/* ===== VARIABLES – LIGHT MODE ===== */
:root {
    --bg-primary: #ffffff;
    --bg-card: #f8fafc;
    --text-primary: #1e293b;
    --text-muted: #64748b;
    --accent-primary: #2563eb;
    --accent-secondary: #7c3aed;
    --header-bg: rgba(255, 255, 255, 0.95);
    --header-text: #1e293b;
    --shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
    --border-radius: 8px;
    --font-heading: 'Poppins', sans-serif;
    --font-body: 'Open Sans', sans-serif;
}

/* ===== DARK MODE OVERRIDES ===== */
body.dark-mode {
    --bg-primary: #000000;
    --bg-card: #1e1e1e;
    --text-primary: #f0f0f0;
    --text-muted: #a0a0a0;
    --accent-primary: #00D4FF;
    --accent-secondary: #FF4D6D;
    --header-bg: rgba(0, 0, 0, 0.95);
    --header-text: #f0f0f0;
    --shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
}

/* ===== RESET ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-body);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
    position: relative;
}

.container {
    width: 90%;
    max-width: 1200px;
    margin: 0 auto;
}

/* ===== PROGRESS BAR ===== */
.progress-bar {
    position: fixed;
    top: 0;
    left: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--accent-primary), var(--accent-secondary));
    width: 0%;
    z-index: 1000;
    transition: width 0.1s;
}

/* ===== HEADER ===== */
.header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background-color: var(--header-bg);
    backdrop-filter: blur(5px);
    z-index: 100;
    padding: 1rem 0;
    transition: background-color 0.3s;
    box-shadow: var(--shadow);
}

.header-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    position: relative;
}

.logo {
    font-size: 1.8rem;
    font-weight: 700;
    font-family: var(--font-heading);
    color: var(--header-text);
}

.logo span {
    color: var(--accent-primary);
}

/* Header right section - contains theme toggle and hamburger */
.header-right {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Theme toggle button - always visible */
.theme-toggle {
    background: none;
    border: none;
    font-size: 1.3rem;
    color: var(--header-text);
    cursor: pointer;
    padding: 0.5rem;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: color 0.2s, background-color 0.2s;
    border-radius: 50%;
}

.theme-toggle:hover {
    color: var(--accent-primary);
    background-color: rgba(0, 0, 0, 0.05);
}

body.dark-mode .theme-toggle:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

/* Hamburger button */
.hamburger {
    display: none;
    font-size: 2rem;
    background: none;
    border: none;
    color: var(--header-text);
    cursor: pointer;
    padding: 0.5rem;
    z-index: 101;
}

/* Navigation wrapper - contains nav only */
.nav-wrapper {
    display: flex;
    align-items: center;
}

.nav ul {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav a {
    text-decoration: none;
    color: var(--header-text);
    font-weight: 600;
    transition: color 0.2s;
}

.nav a:hover,
.nav a.active {
    color: var(--accent-primary);
}

/* ===== BACK TO TOP BUTTON ===== */
.back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background: var(--accent-primary);
    color: white;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    border: none;
    cursor: pointer;
    font-size: 1.5rem;
    display: none;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
    transition: all 0.3s ease;
    z-index: 999;
    opacity: 0;
    visibility: hidden;
}

.back-to-top.show {
    display: flex !important;
    opacity: 1;
    visibility: visible;
}

.back-to-top:hover {
    background: var(--accent-secondary);
    transform: scale(1.1);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.4);
}

body.dark-mode .back-to-top {
    box-shadow: 0 4px 15px rgba(0, 212, 255, 0.3);
}

/* ===== HERO SECTION ===== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    text-align: center;
    padding-top: 80px;
    background: 
        linear-gradient(rgba(0, 0, 0, 0.6), rgba(0, 0, 0, 0.6)),
        url('../images/hero-bg.jpg') center/cover no-repeat;
    color: #ffffff;
    position: relative;
    background-attachment: fixed;
}

body.dark-mode .hero {
    background: 
        linear-gradient(rgba(0, 0, 0, 0.7), rgba(0, 0, 0, 0.7)),
        url('../images/hero-bg.jpg') center/cover no-repeat;
    background-attachment: fixed;
}

.hero-content {
    position: relative;
    z-index: 2;
    width: 100%;
    max-width: 900px;
    margin: 0 auto;
}

.hero h1 {
    font-size: 3.5rem;
    margin-bottom: 1rem;
    font-weight: 700;
    color: #ffffff;
    line-height: 1.2;
    text-shadow: 2px 2px 8px rgba(0, 0, 0, 0.5);
}

.hero h1 span {
    color: var(--accent-primary);
    text-shadow: 2px 2px 8px rgba(0, 0, 0, 0.5);
}

.hero-subtitle {
    font-size: 1.4rem;
    margin-bottom: 1.5rem;
    color: #ffffff;
    font-weight: 400;
    text-shadow: 1px 1px 4px rgba(0, 0, 0, 0.5);
}

.hero-details {
    display: flex;
    justify-content: center;
    gap: 2.5rem;
    margin-bottom: 1.5rem;
    font-size: 1.1rem;
    color: #ffffff;
    flex-wrap: wrap;
    text-shadow: 1px 1px 3px rgba(0, 0, 0, 0.5);
}

.hero-details i {
    color: var(--accent-primary);
    margin-right: 0.5rem;
    filter: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.5));
}

.hero-audience {
    font-size: 1.2rem;
    margin-bottom: 2rem;
    background: rgba(0, 0, 0, 0.4);
    display: inline-block;
    padding: 0.6rem 2rem;
    border-radius: 50px;
    color: #ffffff;
    border: 1px solid rgba(255, 255, 255, 0.2);
    font-weight: 500;
    backdrop-filter: blur(5px);
    text-shadow: 1px 1px 3px rgba(0, 0, 0, 0.5);
}

.hero .countdown {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin-bottom: 2.5rem;
    flex-wrap: wrap;
}

.hero .countdown-item {
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
    padding: 1rem 1.8rem;
    border-radius: 12px;
    min-width: 100px;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.3);
    border: 1px solid rgba(255, 255, 255, 0.15);
}

.hero .countdown-number {
    display: block;
    font-size: 2.8rem;
    font-weight: 700;
    font-family: var(--font-heading);
    color: var(--accent-primary);
    line-height: 1;
    margin-bottom: 0.3rem;
    text-shadow: 0 2px 5px rgba(0, 0, 0, 0.5);
}

.hero .countdown-label {
    font-size: 0.9rem;
    color: rgba(255, 255, 255, 0.95);
    text-transform: uppercase;
    letter-spacing: 1px;
    text-shadow: 0 1px 3px rgba(0, 0, 0, 0.5);
}

.hero .btn-primary {
    background-color: var(--accent-primary);
    color: white;
    padding: 1rem 3rem;
    font-size: 1.2rem;
    font-weight: 600;
    border-radius: 50px;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.3);
    border: none;
    transition: all 0.3s ease;
    display: inline-block;
    text-decoration: none;
}

.hero .btn-primary:hover {
    background-color: var(--accent-secondary);
    transform: translateY(-3px);
    box-shadow: 0 12px 25px rgba(0, 0, 0, 0.4);
}

body.dark-mode .hero .btn-primary {
    background-color: var(--accent-primary);
    color: #0a0f1f;
}

body.dark-mode .hero .btn-primary:hover {
    background-color: var(--accent-secondary);
}

/* ===== BUTTONS ===== */
.btn {
    display: inline-block;
    padding: 1rem 2.5rem;
    border-radius: 50px;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s;
    border: none;
    cursor: pointer;
    font-family: var(--font-heading);
}

.btn-primary {
    background-color: var(--accent-primary);
    color: white;
    box-shadow: 0 4px 14px rgba(37, 99, 235, 0.3);
}

.btn-primary:hover {
    background-color: var(--accent-secondary);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(37, 99, 235, 0.4);
}

.btn-outline {
    background: transparent;
    border: 2px solid var(--accent-primary);
    color: var(--accent-primary);
}

.btn-outline:hover {
    background: var(--accent-primary);
    color: white;
}

.btn-block {
    display: block;
    width: 100%;
}

/* ===== SECTIONS ===== */
section {
    padding: 5rem 0;
}

.section-title {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    font-family: var(--font-heading);
    color: var(--accent-primary);
    position: relative;
}

.section-title::after {
    content: '';
    display: block;
    width: 80px;
    height: 4px;
    background: var(--accent-primary);
    margin: 1rem auto 0;
    border-radius: 2px;
}

.fade-in {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ===== SCHEDULE ===== */
.schedule-tabs {
    display: flex;
    justify-content: center;
    gap: 3rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.tab-button {
    background: transparent;
    border: 2px solid var(--accent-primary);
    color: var(--accent-primary);
    padding: 0.8rem 2.5rem;
    border-radius: 50px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    font-size: 1.1rem;
}

.tab-button.active,
.tab-button:hover {
    background: var(--accent-primary);
    color: white;
}

.schedule-content {
    max-width: 800px;
    margin: 0 auto;
}

.schedule-content.hidden {
    display: none;
}

.schedule-item {
    display: flex;
    gap: 2rem;
    padding: 1.5rem;
    background: var(--bg-card);
    border-radius: var(--border-radius);
    margin-bottom: 1rem;
    box-shadow: var(--shadow);
    transition: background 0.3s;
}

.schedule-item.current {
    background: rgba(37, 99, 235, 0.1);
    border-left: 4px solid var(--accent-secondary);
}

.schedule-item .time {
    font-weight: 700;
    color: var(--accent-primary);
    min-width: 150px;
}

.schedule-item h3 {
    font-size: 1.2rem;
    margin-bottom: 0.3rem;
    color: var(--text-primary);
}

.schedule-item p {
    color: var(--text-muted);
}

/* ===== SPEAKERS ===== */
.speakers-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
}

.speaker-card {
    background: var(--bg-card);
    border-radius: var(--border-radius);
    padding: 2rem;
    text-align: center;
    box-shadow: var(--shadow);
    transition: transform 0.3s;
}

.speaker-card:hover {
    transform: translateY(-8px);
}

.speaker-photo {
    width: 120px;
    height: 120px;
    border-radius: 50%;
    object-fit: cover;
    border: 3px solid var(--accent-primary);
    margin-bottom: 1rem;
}

.speaker-card h3 {
    margin-bottom: 0.3rem;
    font-size: 1.3rem;
    color: var(--text-primary);
}

.speaker-role {
    color: var(--accent-primary);
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.speaker-topic {
    color: var(--text-muted);
    font-size: 0.95rem;
    margin-bottom: 1rem;
}

.speaker-social {
    display: flex;
    justify-content: center;
    gap: 1rem;
}

.speaker-social a {
    color: var(--text-muted);
    font-size: 1.2rem;
    transition: color 0.2s;
}

.speaker-social a:hover {
    color: var(--accent-primary);
}

/* ===== VENUE ===== */
.venue-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    background: var(--bg-card);
    border-radius: var(--border-radius);
    padding: 2rem;
    box-shadow: var(--shadow);
}

.venue-info h3 {
    margin-bottom: 1rem;
    font-size: 1.8rem;
    color: var(--text-primary);
}

.venue-info p {
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.8rem;
    color: var(--text-primary);
}

.venue-info i {
    color: var(--accent-primary);
    width: 1.5rem;
}

.venue-map iframe {
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    width: 100%;
    height: 300px;
    border: 0;
}

/* ===== SPONSORS ===== */
.sponsors {
    background: rgba(0, 0, 0, 0.02);
    padding: 5rem 0;
}

.sponsor-grid {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 2rem;
    margin-top: 2rem;
}

.sponsor-item {
    background: var(--bg-card);
    padding: 1rem 2rem;
    border-radius: 50px;
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--accent-primary);
    border: 1px solid var(--accent-primary);
    transition: transform 0.2s, box-shadow 0.2s;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.sponsor-item i {
    font-size: 1.2rem;
}

.sponsor-item:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow);
}

/* ===== REGISTRATION ===== */
.register-content {
    max-width: 600px;
    margin: 0 auto;
    background: var(--bg-card);
    padding: 2.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
}

.register-content p {
    text-align: center;
    margin-bottom: 2rem;
    color: var(--text-primary);
}

.register-form {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.form-group {
    display: flex;
    flex-direction: column;
}

.form-group label {
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: var(--accent-primary);
}

.form-group input,
.form-group select,
.form-group textarea {
    padding: 0.8rem;
    border: none;
    border-radius: var(--border-radius);
    background: rgba(0, 0, 0, 0.05);
    color: var(--text-primary);
    font-family: var(--font-body);
    border: 1px solid transparent;
    transition: border 0.2s, box-shadow 0.2s;
    width: 100%;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border: 1px solid var(--accent-primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-group input::placeholder,
.form-group textarea::placeholder {
    color: var(--text-muted);
    opacity: 0.7;
}

.form-note {
    font-size: 0.9rem;
    color: var(--text-muted);
    margin-top: 0.5rem;
    text-align: center;
}

/* Dark mode form improvements */
body.dark-mode .form-group input,
body.dark-mode .form-group select,
body.dark-mode .form-group textarea {
    background-color: #2d2d2d;
    color: #f0f0f0;
    border: 1px solid #444;
}

body.dark-mode .form-group input:focus,
body.dark-mode .form-group select:focus,
body.dark-mode .form-group textarea:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 2px rgba(0, 212, 255, 0.2);
}

body.dark-mode .form-group label {
    color: var(--accent-primary);
}

body.dark-mode .register-content {
    background-color: #1a1a1a;
}

/* ===== FOOTER ===== */
.footer {
    background-color: var(--bg-card);
    padding: 2rem 0;
    border-top: 1px solid var(--text-muted);
}

.footer-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.footer-container p {
    color: var(--text-primary);
}

.footer-links a {
    color: var(--text-primary);
    font-size: 1.5rem;
    margin-left: 1rem;
    transition: color 0.2s;
}

.footer-links a:hover {
    color: var(--accent-primary);
}

/* ===== RESPONSIVE ===== */
@media (max-width: 768px) {
    .header-container {
        justify-content: space-between;
    }

    .hamburger {
        display: block;
    }

    .nav-wrapper {
        display: none;
        width: 100%;
        flex-direction: column;
        align-items: flex-start;
        padding: 1rem 0;
        order: 3;
    }

    .nav-wrapper.show {
        display: flex;
    }

    .nav ul {
        flex-direction: column;
        width: 100%;
        gap: 0.5rem;
    }

    .nav ul li {
        width: 100%;
    }

    .nav ul li a {
        display: block;
        padding: 0.5rem 0;
    }

    .hero h1 {
        font-size: 2.2rem;
    }

    .hero-subtitle {
        font-size: 1.1rem;
    }

    .hero-details {
        flex-direction: column;
        gap: 0.8rem;
    }

    .hero .countdown-item {
        min-width: 70px;
        padding: 0.8rem 1rem;
    }

    .hero .countdown-number {
        font-size: 2rem;
    }

    .hero-audience {
        font-size: 1rem;
        padding: 0.5rem 1.2rem;
    }

    .hero .btn-primary {
        padding: 0.8rem 2rem;
        font-size: 1rem;
    }

    .schedule-tabs {
        gap: 1.5rem;
    }
    
    .tab-button {
        padding: 0.6rem 1.5rem;
        font-size: 1rem;
    }

    .schedule-item {
        flex-direction: column;
        gap: 0.5rem;
    }

    .schedule-item .time {
        min-width: auto;
    }

    .venue-content {
        grid-template-columns: 1fr;
    }

    .sponsor-grid {
        gap: 1rem;
    }
    
    .sponsor-item {
        padding: 0.8rem 1.5rem;
        font-size: 1rem;
    }

    .footer-container {
        flex-direction: column;
        text-align: center;
    }

    .footer-links a {
        margin: 0 0.5rem;
    }
}

@media (max-width: 480px) {
    .hero h1 {
        font-size: 1.8rem;
    }

    .hero .countdown {
        gap: 0.8rem;
    }

    .hero .countdown-item {
        min-width: 60px;
        padding: 0.6rem 0.8rem;
    }

    .hero .countdown-number {
        font-size: 1.5rem;
    }
    
    .sponsor-item {
        width: 100%;
        justify-content: center;
    }
}