@import url('https://fonts.googleapis.com/css2?family=Orbitron&display=swap');
.calculator {
    padding: 10px;
    border-radius: 1em;
    height: 380px;
    width: 300px;
    margin: auto;
    background-color: #191b28;
    box-shadow: rgba(0, 0, 0, 0.19) 0px 10px 20px, rgba(0, 0, 0, 0.23) 0px 6px 6px;
}

.display-box {
    font-family:"Times New Roman", Times, serif;
    font-size: 2.5em; /* 40px/16=2.5em */
background-color: #dcdbe1;
    border: solid black 0.5px;
    color: #0000A0;
    border-radius: 5px;
    width: 100%;
    height: 65%;
}
#btn {
    background-color: #fb0066;
}
input[type=button] {
    font-family: Arial, Helvetica, sans-serif;
font-size: 2.5em; /* 40px/16=2.5em */    
background-color: #64278f;
    color: yellow;
    border: solid black 0.5px;
    width: 100%;
    border-radius: 5px;
    height: 70%;
    outline: none;
}
input:active[type=button] {
    background: #e5e5e5;
    -webkit-box-shadow: inset 0px 0px 5px #c1c1c1;
    -moz-box-shadow: inset 0px 0px 5px #c1c1c1;
    box-shadow: inset 0px 0px 5px #c1c1c1;