使用 Three.js 实现电磁场效果，具体要求：

【核心特效】
- 径向电场线
- 环形磁场线
- 正负电荷效果

【场景与光照】
- 纯黑色背景
- 自发光效果
- 闪烁动画

【交互与控制】
- OrbitControls 视角控制
- GUI 参数调节面板
- 重置功能按钮

【技术要求】
- Three.js 最新版本
- lil-gui 控制面板

float electricFieldLines(vec2 uv, float time) {
    vec2 center = vec2(0.5, 0.5);
    vec2 dir = uv - center;
    float angle = atan(dir.y, dir.x);
    float dist = length(dir);
    
    float radialLines = sin(angle * lineDensity + time * pulseSpeed) * 0.5 + 0.5;
    radialLines *= smoothstep(0.0, 0.4, dist) * (1.0 - smoothstep(0.4, 0.8, dist));
    
    return radialLines;
}

float magneticFieldRings(vec2 uv, float time) {
    vec2 center = vec2(0.5, 0.5);
    float dist = length(uv - center);
    
    float rings = 0.0;
    for (int i = 0; i < 3; i++) {
        float radius = 0.1 + float(i) * 0.15;
        float ring = smoothstep(radius - 0.02, radius, dist) * 
                   (1.0 - smoothstep(radius, radius + 0.02, dist));
        
        float pulse = sin(time * pulseSpeed + float(i) * 2.0) * 0.5 + 0.5;
        rings += ring * pulse;
    }
    
    return rings;
}

float chargeEffect(vec2 uv, float time) {
    vec2 positiveCharge = vec2(0.3, 0.5);
    vec2 negativeCharge = vec2(0.7, 0.5);
    
    float positiveDist = length(uv - positiveCharge);
    float negativeDist = length(uv - negativeCharge);
    
    float positiveField = smoothstep(0.1, 0.0, positiveDist);
    float negativeField = smoothstep(0.1, 0.0, negativeDist);
    
    return (positiveField - negativeField) * 0.5 + 0.5;
}

float flicker = sin(time * 10.0) * 0.1 + 0.9;
color *= flicker;