:root {
    --white-color: #fff;
    --black-color: #000;
    --header-height: 90px;
    --main-color: #235390;
    --main-color-plus-1: #0A4A82;
    --main-color-plus-2: #6D8DB6;
    --main-color-plus-3: #98B4D9;

    --text-primary: #000000;
    --text-secondary: #42637D;



    --main--text-color: #42637D;
    --separate-color: #cccccc;
    --grey-color: #ccc;
    --grey-plus-1-color: #E3E7EF;
    --main-introduce-color: #F6F6F6;
    --background-input-color: #F7F7F7;
    --background-bar-color: #E7EAF0;
    --shadow-input-color: #E5E5E5;
    --green-color: #58CC02;
    --green-shadow-color: #58A700;
    --height-input-login: 58px;
    --width-input-login: 450px;
    --btn-primary-color: #1CB0F6;
    --btn-primary-border-color: #5182C1;

    --background-card: #ffffff;
    --box-shadow-card: #E3E7EF;

    --size-responsive-mobile: 600px;
    --size-responsive-tablet: 900px;
    --size-responsive-laptop: 1200px;
    --size-responsive-laptop-large: 1536px;

    --answer-right-color: #D7FFB8;
    --answer-right-text-color: #8DBC00;
    --answer-false-color: #FFDFE0;
    --answer-false-text-color: #EC0B1B;
    --btn-danger-color: #FF4B4B;
    --btn-danger-border-color: #EC4444;


}

* {
    box-sizing: inherit;
    margin: 0;
    padding: 0;
}

a {
    text-decoration: none;
    color: inherit;
}

body,
html {
    font-family: 'Noto Sans', sans-serif;
}

html {
    font-size: 62.5%;

    box-sizing: border-box;
    color: var(--text-primary);
}

.btn {
    min-width: 130px;
    height: 50px;
    text-decoration: none;
    border-bottom: 5px solid var(--green-shadow-color);
    border-radius: 15px;
    font-size: 2rem;
    font-weight: 700;
    padding: 0 12px;
    outline: none;
    cursor: pointer;
    color: var(--white-color);
    display: inline-flex;
    justify-content: center;
    align-items: center;
    background-color: var(--green-color);
    -webkit-user-select: none;
    user-select: none;
    transition: all 0.1s linear;
}

.btn:hover:not(.btn--no_active) {
    filter: brightness(1.1);
}

.btn.btn--primary {
    background-color: var(--btn-primary-color);
    border-bottom: 5px solid var(--btn-primary-border-color);
}

.btn:active {
    border-bottom: 4px solid var(--green-shadow-color);

    transform: translateY(1px);
    opacity: 0.8;
}

.btn.btn--primary:active {
    border-bottom: 4px solid var(--btn-primary-border-color);
}

.btn.btn--card:active {
    border-bottom: 4px solid var(--box-shadow-card);
}

.btn.btn--no_active {
    cursor: auto;
}

.page__title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 32px;
}

p {
    margin: 0;
}

.disabled {
    pointer-events: none;
    opacity: 0.7;
}

.main_content-container {
    flex: 1;
    width: 100%;
}

.menu_right-container {
    width: 350px;
}

#study_content {
    flex-direction: column;
    display: flex;
    width: 100%;
    gap: 20px;
}

.study_review_button_container {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.study_review_button {
    min-width: 70px;
    width: 70px;
    height: 70px;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #D9D9D9;
    border-bottom: 7px solid #C6C6C6;
    border-radius: 10px;
    cursor: pointer;
    outline: none;
}

.study_review_button img {
    width: 100%;
    max-width: 30px;
    object-fit: cover;
}

.conjunction_container {
    display: flex;
    gap: 10px;
}

.conjunction_answer_container {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.character-answer.checked {
    border: 2px solid var(--btn-primary-color);
    background-color: #1cb0f66e;
}

#loading {
    display: flex;
    justify-content: center;
}

.study_container {
    margin-top: 18px;
    margin-bottom: 100px;
}

.study__footer_popup {
    padding: 10px;
    width: 100%;

    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
}

.study__footer_popup-container {
    max-width: 1100px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    gap: 10px;
    align-items: center;
    padding: 10px 0;
}

.study__footer_popup-container .icon {
    max-width: 50px;

}

.study__footer_popup-container .icon img {
    width: 100%;
    object-fit: cover;

}

.study__footer_popup-container .content {
    display: flex;
    flex-direction: column;
    gap: 10px;

}

.none-select {
    pointer-events: none;
    opacity: 0.7;
}

.background-wrong {
    background-color: #ffdfe0;
}

.background-right {
    background-color: #D7FFB8;
}

.background-exit {
    background-color: var(--white-color);

}

.answer__flase-img {
    max-width: 60px;
    width: 100%;
    object-fit: cover;
}

.btn.btn--danger {
    background-color: var(--btn-danger-color);
    border-bottom: 5px solid var(--btn-danger-border-color);
}

.answer__right-title {
    font-size: 3rem;
    font-weight: 700;

}

.answer__of-question {
    font-size: 1.8rem;
    font-weight: 500;
    margin-top: 4px;
    word-wrap: break-word;
    white-space: -moz-pre-wrap;
    white-space: pre-wrap;
    color: var(--grey-color);

}

.wrong {
    color: var(--answer-false-text-color);
}

.right {
    color: var(--answer-right-text-color);
}

.answer__container {
    display: flex;
    gap: 10px;
    align-items: center;
}

.check_exit {
    position: fixed;
    top: 0;
    bottom: 0;
    right: 0;
    left: 0;
    background-color: rgba(0, 0, 0, 0.4);
    display: flex;
}

.question__btn-stay.question__btn--no-active {
    background-color: var(--background-bar-color);
    border-bottom: 5px solid var(--background-bar-color);
}

.loading {
    display: none;
    position: fixed;
    top: 0;
    bottom: 0;
    right: 0;
    left: 0;
    justify-content: center;
    align-items: center;
    background-color: rgba(0, 0, 0, 0.4);
    z-index: 99;
}

.loading--open {
    display: flex;
}

.loading__wrap-img {
    background-color: var(--white-color);
    border-radius: 20px;
    display: flex;
    justify-content: center;
    align-items: center;
    width: 150px;
    height: 150px;
}

.loading__img {
    width: 130px;
    height: 130px;
}

a:hover {
    color: inherit;
}

textarea {
    resize: vertical;
}

.footer__container {
    display: flex;
    justify-content: space-between;
    color: var(--main-color-plus-2);

}

.why_use_container {
    grid-template-columns: repeat(4, minmax(0, 1fr));
    display: grid;
    gap: 20px;
}

.introduce_platform {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    display: grid;
    gap: 20px;
}



.card {
    box-shadow: 0 2px 0 var(--box-shadow-card);
    transition: all 0.25s linear;
}

.card:hover {}

::-webkit-scrollbar {
    width: 10px;
    height: 5px
}

::-webkit-scrollbar-thumb {
    background: #888;
    border-radius: 5px
}

::-webkit-scrollbar-track {
    background: inherit
}

input::placeholder {
    color: #BEB2B2;
}

*:focus {
    outline: none;
}

.tabcontrol-nav {
    display: flex;
    font-size: 2rem;
    color: var(--grey-color);
    font-weight: 700;
    border-bottom: 3px solid var(--grey-plus-1-color);
}

.tabcontrol-item {
    padding: 8px;
    margin-right: 14px;
    cursor: pointer;
    -webkit-user-select: none;
    user-select: none;
}

.tabcontrol-item.tab-active {
    color: var(--btn-primary-color);
    border-bottom: 3px solid var(--btn-primary-color);
    animation: Slide ease 0.3s;
}

button {
    border: none;
}

.introduce_website {
    padding: 10px;
    width: 100%;
    max-width: 1100px;
    margin: 0 auto;
    display: grid;
    gap: 10px;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    align-items: center;

}

.introduce_website-right {
    text-align: center;

}

.chatbot_content {
    min-height: 200px;
    max-height: 600px;
    width: 100%;
    overflow-y: auto;
}

.chatbot_form {
    gap: 10px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 0px;
    border-top: 3px solid var(--box-shadow-card);
}

.name-profile__file,
.name-login__file,
.name-email__file,
.input-text-profile {
    height: 60px;
    width: 100%;
    padding: 12px;
    background-color: var(--background-input-color);
    border: 3px solid #E5E5E5;
    border-radius: 15px;
    font-size: 1.8rem;
    font-weight: 400;
}

.chatbot_content {
    padding: 10px;
    overflow: auto;
}

.chatbot {
    display: flex;
    min-height: 120px;
    margin-bottom: 14px;
}

.chatbot.right {
    flex-direction: row-reverse;
}

.chatbot-avata {
    margin-right: 14px;
    align-self: flex-start;
    max-width: 40px;
    width: 100%;
    height: 40px;
    object-fit: cover;
    border-radius: 50%;
}

.chatbot-avata.right {
    margin-left: 14px;

}

.chatbot-content {

    border: 3px solid var(--grey-plus-1-color);
    border-radius: 20px;
    padding: 12px;
    display: flex;
    align-items: center;
}

.chatbot-content-wrap {
    flex: 1;
    height: 100%;
    font-size: 1.8rem;
    font-weight: 500;
    display: flex;
    flex-direction: column;
}

.chatbot-name {
    font-weight: 700;
    color: var(--main--text-color);
}

.chatbot-paragraph {
    color: var(--main--text-color);
    margin-top: 6px;
}

.chatbot-time {
    margin-top: auto;
    color: #928899;
}

.chatbot-content-text {
    font-size: 1.8rem;
    color: var(--text-secondary);
    font-weight: 500;
    text-align: center;
}

.chatbot_form_input-write {

    background-color: var(--background-input-color);
    border-radius: 15px;
    border: none;
    flex: 1;
    min-height: 55px;
    height: 55px;
    font-size: 1.8rem;
    font-weight: 400;
    color: var(--main--text-color);
    padding: 15px;
    overflow: hidden;
    border: 3px solid #E5E5E5;
}

.statistical {
    padding: 108px 20px 0px 0px;
}


button#clearButton {
    min-width: 130px;
    height: 50px;
    text-decoration: none;
    border-bottom: 5px solid #cc0b0b;
    border-radius: 15px;
    font-size: 2rem;
    font-weight: 700;
    padding: 0 12px;
    outline: none;
    cursor: pointer;
    color: var(--white-color);
    display: inline-flex;
    justify-content: center;
    align-items: center;
    background-color: var(--btn-danger-color);
    -webkit-user-select: none;
    user-select: none;
    transition: all 0.1s linear;
}

.img-face-back {
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}
.tab-buttons, .tab-content {
    display: none !important;
}

.dropdown-wrapper {
    width: 100%;
    margin-top: 20px;
}

.dropdown {
    position: relative;
    display: inline-block;
    width: 100%;
    margin-bottom: 10px;
    border: 1px solid var(--grey-plus-1-color);
    border-radius: 8px;
    overflow: hidden;
}

.dropbtn {
    background-color: #f0f0f0;
    color: var(--black-color);
    padding: 15px 20px;
    font-size: 1.6rem;
    font-weight: 700;
    border: none;
    cursor: pointer;
    width: 100%;
    text-align: left;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.dropbtn:hover, .dropbtn:focus {
    background-color: #e0e0e0;
}

.dropdown-content {
    display: none;
    background-color: #f9f9f9;
    min-width: 100%;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    z-index: 1;
    border-top: 1px solid var(--grey-plus-1-color);
}

.dropdown-chapter {
    position: relative;
    width: 100%;
}

.chapter-dropbtn {
    background-color: #ffffff;
    color: var(--black-color);
    padding: 12px 30px;
    font-size: 1.4rem;
    font-weight: 600;
    border: none;
    cursor: pointer;
    width: 100%;
    text-align: left;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-top: 1px solid #eee;
}

.chapter-dropbtn:hover, .chapter-dropbtn:focus {
    background-color: #f5f5f5;
}

.chapter-content {
    padding: 10px 20px 10px 50px;
    display: none;
    width: auto;
}

.arrow {
    font-size: 0.8em;
    transition: transform 0.3s ease;
}

.dropbtn.active .arrow {
    transform: rotate(180deg);
}

.chapter-dropbtn.active .arrow {
    transform: rotate(90deg);
}

.course-detail__content-container.grid {
    display: grid;
    gap: 20px;
    padding: 20px 20px;
}


.stage.card {
    border: 1px solid #ddd;
    border-radius: 8px;
    overflow: hidden;
    text-align: center;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    transition: transform 0.2s ease-in-out;
}

.stage.card:hover {
    transform: translateY(-5px);
}

.stage__index-background {
    position: absolute;
    top: 5px;
    left: 5px;
    background-color: rgba(0, 123, 255, 0.8);
    color: white;
    padding: 5px 10px;
    border-radius: 5px;
    font-size: 1rem;
    font-weight: bold;
}

.stage__learned {
    position: absolute;
    bottom: 5px;
    right: 5px;
    background-color: #28a745;
    border-radius: 50%;
    padding: 5px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.stage__learned--no-active {
    display: none;
}

.stage__learned-img {
    width: 20px;
    height: 20px;
    filter: invert(100%);
}

.stage__title {
    padding: 10px;
    font-size: 1.1rem;
    font-weight: 600;
    color: #333;
    min-height: 50px;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
}

.flex-column-custom{
    display: flex;
    flex-direction: column;
}