I wasn't able to get far in the game. Any time I'd purchase a tower that harvests gems, it would shrink and disappear - repaying less resources than I'd used to buy the tower. I didn't have enough gold to buy enough towers to get any further than Wave 4. I think it's necessary to either re-balance the game, or demonstrate how to play the game correctly.
Assuming your team's made the art, it's a nice looking set of sprites. But the Unity engine work (like UI) and a lack of sounds needs some polish.