#ifdef GL_ES
precision mediump float;
#endif

uniform sampler2D u_texture;
varying vec2 fragmentTexCoord;

void main() {
    float dir;
    vec2 coords;
    float offset;
    float pixelDistanceX;
    float pixelDistanceY;

    pixelDistanceX = distance(fragmentTexCoord.x, 0.5);
    pixelDistanceY = distance(fragmentTexCoord.y, 0.5);

    offset = (pixelDistanceX * 0.1) * pixelDistanceY;

    if (fragmentTexCoord.y <= 0.5) {
        dir = 1.0;
    } else {
        dir = -1.0;
    }

    coords = vec2(fragmentTexCoord.x, fragmentTexCoord.y + pixelDistanceX * (offset * 8.0 * dir));

    gl_FragColor = vec4(texture2D(u_texture, coords).rgb, 1.0);
}