I know this is probably a small learning project, but I'll just give some feedback on what I would think about for if you wanted to make this into something proper (and, I think a learning project can still have cool design!) Obviously this is just how I view games you can disagree etc. blah blah
- I think a good action game "start" immediately. Not just in terms of how long it takes from opening the game to actually playing, but also in terms of how long it takes to ramp up and get interesting. The game starts with you just planting stuff and it also takes a few waves for enemies to show up. I like hard games so I think it's good if I'm fighting for my life from frame 0 but in any case I'd still make it much harder from the get go. Also consider if I have a high score of like 50 waves survived and I'd like to try beat it again. Would I really want to sit through 30 easy waves before the game becomes interesting again, just to try beat my score?
- The player movement has inertia i.e you have to accelerate up to max speed instead of just moving at that speed immediately. This isn't necessarily bad, but I'd be very careful of this mechanic in action games, especially ones about avoidance. Your character movement can still "feel" smooth, even if they instantly move at max speed if you just animate the character nicely. Then you have much more control over your character and you have more room to work with regarding making the game more difficult.
- The enemies are way too slow and you can just walk around them in circles.
- This is compounded with how the play area is wayyyy too big. You have so much space to dodge stuff, so it's really hard to constrain the player in any way. I think you should try tip the scales in favour of the enemies, and have player constantly trying to claw their way to victory. This way, the game is constantly challenging and engaging.
- You can plant and harvest the crops from way too far away, so you can safely collect and plant them without risking the enemies destroying them.
- I like how the game doesn't pause while you use the shop. I do mind how out of the way it is though.
I think avoiding enemies while trying to plant your stuff is actually a pretty cool concept if you took it further, but it'll work a lot better if it's more constrained. (If I were to make something like that, I would probably make it a pure avoidance game and remove the ability to just shoot the enemies. A creative way to kill them could be cool though)
(I wrote all this not cause I think you suck or something, but cause I know putting something online and having very few people see it is very discouraging. I know when I put something out I'd like people to take the time to give their thoughts on what I made. Good luck with your future games :D )