button{
    width: 100px;
    height: 100px;
    border-radius: 50px;
    border: none;
    background-color: hsl(0, 0%, 30%)
   

}

#keys{
    display: grid;
    grid-template-columns: repeat(4,1fr);
    gap: 10px;
    padding: 25px;
}

#calculator{
    font-family:Arial, sans-serif ;
    background-color: black;
    border-radius: 15px;
    max-width: 500px;
    overflow: hidden;
}

#display{
    width: 100%;
    padding: 20px;
    font-size:5rem ;
    text-align: left;
    border: none;
      background-color:hsl(0, 0%, 30%)
}

body{
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height:100vh ;
    background-color:hsl(0, 0%, 95%)
}

button:hover{
    background-color:hsl(0, 0%, 40%)
}

button:active{
    background-color: (0, 0%, 50%)
}
.operator-btn{
    background-color: orange;
}
.operator-btn:hover{
    background-color: orange;
}
.operator-btn:active{
    background-color: orange;
}