.header {
    width: auto;
    height: 100%;
    display: inline-block;
    z-index: 1;
    float: left;
}
.header_list-mobile {
    list-style: none;
    padding: 0;
}
.header_list {
    list-style: none;
    font-size: 20px;
    padding-left: 10px;
}
.header_items .header-menu {
    display: none;
}
.header-menu {
    display: none;
    width: 40px;
}
.header_items {
    line-height: 40px; 
}
.header_items a {
    margin: 6px;
}
.header_items:hover {
    border-radius: 6px;
    background-color: #cccc;
}
.container {
    display: block;
    margin: 36px 0 0 60px;
    position: relative;
}
.container__GT {
    text-align: center;
    display: inline-block;
    margin: 0 28%;
    background-color: aliceblue;
    border-radius: 10px;
}
.header__container {
    font-size: 20px;
    margin: 12px 0 6px 0;
    
}
.content__container {
    margin: 0 10px 10px;
}
.container__list {
    display: block;
    font-size: 15px;
    
}
.container__learn {
    width: 100%;
    display: grid;
    margin-left: 82px;
}
.learn__content {
    display: inline-flex;
    margin-bottom: 30px;
}
.learn__heading {
    float: left;
    font-weight: 600;
    font-size: 30px;
    margin: 10px 0;
}
.learn__slide-1 {
    font-size: 20px;
    background-color: #3c55ed;
    color: white;
    display: inline-block;
    padding: 40px;
    margin: 5px 5px 5px 0;
    border-radius: 10px;
    cursor: pointer;
    max-width: 220px;
    max-height: 100px;
    text-align: center;
    line-height: 20px;
}
.learn__slide-1:hover {
    opacity: 0.9;
}
.container__note {
    margin: 31px 0;
}
.footer {
    background-color: #f5f5f5;
    padding: 14px 0;
    position: absolute;
    bottom: 0;
    right: 0;
    left: 0;
    margin: 0;
}
.footer span {
    font-size: 14px;
    display: flex;
    justify-content: center;
    line-height: 33px;
}
.container__note {
    margin-left: 115px;
}
.container h1 {
    font-size: 30px;
    text-align: center;
    margin: 10px 0;
}
.btn-next {
    float: right;
    font-size: 20px;
    font-weight: 600;
    background-color: #6900ff;
    padding: 5px;
    border-radius: 5px;
    color: white;
    margin: 10px 119px;
    cursor: pointer;
}
.btn-next:hover {
    opacity: 0.8;
}
.not-next {
    background-color: #757575;
}
.not-next:hover {
    opacity: 1;
    cursor: none;
}

/* bài tập */
.learn__ex {
    display: flex;
}
.bai-tap {
    font-size: 20px;
    background-color: #3c55ed;
    color: white;
    display: inline-block;
    padding: 20px;
    margin: 5px 5px 5px 0;
    border-radius: 10px;
    cursor: pointer;
    max-width: 220px;
    max-height: 65px;
    text-align: center;
    line-height: 20px;
}
.learn__ex:hover .noidung-baitap {
    /* display: block; */
    display: block;
    animation: fadeIn ease-in .4s;
}

.noidung-baitap {
    border: 1px solid #3700ff;
    color: white;
    background-color: #6900ff;
    /* max-width: 500px; */
    display: inline-block;
    font-size: 14px;
    padding: 5px;
    border-radius: 5px;
    margin: 0 12px;
    position: relative;
    display: none;
    width: 500px;
    height: 155px;
}
.noidung-baitap::after {
    content: "";
    border-width: 20px 26px;
    border-style: solid;
    border-color: transparent #6900ff transparent transparent;
    margin-left: -52px;
    float: left;
    margin-top: -132px;
   
}
.content_LT {
    margin: 0 20px 0 0;
    width: 30%;
    height: 800px;
    overflow: auto;
}
.content__HD {
    width: 70%;
}
.BT__tieu-de {
    left: 0;
    display: flex;
    font-size: 30px;
}
.BT__noi-dung {
    display: -webkit-box;
    font-size: 18px;
    margin: 5px 0;
}
.BT__noi-dung--TD {
    display: -webkit-box;
    font-size: 20px;
    font-weight: 600;
}
.BT__output {
    font-size: 14px;
    background-color: black;
    color: white;
    padding: 5px;
    border-radius: 4px;
    text-align: left;
    display: flex;
    overflow: auto;
    height: 100%;
}
.td-post-content table {
    margin-bottom: 21px;
}
table {
    width: 100%;
}
table th {
    text-align: left;
    border: 1px solid #ededed;
    padding: 2px 8px;
    font-size: 16px;
}
table td {
    border: 1px solid #ededed;
    padding: 2px 8px;
    font-size: 16px;
}
.BT__output-1 {
    margin: 10px 0px;
}