Random GLSL thing

#ifdef GL_ES
precision mediump float;
#endif

#define PROCESSING_COLOR_SHADER

uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;
uniform sampler2D test;


void main() {
//    vec2 st = u_mouse/u_resolution;
    vec2 st = gl_FragCoord.xy/u_resolution;
    st.x=(st.x-0.5)*u_resolution.x/256.0+0.5;
    st.y=(st.y-0.5)*u_resolution.y/256.0;
    vec2 gg = vec2(1)-vec2(u_mouse.x,u_mouse.y)/256.0;
//    float pos=mod((   st.x+((st.x-0.5)*2.0*(atan(abs(st.y*st.y*st.y*2.0))/-3.14*1.0+1.0))   )+gg.x,1.0);
    float pos=mod((   st.x+((st.x-0.5)*2.0*max(1.0-(st.y*st.y),0.0))   )+gg.x,1.0);
    float wow=sin(pos*3.14*16.0-3.14/2.0)*0.5+0.5;
  vec3 col = texture2D (test, vec2(pos,mod(st.y,1.0))).xyz;
    gl_FragColor = vec4(vec3(pos),1.0);
}