Thank you Alexandre for the feedback!
The UI has always been a problem in my previous games, I posticipate it and then there is no time to add a new HUD. For the earthquake effect, I think you mean the spawned rocks, because when you kill an enemy the rock spawned follows the enemy, yes. The collisions are very time consuming and is something that I would sacrifice, I think that does not change so much in the experience of a small prototype :) Same for the pause/exit option.