Definitely a good concept and something fresh!
I think the challenge mode may start off a bit too difficult (or I just suck awful, which is likely) and maybe should have more of a steady ramp up in challenge.
For targeting the flowers I would say if your current system is tuned for difficulty then stick with it, otherwise I think I would prefer to control it with A & D (ie left and right respectively), even just keeping what you have and adding it so you could toggle with that as well would be nice.
Those are the only two gameplay things that really come to mind for me, otherwise it was awesome.








