/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f5f5;
}

/* Container */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
header {
    background-image: url('BG.jpg');
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    color: white;
    padding: 30px 20px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 100;
    transition: all 0.3s ease;
}

header .header-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, rgba(30, 58, 138, 0.85) 0%, rgba(59, 130, 246, 0.85) 100%);
    z-index: 1;
}

header .header-content {
    position: relative;
    z-index: 2;
    display: flex;
    align-items: center;
    gap: 30px;
}

header .logo {
    max-width: 150px;
    height: auto;
    background-color: white;
    padding: 15px;
    border-radius: 10px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.2);
    transition: all 0.3s ease;
    flex-shrink: 0;
}

.header-text {
    flex: 1;
    text-align: left;
}

header h1 {
    font-size: 2.5em;
    margin-bottom: 8px;
    font-weight: 700;
    letter-spacing: -1px;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
    transition: all 0.3s ease;
}

header .subtitle {
    font-size: 1.25em;
    margin-bottom: 5px;
    font-weight: 300;
    text-shadow: 1px 1px 3px rgba(0,0,0,0.3);
    transition: all 0.3s ease;
}

header .conference {
    font-size: 1em;
    opacity: 0.9;
    font-style: italic;
    text-shadow: 1px 1px 3px rgba(0,0,0,0.3);
    transition: all 0.3s ease;
}

/* Scrolled Header */
header.scrolled {
    padding: 12px 20px;
}

header.scrolled .logo {
    max-width: 80px;
    padding: 8px;
}

header.scrolled h1 {
    font-size: 1.4em;
    margin-bottom: 2px;
}

header.scrolled .subtitle {
    font-size: 0.9em;
    margin-bottom: 2px;
}

header.scrolled .conference {
    font-size: 0.8em;
}

/* Navigation */
nav {
    background-color: #1e40af;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 99;
}

nav ul {
    list-style: none;
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
}

nav li {
    margin: 0;
}

nav a {
    display: block;
    color: white;
    text-decoration: none;
    padding: 15px 20px;
    transition: background-color 0.3s;
    font-weight: 500;
    font-size: 0.95em;
}

nav a:hover {
    background-color: #1e3a8a;
}

/* Main Content */
main {
    background-color: white;
    margin: 30px auto 0;
    padding: 40px;
    border-radius: 8px 8px 0 0;
    box-shadow: 0 2px 15px rgba(0,0,0,0.1);
}

/* Sections */
section {
    margin-bottom: 50px;
    scroll-margin-top: 150px;
}

section:last-child {
    margin-bottom: 0;
}

h2 {
    color: #1e3a8a;
    font-size: 2em;
    margin-bottom: 20px;
    padding-bottom: 10px;
    border-bottom: 3px solid #3b82f6;
}

h3 {
    color: #1e40af;
    font-size: 1.4em;
    margin: 25px 0 15px 0;
}

p {
    margin-bottom: 15px;
    text-align: justify;
}

a {
    color: #2563eb;
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

/* Button Styles */
.btn {
    display: inline-block;
    padding: 12px 30px;
    background-color: #3b82f6;
    color: white;
    text-decoration: none;
    border-radius: 6px;
    font-weight: 600;
    transition: background-color 0.3s, transform 0.2s;
    margin-top: 15px;
}

.btn:hover {
    background-color: #2563eb;
    text-decoration: none;
    transform: translateY(-2px);
}

.btn-center {
    text-align: center;
    margin-top: 20px;
}

/* Topics Grid */
.topics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 25px;
    margin-top: 25px;
    justify-items: center;
}

.topic-category {
    background-color: #f8fafc;
    padding: 20px;
    border-radius: 8px;
    border-left: 4px solid #3b82f6;
    width: 100%;
    max-width: 450px;
}

.topic-category h3 {
    margin-top: 0;
    font-size: 1.2em;
}

.topic-category ul {
    list-style: none;
    padding-left: 0;
}

.topic-category li {
    padding: 8px 0;
    padding-left: 20px;
    position: relative;
}

.topic-category li:before {
    content: "→";
    position: absolute;
    left: 0;
    color: #3b82f6;
    font-weight: bold;
}

/* Submission Section */
#submission ul {
    list-style: none;
    padding-left: 0;
}

#submission li {
    padding: 10px 0;
    padding-left: 25px;
    position: relative;
}

#submission li:before {
    content: "✓";
    position: absolute;
    left: 0;
    color: #059669;
    font-weight: bold;
    font-size: 1.2em;
}

.submission-link {
    background-color: #dbeafe;
    padding: 20px;
    border-radius: 8px;
    margin-top: 20px;
    text-align: center;
}

/* Important Dates */
.dates-box {
    background-color: #fef3c7;
    padding: 25px;
    border-radius: 8px;
    border-left: 5px solid #f59e0b;
    margin: 20px 0;
}

.dates-box table {
    width: 100%;
    border-collapse: collapse;
}

.dates-box tr {
    border-bottom: 1px solid #fbbf24;
}

.dates-box tr:last-child {
    border-bottom: none;
}

.dates-box td {
    padding: 12px 0;
}

.dates-box td:first-child {
    width: 60%;
}

.note {
    font-style: italic;
    color: #666;
    margin-top: 15px;
    font-size: 0.9em;
}

/* Organizers */
.organizer {
    margin-bottom: 35px;
    padding: 25px;
    background-color: #f0f9ff;
    border-radius: 8px;
    border-left: 4px solid #0284c7;
}

.organizer h3 {
    margin-top: 0;
    color: #0284c7;
}

.organizer p {
    margin-bottom: 10px;
}

.organizer .bio {
    margin-top: 15px;
    text-align: justify;
    color: #555;
}

/* Committee Grid */
.committee-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
    margin-top: 25px;
    justify-items: center;
}

.committee-member {
    background-color: #f8fafc;
    padding: 15px;
    border-radius: 6px;
    border-left: 3px solid #6366f1;
    font-size: 0.95em;
    width: 100%;
    max-width: 320px;
}

/* Structure Section */
#structure ul {
    list-style: none;
    padding-left: 0;
}

#structure li {
    padding: 15px;
    margin-bottom: 10px;
    background-color: #f0fdf4;
    border-radius: 6px;
    border-left: 4px solid #10b981;
}

/* Contact Form Section */
#contact {
    background-color: #f8fafc;
    padding: 30px;
    border-radius: 8px;
    margin-top: 30px;
}

.contact-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 40px;
    margin-top: 25px;
}

.contact-form {
    background-color: white;
    padding: 30px;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: #1e3a8a;
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 12px;
    border: 2px solid #e2e8f0;
    border-radius: 6px;
    font-size: 1em;
    font-family: inherit;
    transition: border-color 0.3s;
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: #3b82f6;
}

.form-group textarea {
    resize: vertical;
    min-height: 120px;
}

.submit-btn {
    background-color: #3b82f6;
    color: white;
    padding: 14px 32px;
    border: none;
    border-radius: 6px;
    font-size: 1em;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.3s;
    width: 100%;
}

.submit-btn:hover {
    background-color: #2563eb;
}

.contact-info {
    background-color: white;
    padding: 30px;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

.contact-info h3 {
    margin-top: 0;
    color: #1e3a8a;
}

.contact-person {
    margin-bottom: 25px;
    padding-bottom: 25px;
    border-bottom: 1px solid #e2e8f0;
}

.contact-person:last-child {
    border-bottom: none;
    margin-bottom: 0;
    padding-bottom: 0;
}

.contact-person strong {
    color: #1e40af;
    font-size: 1.1em;
}

.hidden {
    display: none;
}

/* Footer */
footer {
    background-color: #1e3a8a;
    color: white;
    text-align: center;
    padding: 30px 20px;
}

footer p {
    margin: 5px 0;
    text-align: center;
}

/* Responsive Design */
@media (max-width: 768px) {
    header .header-content {
        gap: 15px;
    }
    
    header .logo {
        max-width: 100px;
        padding: 10px;
    }
    
    header.scrolled .logo {
        max-width: 60px;
        padding: 6px;
    }
    
    header h1 {
        font-size: 1.8em;
    }
    
    header.scrolled h1 {
        font-size: 1.1em;
    }
    
    header .subtitle {
        font-size: 1em;
    }
    
    header.scrolled .subtitle {
        font-size: 0.75em;
    }
    
    header .conference {
        font-size: 0.85em;
    }
    
    header.scrolled .conference {
        font-size: 0.7em;
    }
    
    nav ul {
        flex-direction: column;
    }
    
    nav a {
        padding: 12px 20px;
    }
    
    main {
        padding: 20px;
        margin: 15px;
    }
    
    .topics-grid {
        grid-template-columns: 1fr;
    }
    
    .committee-grid {
        grid-template-columns: 1fr;
    }
    
    .contact-container {
        grid-template-columns: 1fr;
    }
    
    .dates-box table {
        font-size: 0.9em;
    }
    
    .dates-box td:first-child {
        width: 55%;
    }
}

@media (max-width: 480px) {
    header .header-content {
        gap: 10px;
    }
    
    header .logo {
        max-width: 70px;
        padding: 8px;
    }
    
    header.scrolled .logo {
        max-width: 45px;
        padding: 5px;
    }
    
    header h1 {
        font-size: 1.4em;
    }
    
    header.scrolled h1 {
        font-size: 0.95em;
    }
    
    header .subtitle {
        font-size: 0.85em;
    }
    
    header.scrolled .subtitle {
        font-size: 0.65em;
    }
    
    header .conference {
        font-size: 0.75em;
    }
    
    header.scrolled .conference {
        font-size: 0.6em;
    }
    
    main {
        padding: 15px;
        margin: 10px;
    }
    
    h2 {
        font-size: 1.5em;
    }
}