I love some plants vs zombies.
There was some scaling and UI issues with fullscreen on my ultra wide. I bring it up because even on normal aspect ratios, different resolutions might render things different than what you expect. I suggest stretching your gameplay window to weird sizes/shapes to make sure UI looks good no matter what.
The one-hit kills seemed a bit much and missed an opportunity for strategy. Ie if it took longer for an enemy to kill and ice cream tree vs a shooter, it'd incentivize putting trees in front of the shooters to act as shields, when novice players would instinctively do the opposite.
All around more visual feedback would be good. Ie grey out a unit if you don't have the money to buy it, show a transparent version on the tile before placing, stuff like that.
This is the UI issues I was mentioning. The unit tiles are far from the gameboard, likely because they're anchored to the edge of the screen and was expecting a more normal resolution. The text is a bit small, not sure if that was intentional or if you tested on a lower-res setting.