Thanks for playing. The repulsor is tuned so that you can only reliably hit the enemy when closing distance, which is meant to discourage kiting an entire fleet of enemies around the map and instead being a bit more aggressive. But I didn't put too much thought into balance, it is meant to be challenging since it's a very short level.
The pixeljitter issue I've noticed too, and is one reason the star background doesn't move because if it does it's the pixels become very obvious, I will investigate solutions, thanks for the link