Just tried out this game and I see great potential, but like most small pvz fangame reviews I make, I'll tell u the things that would be very nice in the game
1. add music and sound effects
2. add cherry bomb
3. add more zombies
4. add the shovel (of all the ones so far, this is the most important)
5. add UIs like the wave system, and the wave progress bar
6. add a main menu, and maybe a level select menu
7. add more difficulty (increase the spawn rate)