/* ===== 背景 ===== */
body {
    min-height: 100vh;
    overflow-x: hidden;
    font-family: 'Exo 2', sans-serif;
    color: white;
}

.tech-bg {
    position: fixed;
    top: 0; left: 0;
    width: 100%; height: 100%;
    z-index: -1;
    overflow: hidden;
}

.tech-bg::before {
    content: '';
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    background: #0a1929;
    background-size: cover;
    z-index: 0;
}

.bg-video {
    position: absolute;
    top: 50%; left: 50%;
    transform: translate(-50%, -50%);
    min-width: 100%; min-height: 100%;
    width: auto; height: auto;
    object-fit: cover;
    z-index: 0;
    opacity: 0;
    transition: opacity 1.2s ease;
}

.bg-video.loaded {
    opacity: 1;
}

.tech-bg::after {
    content: '';
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    background: rgba(0, 0, 0, 0);
    z-index: 1;
}

.tech-grid {
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    background-image:
        linear-gradient(rgba(0, 243, 255, 0.04) 1px, transparent 1px),
        linear-gradient(90deg, rgba(0, 243, 255, 0.04) 1px, transparent 1px);
    background-size: 50px 50px;
    opacity: 0.3;
    z-index: 2;
}

/* ===== 通用卡片 ===== */
.tech-card {
    background: rgba(16, 18, 27, 0.8);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(0, 243, 255, 0.2);
    border-radius: 12px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
    transition: all 0.3s ease;
}

/* ===== 主题变量 ===== */
:root {
    --theme-bg: #0a1929;
    --theme-bg-darker: #051018;
    --theme-text: #ffffff;
    --theme-primary: #0288d1;
    --theme-secondary: #26c6da;
    --theme-accent: #00acc1;
    --theme-card-bg: rgba(10, 25, 41, 0.9);
    --theme-font: 'Inter', sans-serif;
    --theme-title-font: 'Orbitron', sans-serif;
    --theme-border: rgba(2, 136, 209, 0.35);
    --theme-gradient: linear-gradient(135deg, #0288d1, #26c6da);
}

.theme-ocean {
    --theme-bg: #0a1929;
    --theme-bg-darker: #051018;
    --theme-primary: #0288d1;
    --theme-secondary: #26c6da;
    --theme-card-bg: rgba(10, 25, 41, 0.9);
    --theme-border: rgba(2, 136, 209, 0.35);
    --theme-gradient: linear-gradient(135deg, #0288d1, #26c6da);
}

.theme-cyberpunk {
    --theme-bg: #1a0a2e;
    --theme-bg-darker: #0f0520;
    --theme-primary: #ff006e;
    --theme-secondary: #00d9ff;
    --theme-card-bg: rgba(26, 10, 46, 0.85);
    --theme-border: rgba(255, 0, 110, 0.35);
    --theme-gradient: linear-gradient(135deg, #ff006e, #00d9ff);
}

.theme-forest {
    --theme-bg: #0a1f0a;
    --theme-bg-darker: #051005;
    --theme-primary: #4caf50;
    --theme-secondary: #ffd700;
    --theme-card-bg: rgba(10, 31, 10, 0.9);
    --theme-border: rgba(76, 175, 80, 0.4);
    --theme-gradient: linear-gradient(135deg, #4caf50, #ffd700);
}

.theme-sunset {
    --theme-bg: #1a0f0a;
    --theme-bg-darker: #100805;
    --theme-primary: #ff6b35;
    --theme-secondary: #9b59b6;
    --theme-card-bg: rgba(26, 15, 10, 0.9);
    --theme-border: rgba(255, 107, 53, 0.4);
    --theme-gradient: linear-gradient(135deg, #ff6b35, #9b59b6);
}

/* 主题背景 */
.theme-cyberpunk .tech-bg,
.theme-forest .tech-bg,
.theme-ocean .tech-bg,
.theme-sunset .tech-bg {
    background: radial-gradient(circle at 20% 30%, var(--theme-primary) 0%, transparent 30%),
                radial-gradient(circle at 80% 70%, var(--theme-secondary) 0%, transparent 30%),
                var(--theme-bg-darker);
    position: fixed; top: 0; left: 0; width: 100%; height: 100%; z-index: -1; opacity: 0.3;
}

.theme-cyberpunk .tech-grid,
.theme-forest .tech-grid,
.theme-ocean .tech-grid,
.theme-sunset .tech-grid {
    background-image:
        linear-gradient(var(--theme-border) 1px, transparent 1px),
        linear-gradient(90deg, var(--theme-border) 1px, transparent 1px);
    background-size: 50px 50px;
    position: absolute; top: 0; left: 0; width: 100%; height: 100%; opacity: 0.1;
}

/* 活动页 */
.activity-slider { position: relative; overflow: hidden; height: 220px; }
.activity-slide { display: none; animation: fadeInOut 0.5s ease-in-out; }
.activity-slide.active { display: block; }
@keyframes fadeInOut {
    from { opacity: 0; transform: translateY(10px); }
    to   { opacity: 1; transform: translateY(0); }
}

.activity-card { transition: all 0.3s ease; cursor: pointer; }
.activity-card:hover { transform: translateY(-5px); }
.activity-filter-btn { border: none; outline: none; cursor: pointer; transition: all 0.3s ease; }
.activity-filter-btn.active { border: 1px solid var(--theme-primary); box-shadow: 0 0 10px var(--theme-primary); }
.activity-list-grid { max-height: calc(100vh - 250px); overflow-y: auto; padding: 10px; }

@keyframes pulse-glow {
    0%, 100% { box-shadow: 0 0 5px var(--theme-primary), 0 0 10px var(--theme-primary); }
    50%       { box-shadow: 0 0 20px var(--theme-primary), 0 0 40px var(--theme-primary); }
}