Try Expanding it a bit

The game is only really interesting for the first ...half a minute. You could definatley make this into a better game by using what you have here as "framework". Try adding some difficulty levels, and working on making the Special Effects (basically the animation that shows when you whack a plant) look better. Maybe add abilities that you can unlock with some sort of currency system, abilities such as slow down etc. that work toward's the player's advantage.

this is very good

but it would be better if the plants didnt stay up for .5 seconds, give it a 1-2 second time so we can actually see and click the piranha plant.

Whack A Planet

This game looks pretty good. I like the retro feel. The music is cool and it flows ok. But it took me a while to actually figure out what the point of this is. I don't mean to sound rude about it at all. I just think maybe clear instructions on how everything works. Also a different scoring system would probably be an advantage aswell.

unfortunately

i found it to be boring. a few things you dound work on is maybe making a betting score system based on timing anf make them all the same size. these will most likely help you.