:root {
    --primary-color: #b388ff;
    --secondary-color: #00e5ff;
    --bg-dark: #0a0b1e;
    --bg-card: rgba(30, 30, 45, 0.6);
    --bg-card-hover: rgba(50, 50, 70, 0.8);
    --text-primary: #ffffff;
    --text-secondary: rgba(255, 255, 255, 0.7);
    --accent-gradient: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
}

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

body {
    font-family: 'Roboto', sans-serif;
    background-color: var(--bg-dark);
    color: var(--text-primary);
    line-height: 1.7;
    overflow-x: hidden;
}

/* Language Switching Logic */
:root:not([lang="en"]) .lang-en { display: none !important; }
:root[lang="en"] .lang-zh { display: none !important; }
:root[lang="en"] .lang-en { display: inline-block; }
:root[lang="en"] div.lang-en,
:root[lang="en"] p.lang-en,
:root[lang="en"] h1.lang-en,
:root[lang="en"] h2.lang-en,
:root[lang="en"] h3.lang-en,
:root[lang="en"] section.lang-en,
:root[lang="en"] ul.lang-en { display: block !important; }

/* Background Animation */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: radial-gradient(circle at 15% 50%, rgba(101, 31, 255, 0.1), transparent 30%), radial-gradient(circle at 85% 30%, rgba(0, 229, 255, 0.1), transparent 30%);
    z-index: -1;
}

/* Header */
header {
    position: fixed;
    top: 0;
    width: 100%;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: rgba(10, 11, 30, 0.85);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid rgba(255,255,255,0.05);
    z-index: 1000;
}
.logo {
    text-decoration: none;
    display: flex;
    align-items: center;
}

.logo-img {
    height: 60px; 
    width: auto;
    display: block;
}
.nav-links { display: flex; gap: 2rem; }
.nav-links a { color: var(--text-secondary); text-decoration: none; font-weight: 500; transition: color 0.3s; font-size: 0.95rem; }
.nav-links a:hover { color: var(--secondary-color); }
.auth-btn { background: var(--accent-gradient); border: none; padding: 0.6rem 1.8rem; border-radius: 50px; color: #000; font-weight: 700; cursor: pointer; text-decoration: none; transition: all 0.3s; box-shadow: 0 4px 15px rgba(179, 136, 255, 0.3); }
.auth-btn:hover { transform: translateY(-2px); box-shadow: 0 6px 20px rgba(0, 229, 255, 0.4); }

/* Modal Styles */
.modal {
    display: none; 
    position: fixed; 
    z-index: 2000; 
    left: 0;
    top: 0;
    width: 100%; 
    height: 100%; 
    overflow: auto; 
    background-color: rgba(0,0,0,0.6); 
    backdrop-filter: blur(5px);
}
.modal-content {
    background-color: #1e1e2d;
    margin: 5% auto; 
    padding: 2rem;
    border: 1px solid rgba(255,255,255,0.1);
    width: 90%;
    max-width: 400px;
    border-radius: 12px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.5);
    animation: fadeIn 0.3s;
}
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(-20px); }
    to { opacity: 1; transform: translateY(0); }
}
.close {
    color: #aaa;
    float: right;
    font-size: 28px;
    font-weight: bold;
    cursor: pointer;
}
.close:hover { color: #fff; }
.form-group { margin-bottom: 1.5rem; }
.form-group label { display: block; margin-bottom: 0.5rem; color: var(--text-secondary); }
.form-group input { 
    width: 100%; padding: 0.8rem; border-radius: 6px; border: 1px solid rgba(255,255,255,0.2); 
    background: rgba(0,0,0,0.2); color: #fff; font-size: 1rem;
}
.form-group input:focus { border-color: var(--secondary-color); outline: none; }
.modal-title { margin-bottom: 1.5rem; text-align: center; color: var(--primary-color); }
.btn-block { width: 100%; }

/* Role Toggle Buttons */
.role-btn {
    flex: 1;
    padding: 0.8rem;
    background: rgba(255,255,255,0.05);
    border: 1px solid rgba(255,255,255,0.1);
    color: var(--text-secondary);
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.3s;
}
.role-btn.active {
    background: var(--primary-color);
    color: #000;
    border-color: var(--primary-color);
    font-weight: bold;
}

/* Main Layout */
main { max-width: 1200px; margin: 0 auto; padding: 0 1.5rem 4rem; }
.hero { text-align: center; padding: 160px 0 100px; position: relative; }
.hero h1 { font-size: 4rem; font-weight: 900; line-height: 1.1; margin-bottom: 1.5rem; background: linear-gradient(180deg, #fff 0%, #aaa 100%); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
.hero p { font-size: 1.25rem; color: var(--text-secondary); max-width: 700px; margin: 0 auto 3rem; }
.hero-btns { display: flex; gap: 1rem; justify-content: center; }
.btn-primary { padding: 1rem 2.5rem; background: var(--accent-gradient); color: #0a0b1e; font-weight: bold; border-radius: 8px; text-decoration: none; font-size: 1.1rem; transition: transform 0.2s; cursor: pointer; border:none; }
.btn-secondary { padding: 1rem 2.5rem; background: rgba(255,255,255,0.05); color: #fff; border: 1px solid rgba(255,255,255,0.1); font-weight: bold; border-radius: 8px; text-decoration: none; font-size: 1.1rem; transition: background 0.2s; }
.btn-primary:hover { transform: scale(1.05); }
.btn-secondary:hover { background: rgba(255,255,255,0.1); }
section { margin-bottom: 8rem; }
section h2 { font-size: 2.2rem; margin-bottom: 3rem; text-align: center; position: relative; display: inline-block; left: 50%; transform: translateX(-50%); }
section h2::after { content: ''; display: block; width: 60px; height: 4px; background: var(--secondary-color); margin: 1rem auto 0; border-radius: 2px; }
.grid-2 { display: grid; gap: 2rem; grid-template-columns: repeat(auto-fit, minmax(400px, 1fr)); }
.card { background: var(--bg-card); border: 1px solid rgba(255,255,255,0.08); padding: 2rem; border-radius: 16px; transition: all 0.3s ease; }
.card:hover { transform: translateY(-5px); border-color: var(--primary-color); box-shadow: 0 10px 30px rgba(0,0,0,0.3); }
.card h3 { color: var(--secondary-color); margin-bottom: 1rem; font-size: 1.3rem; display: flex; align-items: center; gap: 0.5rem; }
.card p { font-size: 0.95rem; margin-bottom: 0; }
.timeline { position: relative; max-width: 800px; margin: 0 auto; }
.timeline::before { content: ''; position: absolute; left: 0; top: 0; height: 100%; width: 2px; background: rgba(255,255,255,0.1); }
.timeline-item { padding-left: 3rem; position: relative; margin-bottom: 3rem; }
.timeline-item::before { content: ''; position: absolute; left: -5px; top: 5px; width: 12px; height: 12px; border-radius: 50%; background: var(--primary-color); box-shadow: 0 0 10px var(--primary-color); }
.timeline-date { color: var(--secondary-color); font-weight: bold; margin-bottom: 0.5rem; font-family: monospace; font-size: 1.1rem; }
footer { background: #050510; padding: 3rem 1rem; text-align: center; color: var(--text-secondary); border-top: 1px solid rgba(255,255,255,0.05); }
@media (max-width: 768px) { .hero h1 { font-size: 2.5rem; } .nav-links { display: none; } .grid-2 { grid-template-columns: 1fr; } .timeline::before { left: 20px; } .timeline-item { padding-left: 4rem; } .timeline-item::before { left: 15px; } }