The game does not have a properly challenge, and that makes it boring. But i see you intend to keep improving this. The low-poly desing is very well done, my suggestion is to place a seed counter, in order to make easier to the player know when he can and cannot drop seeds.

I didn't understand the controls for the tank at all. At first I thought they were "tank controls" but they were not.

I like the idea of your game. The controls definitely need revising, and adding sound would add to the atmosphere. If you can add the ability to fire on the enemy tank to either destroy, disable, or slow down that would make the game more fun. Also adding more random seeds will make the gameplay more fair and enjoyable. Continue working on the project and turn it into a fun and exciting mini game. Well Done!