#4

// Author: Maximilien "cewein" nowak
// Title: moving 2d metaball

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;

#define ZOOM 1./0.596

vec3 makeSphere(float size, vec2 pos, vec3 color, in vec2 st)
{
    float pct = (distance(st,pos) * distance(st,pos+-0.792))/abs(0.5);
    pct = smoothstep(size,size-0.03,pct);
    return vec3(pct * vec3(color));;
}

void main() {
    vec2 st = gl_FragCoord.xy/u_resolution.xy;
    st += vec2(-0.450,-0.420);
    st *= ZOOM;
    vec3 color = vec3(0.0);

    color = makeSphere(0.5+clamp(0.,0.175,abs(sin(u_time)/3.)),vec2(0.570,0.370),vec3(1.,0,0.),st);
    color += makeSphere(0.764-clamp(0.5,0.0,abs(cos(u_time)/3.)),vec2(0.390,0.640),vec3(0,1,0),st);
    color += makeSphere(0.356,vec2(0.660,0.680),vec3(0,0,1),st);
    gl_FragColor = vec4(color,1.0);
}