Thanks for the feedback, and I feel you about the lags!
If I can bring some technical details, the way how coly currently find the enemies is by only doing a very primitive operation: get all unit on the arena; iterate each of them and check whether it is an enemy; search the closest enemies among them all. I think this logic is being run eagerly without any defer behavior, and this is my first guess of why the game lags/crash when many unit is being spawned, as each individual would do this on every scan state. I Plan to fix this some time later after I got more feedback from this event <3