Oh yeah, I didn't get around to updating the description yet. But you can increase the amount of ducks that get put on the conveyor belt in the control room. We didn't get around to setting proper difficulty presets, but some stuff is configurable ingame to offer a bigger challenge.
There is also three conveyor belts to active, not just two. There was the idea to have them activate/deactivate randomly, but no time to implement it either.