header {
    background-image: url('../images/rpf_header.PNG');
    background-repeat: no-repeat;
    background-size: 100% 100%;
}

iframe {
    display: block;
    margin: 1em auto; 
    border: 3px solid rgb(160, 159, 155);
}

.button_container {
    display: flex;
    justify-content: center;
    align-items: center;
    
}

.nav_buttons {
    font-size: 120%;
    padding: 10px 20px;
    margin: 1em 2em;
    cursor: pointer;
    border: 3px solid #080801;
    background-color: #e9ec06;
    width: 19%;
}

#back_button {
    border-top-right-radius: 40px;
    border-bottom-left-radius: 40px;
}

#next_button {
    border-top-left-radius: 40px;
    border-bottom-right-radius: 40px;
}

#current_page {
    font-size: 150%;
    font-weight: 600;
    color: #0a0a0a;
}

@media only screen and (max-width: 700px) {
    main {
        margin-right: 1em;
        margin-left: 1em;
    }
    iframe {
        width: 540px;
        height: 303px;
    }
    .nav_buttons {
        width: 27%;
    }
}

@media only screen and (max-width: 590px) {
    iframe {
        width: 440px;
        height: 247px;
    }
    #current_page {
        font-size: 120%;
        width: 20%;
    }
}

@media only screen and (max-width: 490px) {
    iframe {
        width: 340px;
        height: 191px;
    }
    .nav_buttons {
        margin: .5em;
        width: 30%;
    }
    #current_page {
        width: 23%;
    }
}

@media only screen and (max-width: 390px) {
    iframe {
        width: 280px;
        height: 157px;
    }
    .nav_buttons {
        width: 32%;
    }
    #current_page {
        font-size: 100%;
    }
}