Nice little game. Unfortunately, with only one object you need to hit and no physics beyond the catapult it lacks the strategic depth that similar games such as Angry Birds have. The concept and art are really cute. I don't know how many times I killed the cow before I managed to hit the UFO lol
I don't know if that wouldn't be against the rules of the original jam you made this game for, but you could make the main gameplay loop 20 seconds and then try to turn it into some kind of roguelike or a something like that, where each "level" or wave would last 20 seconds and then you could buy some stuff for example. That would give the game another layer of strategic depth, and would make it even more replayable.
Also: did you make the art for the thumbnail and the game yourself or did you use AI? AFAIK AI art isn't allowed in this particular game jam. I'm asking because it has that light yellow tint which AI sometimes adds, but it could also be just normal non-AI art