#learnbody {
    width: 100%;
    margin-top: 30px;
    margin-bottom: 30px;
    display: flex;
}

#catsection {
    width: 200px;
    min-width: 200px;
    min-height: 300px;
    margin-left: 10px;
    background-color: var(--thi-color);
    overflow: hidden;
}

#learnsection {
    position: relative;
    width: 100%;
    min-height: 700px;
    margin-right: 20px;
}

#cattitle {
    height: 35px;
    text-align: center;
    color: whitesmoke;
    font-size: 16px;
    font-weight: bold;
    background-color: #333333;
}

#cattitlea {
    position: relative;
    text-decoration: none;
    color: whitesmoke;
    top: 5px;
}

#catlist {
    color: whitesmoke;
    font-size: 15px;
    list-style-type: none;
}

    #catlist a {
        text-decoration: none;
    }

    #catlist li {
        margin-top: 3px;
    }

        #catlist a:hover {
            color: deepskyblue;
        }

.videosection {
    padding: 10px;
    width: 98%;
    background-color: var(--thi-color);
    margin-left: 1%;
    margin-bottom: 30px;
    overflow: hidden;
}

.videotitle {
    color: whitesmoke;
    font-size: 2vw;
    margin-left: 20px;
}

.videodesc {
    color: whitesmoke;
    font-size: 1.3vw;
    margin-left: 30px;
    font-weight: normal;
}

.learnvideo {
    max-width: 96%;
    height: auto;
    margin: 20px 2%;
}

.typetitle {
    color: gray;
    margin-left: -10px;
}

#catarea {
}

@media screen and (max-width: 900px) {
    #learnbody {
        display: inline-block;
    }

    #catsection {
        width: 80%;
        min-height: 200px;
        min-width: 0px;
        height: 200px;
        margin-left: 10%;
    }

    #catarea {
        height: 150px;
        overflow-y: auto;
    }

    #learnsection {
        position: relative;
        margin-right: 0px;
    }

    .videosection {
        padding: 0px;
        width: 94%;
        margin-left: 3%;
        margin-top: 30px;
        margin-bottom: 30px;
        overflow: hidden;
    }

    .learnvideo {
        width: 90%;
        height: auto;
        margin: 20px 5%;
    }

    .videotitle {
        font-size: 4vw;
        margin-left: 5%;
    }

    .videodesc {
        font-size: 3.2vw;
        margin-left: 7%;
    }
}