void main() {
    vec2 p = (gl_FragCoord.xy - 0.5 * u_resolution) / min(u_resolution.x, u_resolution.y);
    float t = u_time;

    vec3 bg = vec3(0.012, 0.008, 0.030);

    vec2 c1 = vec2(-0.22, -0.18) + 0.020 * vec2(sin(t*0.13), cos(t*0.17));
    vec2 c2 = vec2(0.28, 0.25)  + 0.015 * vec2(cos(t*0.11), sin(t*0.19));
    vec2 c3 = vec2(-0.12, 0.38) + 0.025 * vec2(sin(t*0.09+1.0), cos(t*0.14));
    vec2 c4 = vec2(0.38, -0.32) + 0.018 * vec2(cos(t*0.15), sin(t*0.10+2.0));
    vec2 c5 = vec2(0.02, -0.42) + 0.022 * vec2(sin(t*0.12+3.0), cos(t*0.08));
    vec2 c6 = vec2(-0.40, 0.02) + 0.016 * vec2(cos(t*0.16+1.5), sin(t*0.11));

    float r1 = 14.0 + 6.0 * sin(t * 0.70);
    float r2 = 12.0 + 8.0 * sin(t * 0.90 + 2.0);
    float r3 = 16.0 + 5.0 * sin(t * 0.60 + 4.0);
    float r4 = 11.0 + 7.0 * sin(t * 1.10 + 0.5);
    float r5 = 18.0 + 4.0 * sin(t * 0.50 + 3.0);
    float r6 = 15.0 + 6.0 * sin(t * 0.80 + 5.5);

    float d1 = length(p - c1);
    float d2 = length(p - c2);
    float d3 = length(p - c3);
    float d4 = length(p - c4);
    float d5 = length(p - c5);
    float d6 = length(p - c6);

    float i1 = exp(-d1*d1*r1) + 0.35 * exp(-d1 * r1 * 0.28);
    float i2 = exp(-d2*d2*r2) + 0.35 * exp(-d2 * r2 * 0.28);
    float i3 = exp(-d3*d3*r3) + 0.35 * exp(-d3 * r3 * 0.28);
    float i4 = exp(-d4*d4*r4) + 0.35 * exp(-d4 * r4 * 0.28);
    float i5 = exp(-d5*d5*r5) + 0.35 * exp(-d5 * r5 * 0.28);
    float i6 = exp(-d6*d6*r6) + 0.35 * exp(-d6 * r6 * 0.28);

    float field = i1 + i2 + i3 + i4