claculator.css

body{
	<background-image:src('bgimage.jpg');
}
.container{
    width: 300px;
    margin:0 auto;
    border: 1px solid black;
    box-sizing: border-box;
}

.row{
    display: flex;
    flex-direction: column;
    flex-wrap: wrap;
    justify-content: flex-start;
}
.display{
    padding: 10px;
    display: flex;
    flex-direction: column;

}
.display input{
    height: 50px;
    align-self: center;
    text-align: center;
    text-transform: uppercase;
    font-size:25px;
    border: none;
}

.input{
    width: 295px;
    display:flex;
    flex-direction: column;
    background-color: rgb(255, 255, 255);
    
}

.input div{
    display: flex;
    flex-direction: row;
    justify-content:center;
    box-sizing: border-box;

}
.input div button{
    padding: 15px;
    width: 70px;
    border: none;
    transition: all linear .5s;
    text-transform: uppercase;
    font-size: 20px;
    text-align: center;
    margin: 2px;

}
.input div button:last-child{
    background-color:rgb(6, 226, 241); 
}
.input div button:hover{
    background-color: aqua;
}