.course_header {
    height: 45px;
} 
.course_header::after {
    content: ''; 
    display: block; 
    clear: both

}
.page_name { float: left;}
.sel_sort { 
    float: right;
    height: 35px;
    padding: 0 25px 0 10px;
    outline: none; 
    background-color: #fff;
    border: 1px solid #ddd;
}
select { -webkit-appearance: none; /* 네이티브 외형 감추기 */ -moz-appearance: none; appearance: none; background: url(../img/carrot.png) no-repeat 88% 53% / 10px /* 화살표 모양의 이미지 */ } /* IE 10, 11의 네이티브 화살표 숨기기 */ select::-ms-expand { display: none; }

/* 왼쪽 메뉴 */
.l_filter {
    width: 236px; 
    border: 1px solid #b5b5b5;
    padding: 0 20px;
    box-sizing: border-box;
    float: left;

    user-select: none;
}
.list_box_title {
    font-size: 18px;
    margin-bottom: 10px;
} 
/* 스마트용 기기에서 화살표 */
.carrot {
    display: none;
}
.lbl_chk {
    width: 17px;
    height: 17px;
    border: 1px solid #b5b5b5;
    /* background: red; */
    /* display: inline-block; */
    float: left;
    margin-top: 6px;
    margin-right: 10px;
}
.chk_mark {
    width: 5px;
    height: 10px;
    border-right: 3px solid #5f5f5f;
    border-bottom: 3px solid #5f5f5f;
    transform: rotate(35deg) translate(5px, -2px);
    display: none;
}
input[type="checkbox"]:checked + .lbl_chk > .chk_mark {
    display: block;
}
.l_filter input[type="checkbox"] {
    display: none;
}
.list_box {
    border-bottom: 1px solid #b5b5b5;
    padding: 30px 0;
}
.list_box:last-child {
    border: none;
}
.list_box li {
    height: 30px;
    line-height: 30px;
    font-size: 14px;
}
.list_box li label, .list_box li a {
    display: block;
    cursor: pointer;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
} 
.list_box li a::before {
    content: "- ";
}




/* 본문 메인 */
.contents_container {
    width: calc(100% - 236px);
    float: right; 
    margin-bottom: 20px;
}
.item_container {
    width: 100%;
    overflow: hidden;
    /* padding: 0 5px; */
    padding-left: 30px;
    box-sizing: border-box;
    /* margin-top: 10px;  */
}
/* .item_contents {
    display: block;
    width: calc((100% - (30px * 1)) / 2 - 0.01px); 
    margin-right: 30px;
    margin-bottom: 30px;
    background: #fff; 
    border: 1px solid #bdbdbd;
    box-sizing: border-box;
    float: left;
}
.item_contents:nth-child(2n) {
    margin-right: 0;
} 
.item_contents_img {
    width: 100%;
    height: 200px;
    background: gray;
}
.item_contents_desc {
    padding: 10px;
    box-sizing: border-box;
}*/
.content_title { 
    /* overflow:hidden;
    text-overflow:ellipsis;
    display:-webkit-box;
    -webkit-line-clamp:2; /* 라인수 */
    
    /* -webkit-box-orient:vertical;
    word-wrap:break-word;
    line-height:25px;
    height:50px;  
    color: #454545;
    font-size: 17px;   */
}
.content_title:hover {
    /* text-decoration: underline; */
}
.content_desc  {
    /* height: 20px;
    margin-top: 12px;
    font-size: 12px;
    color: #595959; */
}  
.level, .group {
    /* float: left; */
} 
.class_like {
    /* float: right;
    width: 20px;
    height: 20px;
    
    background: url(../img/heart_empty.png) no-repeat center / contain; */
    /* background: url(../img/heart.png) no-repeat center / contain; */
} 


/* 실제 컨텐츠들 */
.class_material {
    position: relative;
    width: calc(((100% - (10px)) / 2) - 0.1px);
    /* height: 392px; */

    overflow: hidden;;
    margin-right: 10px;
    margin-bottom: 10px;
    float: left;
    background: #fff;
    /* box-shadow: 1px 1px 5px 0 rgba(0,0,0,0.3); */
    border: 1px solid #b5b5b5;
    box-sizing: border-box;
    border-radius: 5px;
}
.class_material:nth-child(even)  {
    margin-right: 0;
}
.class_material:nth-child(3), .class_material:nth-child(4) {
    /*margin-bottom: 0;*/
}
.class_material > .sec_title{ 
    border-bottom: 2px solid #ff4848;
} 
.material_title {
    overflow: hidden;
    height: 40px;
    line-height: 40px;

    padding: 0 10px;
}
.material_title > h3 {
    float: left;
    font-size: 16px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    width: calc(100% - 50px);
    color: #2f2f2f;
}
.material_title > span {
    float: right;
    /* margin-bottom: 10px;
    font-size: 14px;
    position: relative;
    right: 0; 
    width: 11px;
    height: 100%; */
}
.material_title .show_more {
    width: 30px;
    height: 40px;
    display: block;
    position: relative;
    right: -10px;
}
.material_title .show_more:hover::before,
.material_title .show_more:hover::after {
    transform: translate(-50%, -50%) rotate(180deg);
    background: #222;
} 
.material_title .show_more::before,
.material_title .show_more::after {
    content: "";
    display: block;
    background: #656565;
    /* background: #222; */
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
    border-radius: 5px;
    transition: all 0.3s;
}
.material_title .show_more::before {
    width: 12px;
    height: 3px; 
    /* left: 0px;
    top: 18px; */
}
.material_title .show_more::after {
    width: 3px;
    height: 12px; 
    /* left: 4px;
    top: 14px; */
}
.material_contents {
    width: 100%;
    height: 251px;
}
.contents_row:nth-child(6) {
    border-bottom: none;
}
.material_contents > h2,
.item_container > h2 {
    text-align: center;
    color: red;
    /* margin-top: 150px; */
    line-height: 250px;
    font-size: 20px;
}
.contents_row {
    width: 100%;
    /* height: 40px; */
    line-height: 40px;
    padding: 0 10px;
    border-bottom: 1px solid #ddd;
    box-sizing: border-box;
    overflow: hidden;
    vertical-align: middle;
    display: inline-block;
}
.contents_row:hover {
    /* background-color: #deeeff;
    box-shadow: 0 8px 8px 0 rgba(0,0,0,0.3),
                0 0px 8px 0 rgba(0,0,0,0.1),
                0 6px 18px 0 rgba(0,0,0,0.1); 
    transition: all 0.2s; */
    cursor: pointer;

    cursor: pointer;
    background-color: #1596f9;
    color: #fff;
    box-shadow: none;
}
.contents_title {
    float: left;
    max-width: calc(100% - 80px);
    text-align: left;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}
.contents_title > span {
    margin-left: 5px;
    font-size: 14px;
}
.contents_upload_date {
    float: right;
    width: 80px;
    text-align: right;
    font-size: 13px;
}


@media screen and (max-width: 900px) {
    .l_filter {
        width: 215px;
        padding: 0 20px; 
    }
    .contents_container {
        width: calc(100% - 215px);
    }
    .item_container {
        padding-left: 10px;
    }
    .item_contents { 
        width: calc((100% - (2% * 1)) / 2 - 0.01px); 
        margin-right: 2%;
    }
    .item_contents:nth-child(2n) {
        margin-right: 0px;
    }
    .item_contents:nth-child(3n) {
        margin-right: 2%;
    }

    .contents_title { 
        max-width: 100%; 
    }
    .contents_upload_date {
        display: none;
    }
}

@media screen and (max-width: 600px) {
    .main_section {
        padding: 50px 10px 0px;
    }
    .l_filter {
        width: 100%;
        border: 1px solid #b5b5b5;
        padding: 0;
        box-sizing: border-box;
        float: left; 
    }
    .list_box {
        padding: 10px 10px;

        width: 100%;
        float: left;
        border-bottom: none;
        box-sizing: border-box;
    }
    .list_box:nth-child(2) {
        border-left: 1px solid #b5b5b5;
    }
    
    .list_box > ul {
        display: none;
    }
    .list_box_title {
        margin: 0;
        position: relative;
    }
    /* 스마트용 기기에서 화살표 */
    .carrot {
        display: block;
        position: absolute;
        right: 0;
        top: 50%;
        transform: translateY(-50%);
        width: 13px;
    }
    .carrot_active {
        transform: translateY(-50%) rotate(180deg);
    }
    .list_box > .list_box_ul_active {
        display: block;
        margin-top: 10px;
    }

    /* 본문 */
    .contents_container  {
        width: 100%;
        margin-top: 20px;
        /* margin-bottom: 20px; */
    }
    .item_container {
        padding-left: 0;
    }
    
    .item_contents_img {
        height: 150px;
    }
}

@media screen and (max-width: 480px) {
    .class_material {
        width: 100%;
        margin-right: 0;;
    }
    .material_contents {
        width: 100%;
        height: calc(41px * 5);
    }
}