/* Reset & Base */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: #222;
    background: #f0f2f5;
    transition: background 0.3s, color 0.3s;
}
a { text-decoration: none; color: inherit; }
ul, ol { list-style: none; }
img { max-width: 100%; height: auto; display: block; }
button { cursor: pointer; border: none; background: none; font: inherit; }
h1, h2, h3, h4 { line-height: 1.2; }
/* Container */
main { max-width: 1280px; margin: 0 auto; padding: 0 20px; }
/* Header & Nav */
header {
    background: rgba(255,255,255,0.75);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    position: sticky;
    top: 0;
    z-index: 1000;
    border-bottom: 1px solid rgba(0,0,0,0.05);
    transition: background 0.3s;
}
nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    max-width: 1280px;
    margin: 0 auto;
    padding: 12px 20px;
    flex-wrap: wrap;
}
nav ul {
    display: flex;
    gap: 28px;
    font-weight: 500;
}
nav ul li a {
    padding: 6px 0;
    position: relative;
    transition: color 0.3s;
}
nav ul li a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: #ff6600;
    transition: width 0.3s;
}
nav ul li a:hover::after { width: 100%; }
nav ul li a:hover { color: #ff6600; }
#darkModeToggle, #mobileMenuToggle {
    font-size: 1.4rem;
    padding: 6px 10px;
    border-radius: 8px;
    transition: background 0.2s;
}
#darkModeToggle:hover, #mobileMenuToggle:hover { background: rgba(0,0,0,0.05); }
#mobileMenuToggle { display: none; }
/* Hero Section */
#hero {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 40px;
    padding: 80px 0 60px;
    flex-wrap: wrap;
}
#hero > div:first-child { flex: 1 1 400px; }
#hero > div:last-child { flex: 1 1 400px; }
#hero h1 {
    font-size: clamp(2rem, 5vw, 3.2rem);
    background: linear-gradient(135deg, #ff6600, #ff8c00, #ffaa00);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 20px;
}
#hero p {
    font-size: 1.2rem;
    color: #555;
    margin-bottom: 30px;
    max-width: 500px;
}
#hero a {
    display: inline-block;
    padding: 14px 40px;
    background: linear-gradient(135deg, #ff6600, #ff8c00);
    color: #fff;
    border-radius: 50px;
    font-weight: 600;
    transition: transform 0.3s, box-shadow 0.3s;
    box-shadow: 0 8px 20px rgba(255,102,0,0.3);
}
#hero a:hover { transform: translateY(-3px); box-shadow: 0 12px 28px rgba(255,102,0,0.4); }
#hero img {
    border-radius: 24px;
    box-shadow: 0 20px 40px rgba(0,0,0,0.1);
    transition: transform 0.5s;
}
#hero img:hover { transform: scale(1.02); }
/* Sections */
section {
    padding: 60px 0;
    opacity: 0;
    transform: translateY(30px);
    animation: fadeInUp 0.7s ease forwards;
}
@keyframes fadeInUp {
    to { opacity: 1; transform: translateY(0); }
}
section:nth-child(2) { animation-delay: 0.1s; }
section:nth-child(3) { animation-delay: 0.2s; }
section:nth-child(4) { animation-delay: 0.3s; }
section:nth-child(5) { animation-delay: 0.4s; }
section:nth-child(6) { animation-delay: 0.5s; }
section:nth-child(7) { animation-delay: 0.6s; }
section:nth-child(8) { animation-delay: 0.7s; }
section:nth-child(9) { animation-delay: 0.8s; }
section:nth-child(10) { animation-delay: 0.9s; }
section h2 {
    font-size: clamp(1.8rem, 4vw, 2.6rem);
    text-align: center;
    margin-bottom: 16px;
    background: linear-gradient(135deg, #ff6600, #ff8c00);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
section > p {
    text-align: center;
    color: #666;
    max-width: 700px;
    margin: 0 auto 40px;
    font-size: 1.05rem;
}
/* Cards Grid - Events & Platform */
#events > div, #platform > div {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 24px;
}
article {
    background: rgba(255,255,255,0.6);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border-radius: 20px;
    padding: 28px 20px;
    text-align: center;
    box-shadow: 0 8px 20px rgba(0,0,0,0.04);
    transition: transform 0.3s, box-shadow 0.3s, background 0.3s;
    border: 1px solid rgba(255,255,255,0.3);
}
article:hover {
    transform: translateY(-8px);
    box-shadow: 0 16px 32px rgba(255,102,0,0.12);
    background: rgba(255,255,255,0.85);
}
article h3 {
    font-size: 1.3rem;
    margin-bottom: 10px;
    color: #1a1a2e;
}
article p { color: #555; font-size: 0.95rem; }
/* About */
#about {
    background: rgba(255,255,255,0.5);
    backdrop-filter: blur(6px);
    border-radius: 24px;
    padding: 50px 30px;
    text-align: center;
    max-width: 900px;
    margin: 0 auto;
}
#about p { margin-bottom: 12px; color: #444; }
/* Help Center - FAQ */
#help > div {
    max-width: 800px;
    margin: 0 auto;
}
details {
    background: rgba(255,255,255,0.5);
    backdrop-filter: blur(4px);
    border-radius: 16px;
    margin-bottom: 12px;
    padding: 14px 20px;
    border: 1px solid rgba(0,0,0,0.04);
    transition: background 0.3s, box-shadow 0.3s;
}
details[open] { background: rgba(255,255,255,0.8); box-shadow: 0 4px 12px rgba(0,0,0,0.04); }
summary {
    font-weight: 600;
    cursor: pointer;
    padding: 4px 0;
    color: #1a1a2e;
    transition: color 0.2s;
}
summary:hover { color: #ff6600; }
details p {
    margin-top: 12px;
    color: #555;
    padding-left: 8px;
    border-left: 3px solid #ff6600;
}
/* HowTo */
#howto ol {
    max-width: 600px;
    margin: 0 auto;
    counter-reset: step;
    list-style: none;
}
#howto ol li {
    counter-increment: step;
    padding: 12px 0 12px 48px;
    position: relative;
    font-size: 1.05rem;
    border-bottom: 1px solid rgba(0,0,0,0.04);
}
#howto ol li::before {
    content: counter(step);
    position: absolute;
    left: 0;
    top: 10px;
    width: 32px;
    height: 32px;
    background: linear-gradient(135deg, #ff6600, #ff8c00);
    color: #fff;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 0.9rem;
}
/* Knowledge */
#knowledge ul {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 16px;
    max-width: 800px;
    margin: 0 auto;
}
#knowledge ul li {
    background: rgba(255,255,255,0.5);
    backdrop-filter: blur(4px);
    border-radius: 16px;
    padding: 16px 20px;
    text-align: center;
    transition: transform 0.3s, background 0.3s;
    border: 1px solid rgba(255,255,255,0.2);
}
#knowledge ul li:hover { transform: translateY(-4px); background: rgba(255,255,255,0.8); }
#knowledge ul li a { color: #1a1a2e; font-weight: 500; }
#knowledge ul li a:hover { color: #ff6600; }
/* Contact */
#contact address {
    max-width: 500px;
    margin: 0 auto;
    background: rgba(255,255,255,0.5);
    backdrop-filter: blur(4px);
    border-radius: 20px;
    padding: 30px;
    text-align: center;
    font-style: normal;
}
#contact address p { margin-bottom: 8px; color: #444; }
/* Footer */
footer {
    background: #1a1a2e;
    color: #ccc;
    padding: 30px 20px;
    text-align: center;
    margin-top: 40px;
}
footer nav ul {
    display: flex;
    justify-content: center;
    gap: 24px;
    flex-wrap: wrap;
    margin-bottom: 16px;
}
footer nav ul li a { color: #aaa; transition: color 0.3s; }
footer nav ul li a:hover { color: #ff6600; }
footer p { font-size: 0.9rem; }
/* Back to Top */
#backToTop {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: linear-gradient(135deg, #ff6600, #ff8c00);
    color: #fff;
    font-size: 1.6rem;
    display: none;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 14px rgba(255,102,0,0.3);
    transition: transform 0.3s, box-shadow 0.3s;
    z-index: 999;
}
#backToTop:hover { transform: scale(1.1); box-shadow: 0 6px 20px rgba(255,102,0,0.4); }
/* Dark Mode */
body.dark-mode {
    background: #121212;
    color: #e0e0e0;
}
body.dark-mode header {
    background: rgba(18,18,18,0.8);
    border-bottom-color: rgba(255,255,255,0.05);
}
body.dark-mode nav ul li a { color: #ccc; }
body.dark-mode nav ul li a:hover { color: #ff8c00; }
body.dark-mode #hero p { color: #aaa; }
body.dark-mode section > p { color: #aaa; }
body.dark-mode article {
    background: rgba(30,30,30,0.6);
    border-color: rgba(255,255,255,0.05);
}
body.dark-mode article:hover { background: rgba(40,40,40,0.8); }
body.dark-mode article h3 { color: #f0f0f0; }
body.dark-mode article p { color: #aaa; }
body.dark-mode #about { background: rgba(30,30,30,0.5); }
body.dark-mode #about p { color: #bbb; }
body.dark-mode details {
    background: rgba(30,30,30,0.5);
    border-color: rgba(255,255,255,0.04);
}
body.dark-mode details[open] { background: rgba(40,40,40,0.7); }
body.dark-mode summary { color: #e0e0e0; }
body.dark-mode details p { color: #aaa; }
body.dark-mode #howto ol li { border-bottom-color: rgba(255,255,255,0.04); color: #ccc; }
body.dark-mode #knowledge ul li { background: rgba(30,30,30,0.5); border-color: rgba(255,255,255,0.04); }
body.dark-mode #knowledge ul li a { color: #ddd; }
body.dark-mode #knowledge ul li:hover { background: rgba(40,40,40,0.7); }
body.dark-mode #contact address { background: rgba(30,30,30,0.5); }
body.dark-mode #contact address p { color: #bbb; }
body.dark-mode #darkModeToggle, body.dark-mode #mobileMenuToggle { color: #eee; }
body.dark-mode #darkModeToggle:hover, body.dark-mode #mobileMenuToggle:hover { background: rgba(255,255,255,0.05); }
/* Responsive */
@media (max-width: 768px) {
    #mobileMenuToggle { display: block; }
    nav ul {
        display: none;
        flex-direction: column;
        width: 100%;
        gap: 0;
        background: rgba(255,255,255,0.95);
        backdrop-filter: blur(12px);
        border-radius: 16px;
        padding: 12px 0;
        margin-top: 12px;
    }
    body.dark-mode nav ul { background: rgba(20,20,20,0.95); }
    nav ul.active { display: flex; }
    nav ul li a { padding: 12px 20px; display: block; }
    nav ul li a::after { display: none; }
    #hero { padding: 40px 0; flex-direction: column; text-align: center; }
    #hero p { margin-left: auto; margin-right: auto; }
    #hero a { margin: 0 auto; }
    #events > div, #platform > div { grid-template-columns: 1fr; }
    #knowledge ul { grid-template-columns: 1fr; }
    #about { padding: 30px 20px; }
    #backToTop { bottom: 20px; right: 20px; width: 42px; height: 42px; font-size: 1.4rem; }
}
@media (max-width: 480px) {
    main { padding: 0 12px; }
    section { padding: 40px 0; }
    #hero h1 { font-size: 1.8rem; }
    #hero p { font-size: 1rem; }
    article { padding: 20px 16px; }
    details { padding: 12px 16px; }
    #howto ol li { padding-left: 44px; font-size: 0.95rem; }
    footer nav ul { gap: 16px; }
}
/* Smooth scroll for anchor links (no JS needed) */
@media (prefers-reduced-motion: no-preference) {
    html { scroll-behavior: smooth; }
}