precision mediump float;

varying vec2 vTextureCoord;

uniform float invert;
uniform sampler2D uSampler;

void main(void)
{
    gl_FragColor = texture2D(uSampler, vTextureCoord);

    gl_FragColor.rgb = mix( (vec3(1)-gl_FragColor.rgb) * gl_FragColor.a, gl_FragColor.rgb, 1.0 - invert);
}