Hi! Thanks for your feedback! :-)
Yeah, the game is definetely super unbalanced. Things came up on the last days and I had little time for the game. I think I ended up having like less than an hour for balance.
There was a fourth plant (that I had to cut off due to lack of time) that allowed you to have some control over enemy spawn. I agree having an enemy spawn right next to a plant feels cheap. You can move to agro them far from the plant but that strategy only works on some cases.
The yellow squares are just the enemy trail. I added them when enemies just teleported from one tile to other so you could see where they came from. I guess now that the enemies move properly those yellow are distracting and confusing.
Again, thanks for the detailed comment!