: 200px;
    border-radius: 20%;
    border: 10px solid black; 
    margin: 2.5rem;  
}

 .btn-container{
  display: flex;
  justify-content: center;
 }
 .red{
    background-color: red;
 }
 .blue{
    background-color: blue;
 }
 .green{
    background-color: green;
 }
 .yellow{
    background-color: yellow;
 }

 .flash{
   background-color: white;
 }
 .userFlash{
   background-color: lightblue;
 }