style.css

*{
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}

body{
    font-family: 'PT Serif',serif;
    font-weight: normal;
    font-size: 15px;
    background: url("./images/pic-1.jpg");

    height: 20px;
}

.box{
    text-align: center;

    margin: 10px auto ;
    margin-top: 50px;
    margin-bottom: 50px;
    
    color: #f5f5f5;

    height: 90vh;
    width: 50vh;

    border: 2px solid white;
    border-radius: 5px;
    outline: none;

    box-shadow: 3px 2px 11px 5px rgba(108, 109, 109, 0.91);
}

#counter{
    margin-top: 3rem;
    font-size: 40px;
}

#display{
    font-size: 200px;
    color: #008000;
}

button{
    font-size: 20px;
    font-family: 'PT Serif', serif;

    margin: 15px;

    padding: 15px 35px;
    border: 2px none;
    border-radius: 6px;
    
    color: #fff;
    background: #0d2c54;
    background-size: 200% auto;

    text-align: center;
    text-transform: uppercase;

    box-shadow: black 0 10px 10px -5px;
    transition: 0.5s;

    cursor: pointer;

}

.btn{
    margin-top: 20px;
}

.btn-grad {
    background-image: linear-gradient(to right, #0d2c54 0%, #0d2c54 51%, #232526 100%);

    margin-top: 10px;

}

.btn-grad:hover {
    background-position: right center;
    color: #fff;
    text-decoration: none;
}

.d-flex{
    display: flex;
}

.jc-center{
    justify-content: center;
}

/* MOBILE DESIGN */
@media (max-width: 500px) {
    body{
        height: 10px;
    }

    .box{
        text-align: center;
        margin-right: 50px;
        margin-left: 50px;

        height: 80vh;
        width: auto;
    }

    #counter{
        font-weight: 400px;
        font-size: 3em;
    }

    #display{
        font-size: 150px;
        margin-top: 8px;
    }
}