//!HOOK MAIN
//!BIND HOOKED
//!DESC Obvious test shader: invert + red tint

vec4 hook() {
    vec4 c = HOOKED_tex(HOOKED_pos);
    c.rgb = 1.0 - c.rgb;      // invert colors
    c.r = min(c.r + 0.35, 1.0); // extra red tint so it's unmistakable
    return c;
}