:root {
    --header-background-color: #F2F2F2;
    --header-text-color: #BF2A37;
    --general-text-color: #333;
    --main-background-color: #F2F2F2;
    --main-sub-color: #F29B88;
    --footer-background-color: #0D0D0D;
    --footer-text-color: #BF1515;
    --main-part-padding: 1rem 17.5rem;
    --tablet-portrait-main-part-padding: 1rem 2rem;   
    --mobile-landscape-main-part-padding: 0.5rem 1.5rem;    
}

* {
    margin: 0;
    padding: 0;
    text-decoration: none;
    list-style-type: none;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

a {
    cursor: pointer;
}

body {
    font-family: "Prompt", sans-serif;
    background-color: var(--main-background-color);
    color: var(--general-text-color);
}

.container {
    display: flex;
    flex-direction: column;
    justify-content: center;
    justify-self: center;
    align-items: center;
    min-height: 100vh;
}

header {
    display: flex;
    align-items: center;
    background-color: var(--header-background-color);
    color: var(--header-text-color);
    padding: var(--main-part-padding);
    justify-content: center;
    justify-items: center;
    gap: 8.5rem;

    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
}

header a {
    display: flex;
    align-items: center;
}

header img {
    max-width: 3.5rem;
    height: auto;
}

header .nav-button-or-menu-bar {
    position: relative;
    display: flex;
    align-items: center;
    justify-content: right;
}

header .nav-button {
    display: flex;
    align-items: center;
    gap: 4rem;
}

header ul {
    display: flex;
    gap: 2rem;
}

header li a {
    color: var(--general-text-color);
    text-align: center;
    font-size: 1rem;
    font-weight: 500;
}

header a:hover {
    color: var(--header-text-color);
}

header .header-button {
    display: flex;
    gap: 1rem;
}

.header-button a {
    padding: 0.5rem 1.5rem;
    background-color: var(--header-text-color);
    color: var(--header-background-color);
    border-radius: 1.5rem;
    border: none;
    font-size: 0.95rem;
    text-align: center;
    font-weight: 500;
    min-width: 12.5rem;
    cursor: pointer;
}

.header-button a:hover {
    color: var(--header-background-color);
}

header span {
    padding: 0.7rem 0;
    cursor: pointer;
    display: none;
}

.menu-bar-overlay {
    position: absolute;
    top: 0.35rem;
    right: 0.8rem;
    padding: 1.1rem 1.3rem;
    cursor: pointer;
    z-index: 10000;
}

header #nav-menu {
    display: none;
    position: absolute;
    top: 4.5rem;
    left: 0;
    border: var(--header-text-color) 0.05rem solid;
    border-left: none;
    border-right: none;
    border-bottom: none;
    width: 100%;
}

.banner-content {
    align-self: center;
}

.banner-content img {
    width: 100%;
    height: auto;
    margin-top: 5rem;
}

/* Code image slider */
.slider {
    width: 1518px;
    max-width: 100vw; 
    height: 37rem;
    margin: 5.48rem 0 3rem;
    position: relative;
    overflow: hidden;
}

.list {
    position: absolute;
    top: 0;
    left: 0;
    height: 100%;
    display: flex;
    width: max-content;
    transition: 1s ease-in-out;
}

.list img {
    width: 1518px;
    max-width: 100vw;
    object-fit: cover;
    height: 100%;
}

.buttons {
    position: absolute;
    top: 50%;
    left: 1%;
    width: 97.75%;
    display: flex;
    justify-content: space-between;
}

.buttons button {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    cursor: pointer;
    border: none;
    color: var(--general-text-color);
    background-color: var(--header-background-color);
}

.dots {
    position: absolute;
    top: 90%; 
    left: 0;
    width: 100%;
    height: fit-content;
    cursor: pointer;
    display: flex;
    justify-content: center;
}

.dots li {
    list-style: none;
    width: 10px;
    height: 10px;
    background-color: var(--header-background-color);
    margin: 10px;
    border-radius: 20px;
    transition: 1s ease-in-out;
}

.dots li.active {
    width: 30px;
}

main {
    padding: var(--main-part-padding);
    background-color: var(--main-background-color);
    align-items: center;
    justify-content: center;
    display: flex;
    flex-direction: column;
    gap: 8rem;
    width: 100%;
}

/* Code phần giới thiệu */
#about {
    display: flex;
    padding: var(--main-part-padding);
    max-width: 100%;
    align-items: center;
    justify-content: center;
    margin-top: 4rem;
    padding: 1rem 0;
    gap: 1rem;
    scroll-margin-top: 10rem;
}

.about-text {
    display: flex;
    flex-direction: column;
    align-self: center;
    gap: 1rem;
}

.about-text h1 {
    font-size: 2rem;
    color: var(--header-text-color);
}

.about-text p {
    font-size: 1.1rem;
    color: var(--general-text-color);
    margin-bottom: 1.5rem;
    max-width: 90%;
}

.about-text a {
    color: var(--footer-text-color);
    font-weight: 600;
    border: var(--header-text-color) 0.1rem solid;
    max-width: 9rem;

    display: flex;
    align-items: center;
    gap: 0.5rem;
    justify-content: center;
    padding: 0.5rem 0.8rem;
    border-radius: 1rem;
}

.about-image {
    max-width: 29.5rem;
    display: flex;
    align-items: center;
}

.about-image img {
    width: 100%;
    height: 100%;
    border-radius: 0.5rem;
    border: 0.15rem solid var(--main-sub-color);
}

iframe {
    height: 487px;
}

/* Code phần member */
#members {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    scroll-margin-top: 8rem;
    max-width: 100%;
}

#members h1 {
    font-size: 2.5rem;
    color: var(--header-text-color);
}

#members p {
    margin-bottom: 2.5rem;
    font-size: 1.1rem;
}

.members {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1rem;
    justify-content: center;
}

.members a {
    display: flex;
    align-items: center;
    /* max-width: 19.3rem; */
}

.members img {
    width: 100%;
    border-radius: 2rem;
    transition: all 0.4s ease-in-out;
}

.members img:hover {
    transform: scale(1.02);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

/* Code phần hoạt động */
#activities {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    max-width: 100%;    
    margin-bottom: 6rem;
    gap: 3rem;
    scroll-margin-top: 9.2rem;
}

.activities-title-content {
    display: flex;
    align-items: center;
    width: 100%;
    justify-content: space-between;
    /* gap: 36.2rem; */
}

.activities-title-content h1 {
    font-size: 2.5rem;
    color: var(--footer-text-color);
}

.activities-title-content a {
    color: var(--footer-text-color);
    font-weight: 600;
    border: var(--header-text-color) 0.1rem solid;

    display: flex;
    align-items: center;
    gap: 0.5rem;
    justify-content: center;
    padding: 0.5rem 0.8rem;
    border-radius: 1rem;
}

.activities {
    display: grid;
    grid-template-columns: repeat(3, minmax(15rem, 1fr));
    gap: 1rem;
    width: 100%;
    margin: 0;
    padding: 0;
}

.hoatdong {
    position: relative;
    display: flex;
    align-items: center;
    width: 100%;
    height: auto;
}

.activities img {
    width: 100%;
    height: auto;
    border-radius: 0.5rem;
    object-fit: cover;
}

.activities .hoatdong:first-child {
    width: 100%;
    grid-row: span 2;
    grid-column: span 2;
}

.noidung-hoatdong {
    display: flex;
    align-items: center;
    text-align: center;
    color: var(--main-background-color);
    position: absolute;
    width: 100%;
    height: 100%;
    font-size: 1.35rem;
    font-weight: 500;
    cursor: pointer;
    opacity: 0;
    justify-content: center;
    border-radius: 0.5rem;
    background-color: rgba(0, 0, 0, 0.55);
    transition: opacity 0.4s ease-in-out;
}

.hoatdong:hover .noidung-hoatdong {
    opacity: 1;
}

.overlay-to-activity-page {
    position: absolute;
    align-self: center;
    cursor: pointer;
    z-index: 10;
    width: 100%;
    height: 100%;
}

/* Code footer */
footer {
    display: flex;
    align-items: center;
    width: 100%;
    padding: 3rem 17.5rem;
    background-color: var(--footer-background-color);
    color: var(--footer-text-color);
    justify-content: center;
    gap: 7rem;
}

footer #footer-info {
    display: flex;
    flex-direction: column;
    gap: 3rem;
}

footer #info {
    display: flex;
    align-items: baseline;
    gap: 3rem;
}

footer img {
    max-width: 12rem;
    height: auto;
}

footer a {
    color: var(--footer-text-color);
}

.social-media {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.sc-md-link {
    display: flex;
    align-items: center;
    gap: 1rem;
}

@media screen and (max-width: 1450px) {
    .slider {
        height: 33.5rem;
    }

    .buttons {
        width: 96.75%;
    }

    footer {
        display: flex;
        align-items: center;
        width: 100%;
        padding: 3rem 17.5rem;
        background-color: var(--footer-background-color);
        color: var(--footer-text-color);
        justify-content: center;
        gap: 6rem;
    }
    
    footer #footer-info {
        display: flex;
        flex-direction: column;
        gap: 3rem;
    }
    
    footer #info {
        display: flex;
        align-items: baseline;
        gap: 2rem;
    }
    
    footer img {
        max-width: 11rem;
        height: auto;
    }

    #info h3, .copyright {
        font-size: 1rem;
    }

    #contact-title {
        margin-bottom: 0.25rem;
    }

    #info p, #info a {
        font-size: 0.9rem;
    }
}

/* Tablet Landscape */
@media screen and (max-width: 1240px) {
    header {
        gap: 2rem;
        align-items: center;
        justify-content: space-between;
        width: 100%;
        padding: var(--tablet-portrait-main-part-padding);
    }

    header img {
        max-width: 2.5rem; 
    }

    .banner-content img {
        margin-top: 3.4rem;
    }

    header .nav-button {
        display: none;
    }
    
    header ul {
        flex-direction: column; /* Chuyển các menu ngang thành dọc */
        gap: 1rem; /* Giảm khoảng cách giữa các mục menu */
    }
    
    header #nav-menu.show {
        display: flex;
    }

    #nav-menu ul {
        gap: 0;
        min-width: 100%;
    }

    #nav-menu ul li {
        padding: 0.3rem 2rem;
        width: 100%;
        background-color: var(--header-background-color);
        border: var(--header-text-color) 0.05rem solid;
        border-left: none;
        border-right: none;
        border-top: none;
        transition: all 0.2s ease-in-out;
    }

    #nav-menu ul li a {
        transition: all 0.2s ease-in-out;
    }

    #nav-menu ul li:hover {
        background-color: var(--main-sub-color);
    }

    #nav-menu ul li a:hover {
        color: var(--general-text-color);
        font-size: 1.15rem;
    }

    header span {
        display: flex;
    }

    .banner-content{
        max-width: 100%;
    }

    .slider {
        max-width: 100vw; 
        height: 30.5rem;
        margin: 4.4rem 0 1.6rem;
    }

    /* Code phần giới thiệu */
    main {
        padding: var(--tablet-portrait-main-part-padding);
        justify-self: center;
        gap: 5rem;
    }

    #about {
        align-items: baseline;
        align-self: center;
        gap: 2rem;
        margin-top: 4rem;
        padding: 1rem 0;
        scroll-margin-top: 4rem;
        max-width: 100%;
    }

    .about-text {
        display: flex;
        flex-direction: column;
        position: relative;
        width: 100%;
        gap: 1rem;
    }

    .about-text h1 {
        font-size: 1.8rem;
        color: var(--header-text-color);
    }

    .about-text p {
        font-size: 1rem;
        color: var(--general-text-color);
    }

    .about-text a {
        font-size: 0.9em;
        max-width: 9rem;
        gap: 0.5rem;
        padding: 0.3rem 0.5rem;
    }

    .about-image {
        max-width: 100%;
    }

    .about-image img {
        width: 100%;
    }

    /* Code phần member */
    #members {
        align-self: center;
        scroll-margin-top: 4rem;
    }

    #members h1 {
        font-size: 1.8rem;
    }

    #members p {
        font-size: 1rem;
    }

    .members {
        display: grid;
        grid-template-columns: repeat(2, 1fr);
        width: 100%;
    }

    .members img {
        width: 100%;
    }

    /* Code phần hoạt động */
    #activities {
        margin-bottom: 4rem;
        scroll-margin-top: 5rem;
    }

    .activities {
        grid-template-columns: repeat(2, 1fr);
    }

    .activities-title-content h1 {
        font-size: 1.8rem;
        
    }
    
    .activities-title-content a {
    
        padding: 0.3rem 0.5rem;
    }

    /* Code footer */
    footer {
        display: flex;
        align-items: center;
        justify-content: space-between;
        padding: 2.5rem 2rem;
        justify-content: baseline;
    }

    footer #footer-info {
        display: flex;
        gap: 3rem;
    }

    footer #info {
        display: flex;
        align-items: baseline;
        gap: 6rem;
    }

    #info h3, .copyright {
        font-size: 1.2rem;
    }

    #info p, #info a {
        font-size: 0.9rem;
    }

    footer img {
        max-width: 16rem;
        align-self: baseline;
    }
}

@media screen and (max-width: 1024px) {
    .slider {
        max-width: 100vw; 
        height: 26.5rem;
        margin: 4.4rem 0 1.6rem;
    }

    /* Code footer */
    footer {
        display: flex;
        align-items: center;
        justify-content: space-between;
        padding: 2.5rem 2rem;
        justify-content: baseline;
    }

    footer #footer-info {
        display: flex;
        flex-direction: column;
        gap: 3rem;
    }

    footer #info {
        display: flex;
        flex-direction: column;
        align-items: baseline;
        gap: 3rem;
    }

    footer img {
        max-width: 15rem;
        align-self: baseline;
    }
}

/* Mobile Landscape */
@media screen and (max-width: 760px) {
    header {
        gap: 1rem;
        padding: var(--mobile-landscape-main-part-padding);
    }

    header img {
        max-width: 2rem;
    }

    header .nav-button {
        display: none;
    }

    .banner-content img {
        margin-top: 3rem;
    }

    header ul {
        flex-direction: column;
        gap: 1rem;
    }

    header #nav-menu.show {
        top: 2.9rem;
    }

    #nav-menu ul li {
        padding: 0.3rem 1.5rem;
    }

    #nav-menu ul li a {
        font-size: 0.8rem;
    }

    #nav-menu ul li a:hover {
        font-size: 0.9rem;
    }

    .slider {
        max-width: 100vw; 
        height: 16.5rem;
        margin: 3rem 0 1.2rem;
    }

    .buttons {
        top: 45%;
        left: 2%;
        width: 95.75%;
    }

    .buttons button {
        width: 35px;
        height: 35px;
    }

    .dots {
        top: 85%;
    }

    .dots li {
        width: 5px;
        height: 5px;
        margin: 5px;
    }

    .dots li.active {
        width: 15px;
    }

    /* Code phần giới thiệu */
    main {
        padding: var(--mobile-landscape-main-part-padding);
    }

    #about {
        align-items: center;
        align-self: center;
        gap: 2.5rem;
        margin-top: 4rem;
        padding: 1rem 0;
        position: relative;
        flex-direction: column;
        
    }

    .about-text {
        display: flex;
        flex-direction: column;
        gap: 0.5rem;
        width: 100%;
    }

    .about-text h1 {
        font-size: 2.5rem;
    }

    .about-text p {
        font-size: 1.2rem;
        margin-bottom: 1rem;
    }

    .about-text a {
        position: static;
        align-self: flex-start;
        font-size: unset;
    }

    .about-image {
        max-width: none;
    }

    .about-image img {
        width: 100%;
        height: auto;
    }

    iframe {
        height: 343px;
    }

    /* Code phần member */
    #members {
        align-self: center;
    }

    #members h1 {
        font-size: 2.5rem;
        color: var(--header-text-color);
    }

    #members p {
        margin-bottom: 2.5rem;
        font-size: 1.2rem;
    }

    .members {
        display: grid;
        grid-template-columns: repeat(1, 1fr);
    }

    .members img {
        width: 100%;
    }

    /* Code phần hoạt động */
    .activities {
        grid-template-columns: repeat(1, 1fr);
    }

    .activities-title-content h1 {
        font-size: 2.5rem;
    }
    
    .activities-title-content a {
        padding: 0.3rem 0.5rem;
    }

    .activities .hoatdong:first-child {
        width: 100%;
        grid-row: 1;
        grid-column: 1;
    }

    /* Code footer */
    footer {
        display: flex;
        align-items: center;
        padding: 2.5rem 1.5rem;
        gap: 2.5rem
    }

    footer #footer-info {
        display: flex;
        flex-direction: column;
        gap: 3rem;
    }

    footer #info {
        display: flex;
        flex-direction: column;
        align-items: baseline;
        gap: 3rem;
    }

    #info h3 {
        font-size: 0.9rem;
    }

    #info p, #info a, .copyright {
        font-size: 0.7rem;
    }

    footer img {
        width: 10rem;
    }
}

@media screen and (max-width: 480px) {
    .slider {
        max-width: 100vw; 
        height: 10.5rem;
        margin: 3rem 0 0;
    }

    .buttons {
        top: 40%;
    }

    .about-text h1 {
        font-size: 1.25rem;
    }

    .about-text p {
        font-size: 0.9rem;
    }

    #members h1 {
        font-size: 1.5rem;
    }

    #members p {
        font-size: 0.9rem;
    }

    .activities-title-content h1 {
        font-size: 1.5rem;
    }

    .activities-title-content a {
        font-size: 0.8rem;
    }

    iframe {
        height: 187px;
    }

    footer {
        display: flex;
        align-items: center;
        padding: 2.5rem 1.5rem;
        gap: 2.25rem
    }

    #info h3 {
        font-size: 0.8rem;
    }

    #info p, #info a, .copyright {
        font-size: 0.6rem;
    }

    footer img {
        width: 6rem;
    }
}