style.css

@import url('https://fonts.googleapis.com/css2?family=Fira+Sans:wght@500&display=swap');
@import url('https://fonts.googleapis.com/css2?family=Ubuntu:wght@300;500&display=swap');

#container{
    width:80%;
    margin:auto;
    max-width: 1050px;
}
h3{
    font-family: 'Fira Sans', sans-serif;
    font-size: 40px;
    color: #ed553b;
    margin: 20px 0;
}
#calculator{
    display: grid;
    position: relative;
    grid-template-columns: repeat(5,1fr); /**/
    grid-gap: 10px; /**/
}
#calculator h3{
    grid-column: 1 / 3; /**/
}
#output-1{
    box-sizing: border-box;
    width: 100%;
    height: 70px;
    padding: 35px 0px 10px 7px;
    border-radius: 10px;
    border: solid 2px #20639b;
    margin-right: 100px;
    grid-column: 1/6;
    outline: none;
    font-family:  'Ubuntu', sans-serif;
    font-size: 29px;
    cursor: pointer;
}
#output-1:focus{ border: solid 3px #75b6eb;}
#output-2{
    box-sizing:border-box;
    position: absolute;
    padding: 0px 0px 10px -100px;
    top: 111px;
    left:5px;
    width:98%;
    height: 25px;
    border:none;
    border-bottom: 5px #20639b ;
    grid-column: 1/6; /**/
    outline: none; 
    font-family:  'Ubuntu', sans-serif;
    font-style: italic;
    font-size: 14px;
    color:rgb(172, 172, 172);
    cursor: pointer;
}
.button{
    width: 100%;
    height: 60px;
    border-radius: 10px;
    background-color: #f6d55c;
    border: none;
    outline: none;
    font-family:  'Ubuntu', sans-serif;
    font-size: 32px;
    color: #3caea3;
    cursor:pointer;
}
.button:hover{
    opacity: .7;
}
.button:focus{
    background-color:rgb(255, 38, 0);
    color:rgb(235, 235, 235);
}
.result{
    grid-column: 3 / 6; /**/
    background-color: #3caea3;
    color: #f6d55c;
}
.Addition , .division,
.multiplication , .subtraction{
    background-color: #3caea3;
    color: #f6d55c;
}
.trans{
    background-color: #359c92ab;
    color: #f6d55c;
}
._0 ,._1 ,._2 ,._3 ,._4 ,._5 ,._6 ,._7 ,._8 ,._9, ._dot{
    background-color: #e4e4e4;
    color: #ed553b;
}
@media (min-width: 900px){  
    #container{
        width:55%;
    }
    #calculator{
      grid-gap: 20px;
    }
}