I want to like this game, but the difficulty level is way too high! It took me several tries to get past the first waves.
Main concerns:
- There is so little time between waves to build and farm
- Buildings are too expensive
- Food requests are overwhelming
I would suggest adding more time between waves, and restricting food orders to a few common types in 2-5 piece batches of plants for the first few levels, then adding in more exotic and larger ones later.