* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Georgia', serif;
}

body {
    background: #ffffff;
    color: #333333;
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

nav {
    background: #002147;
    padding: 0.8rem 0;
    position: sticky;
    top: 0;
    border-bottom: 2px solid #b3a369;
    z-index: 1000;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.hamburger {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: 1rem;
    margin-left: auto;
    position: relative;
    width: 40px;
    height: 40px;
    transition: all 0.3s ease;
}

.hamburger::before,
.hamburger::after {
    content: '';
    position: absolute;
    left: 7px;
    right: 7px;
    height: 2px;
    background: white;
    transition: all 0.3s ease;
}

.hamburger::before {
    top: 12px;
    box-shadow: 0 8px 0 white;
}

.hamburger::after {
    bottom: 12px;
}

.hamburger.active::before {
    transform: rotate(45deg);
    top: 19px;
    box-shadow: none;
}

.hamburger.active::after {
    transform: rotate(-45deg);
    bottom: 19px;
}

nav ul {
    list-style-type: none;
    display: flex;
    justify-content: center;
    gap: 1.5rem;
    margin: 0;
    padding: 0;
    position: relative;
}

nav ul.active {
    max-height: 1000px;
    transition: all 0.5s ease;
}

nav a {
    color: #ffffff;
    text-decoration: none;
    font-size: 1.1rem;
    padding: 0.8rem 1.2rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    transition: all 0.3s ease;
    font-weight: 500;
    position: relative;
}

nav a::after {
    content: '';
    position: absolute;
    width: 0;
    height: 2px;
    bottom: 0;
    left: 0;
    background-color: #b3a369;
    transition: width 0.3s ease;
}

nav a:hover::after {
    width: 100%;
}

.has-submenu:hover .sub-menu {
    display: block;
    animation: fadeIn 0.3s ease;
}

.sub-menu {
    display: none;
    position: absolute;
    background: #002147;
    min-width: 220px;
    box-shadow: 0 8px 30px rgba(0,0,0,0.2);
    z-index: 1000;
}

.sub-menu li {
    padding: 0;
}

.sub-menu a {
    padding: 12px 20px;
    text-transform: none;
    border-bottom: 1px solid rgba(255,255,255,0.1);
    display: block;
    font-weight: 400;
}

.sub-menu a:hover {
    background: rgba(179, 163, 105, 0.1);
}

.header-container {
    background: linear-gradient(rgba(255,255,255,0.65), rgba(255,255,255,0.7)),
                url('../img/main.jpg');
    background-size: cover;
    background-position: center 65%;
    padding: 8rem 15%;
    text-align: center;
    flex: 1;
}

.conference-title {
    font-size: clamp(1.8rem, 4vw, 2.8rem);
    max-width: 1400px;
    margin: 0 auto;
    color: #002147;
    text-shadow: 1px 1px 2px rgba(0,0,0,0.1);
    line-height: 1.3;
}

.location-date {
    background: #b3a369;
    color: #002147;
    padding: 1rem 2rem;
    display: inline-block;
    margin: 2.5rem auto;
    font-weight: bold;
    letter-spacing: 1px;
    border-radius: 4px;
    font-size: clamp(0.9rem, 2vw, 1.1rem);
}

.content-section {
    padding: 4rem 15%;
    max-width: 1600px;
    margin: 0 auto;
}

.section-title {
    color: #002147;
    font-size: clamp(1.5rem, 2.5vw, 2.2rem);
    border-bottom: 2px solid #b3a369;
    padding-bottom: 0.5rem;
    margin-bottom: 2rem;
}

.welcome-message {
    max-width: 1200px;
    margin: 2rem auto;
    font-size: 1.1rem;
    line-height: 1.8;
    color: #444;
}

.highlight-box {
    background: #f8f9fa;
    border-left: 4px solid #b3a369;
    padding: 2rem 1.5rem;
    margin: 2.5rem 0;
    border-radius: 4px;
}

.highlight-box ul {
    padding-left: 2rem;
    columns: 2;
    gap: 2rem;
}

footer {
    background: #002147;
    color: white;
    padding: 2.5rem 0;
    border-top: 4px solid #b3a369;
    margin-top: auto;
    width: 100%;
}

.copyright {
    text-align: center;
    max-width: 1600px;
    margin: 0 auto;
    padding: 0 15%;
}

.copyright p {
    margin: 0;
    font-size: 0.95rem;
    color: rgba(255,255,255,0.9);
    line-height: 1.5;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.supporting-orgs {
    padding: 3rem 5%;
    margin: 3rem auto;
    max-width: 1400px;
}

.org-title {
    font-size: clamp(1.3rem, 2vw, 1.8rem);
    text-align: center;
    margin-bottom: 2rem;
    color: #002147;
}

.orgs-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 2.5rem;
    justify-content: center;
    align-items: center;
    padding: 0 1rem;
}

.org-logo {
    max-width: 200px;
    height: auto;
    margin: 0 auto;
    opacity: 0.9;
    transition: all 0.3s ease;
    display: block;
    width: 100%;
}

.polyu-logo {
    max-width: 280px;
}

.org-logo:hover {
    opacity: 1;
    transform: scale(1.05);
}

@media (min-width: 769px) and (max-width: 992px) {
    nav ul {
        gap: 0.5rem;
        padding: 0 2%;
    }
    
    nav a {
        font-size: 1rem;
        padding: 0.6rem 0.8rem;
        letter-spacing: 0.5px;
    }
    
    .has-submenu .sub-menu {
        min-width: 200px;
    }
    
    .sub-menu a {
        padding: 10px 15px;
        font-size: 0.95rem;
    }
    
    .header-container {
        padding: 6rem 8%;
    }
    
    .conference-title {
        font-size: 2.2rem;
    }
    
    .location-date {
        margin: 2rem auto;
        padding: 1rem 1.8rem;
    }
}

@media (max-width: 1200px) {
    .content-section {
        padding: 4rem 5%;
    }

    .highlight-box ul {
        columns: 1;
    }

    .orgs-grid {
        gap: 2rem;
    }
}

@media (max-width: 992px) {
    nav ul {
        flex-wrap: wrap;
        gap: 0.1rem;
        padding: 0 2%;
    }

    nav a {
        font-size: 1rem;
        padding: 0.6rem 0.7rem;
    }

    .header-container {
        padding: 6rem 5%;
    }
}

@media (max-width: 768px) {
    .hamburger {
        display: block;
    }
    
    nav ul {
        display: none;
        flex-direction: column;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: #002147;
        padding: 0;
        margin: 0;
        overflow: visible;
        align-items: center; /* Added for centering */
    }

    nav ul li {
        width: 100%; /* Full width for centering content */
        text-align: center; /* Center text alignment */
    }

    nav ul.active {
        display: flex; /* Show menu when active */
        opacity: 1;
        transform: translateY(0);
    }

    .hamburger {
        transition: transform 0.3s ease;
    }

    .hamburger.active {
        transform: rotate(180deg);
    }
    
    .has-submenu .sub-menu {
        display: none;
        position: static;
        background: rgba(0, 33, 71, 0.95);
        box-shadow: none;
        animation: none;
        width: 100%;
        padding-left: 0; /* Remove indentation */
    }
    
    .has-submenu.submenu-active .sub-menu {
        display: block;
        padding-left: 1.5rem;
    }

    nav a {
        display: block;
        padding: 1rem;
        font-size: 1.1rem;
        justify-content: center; /* Center content horizontally */
    }

    .sub-menu {
        width: 100%; /* Ensure full width */
        padding: 0; /* Remove default padding */
    }

    .sub-menu a {
        padding: 0.8rem 1rem !important;
        text-align: center !important; /* Force center alignment */
        font-size: 0.95rem;
        border-bottom: none;
    }

    .sub-menu li {
        padding: 0;
    }

    .sub-menu li:last-child a {
        border-bottom: none;
    }

    .conference-title {
        font-size: 1.8rem;
    }

    .location-date {
        margin: 1.5rem auto;
        padding: 0.8rem 1.5rem;
    }

    .orgs-grid {
        grid-template-columns: 1fr;
    }

    .org-logo {
        max-width: 50%;
    }

    .polyu-logo {
        max-width: 60%;
    }
}

@media (max-width: 576px) {
    .header-container {
        padding: 4rem 5%;
    }

    .conference-title {
        font-size: 1.6rem;
    }

    .location-date {
        font-size: 0.9rem;
        padding: 0.7rem 1.2rem;
    }

    .org-logo {
        max-width: 220px;
    }

    .polyu-logo {
        max-width: 260px;
    }
}

@media (max-width: 400px) {
    .conference-title {
        font-size: 1.4rem;
    }

    .location-date {
        font-size: 0.8rem;
    }

    .org-logo {
        max-width: 200px;
    }

    .polyu-logo {
        max-width: 240px;
    }
}