Homework 5 CSS

Homework 5
html {
    background-color: aquamarine;
}
body {
    font-family: Arial;
    margin: 0 auto;
    padding: 0;
    max-width: 1080px;
}
h1 {
    font-size: 48px;
}
h2 {
    font-size: 36px;
}
h3 {
    font-size: 24px;
}
h1, h2, h3, p {
    margin-left: 20px;
}
p {
    line-height: 1.7;
}
.semester p {
    margin: 0;
    margin-bottom: 20px;
}


.main {
    border: 0%;
    width: 100%;
    padding: 0%;
    margin: 0%;
    display: flex;
    flex-direction: column;
    /* justify-content: space-between; */
    background-color: rgb(218, 249, 255); 
}
.main img {
    width: 95%;      
    height: auto;
    margin: 0 auto;
    margin-bottom: 20px;
    max-width: 100%;
}


.course {
    display: flex;
    /* justify-content: space-between; */
    /* flex-direction: column; */
    margin-bottom: 30px;
    margin-left: 10px;
}
.semester {
    width: 100%;
    padding: 10px;
    border: 0px solid #ffffff;
    background-color: rgb(218, 249, 255);
}
.subject {
    border: 1px solid #000000;
    padding: 10px 0;
    margin: 0;
}
.subjectname {
    margin-left: 10px;
    font-size: 15px;
}


@media screen and (min-width: 480px) {
    body {
        width: auto;
    }
    h1, h2, h3, p {
        width: 95%;
    }
}
@media screen and (min-width: 480px) and (max-width: 750px) {
    .course {
        flex-direction: column;
    }

    .semester {
        margin-bottom: 30px;
        width: 95%;
    }

    .subject {
        margin-left: 0;
    }
}