float PI=3.1415926;

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = fragCoord/iResolution.xy;
	uv = uv - vec2(0.3f,0.3f);
    // Time varying pixel color
    vec3 col;
    float angle = -PI/4.0f + float(iFrame)/10.0f;
    vec2 rot;
    rot.x = uv.x * cos(angle) - uv.y * sin(angle);
    rot.y = uv.x * sin(angle) + uv.y * cos(angle);

    col.x = sqrt(rot.y);

    // Output to screen
    fragColor = vec4(col,1.0);
}