style.css

@import url('https://fonts.googleapis.com/css2?family=Orbitron&display=swap');

.title {
    font-family: 'Orbitron' , 'sans-serif';
    font-size: 50px;
    display: flex;
    justify-content: center;
    margin-top: 100px;
}
.calculator {
    padding: 10px;
    margin: auto;
    margin-top: 15vh;
    width: 400px;
    height: 380px;
    background-color: #191b28;
    border-radius: 10px;
}
.display-box {
    font-family: 'Orbitron' , 'sans-serif';
    background-color: white;
    color:#191b28;
    border-radius: 5px;
    width: 100%;
    height: 65%;
    border: solid black 0.5px;
}

#btn {
    background-color: #fb0066;    
}

.button {
    font-family: 'Orbitron' , 'sans-serif';
    background-color: #64278f;
    border: solid black 0.5px;
    color: white;
    width: 100%;
    height: 70%;
    border-radius: 5px;
    outline: none;

}
.button:active {
    background-color: #e5e5e5;
}