Not too bad.
I like how you made something different from most similar games, with the combining of materials to produce defenses.
The user interface doesn't feel all too intuitive at first. I feel like you could have taught the player one thing at a time, starting with constantly producing the first three basic materials. Then teaching them to use the shop, etc. On my first play, I didn't realize I could produce basic materials, so I didn't get very far, and didn't really understand what I was supposed to do.
The materials and combinations could have been a bit more imaginative, but that is something you can possibly improve on in future games.
I also think it feels a bit unfair how everything is easy for a long time, and then suddenly a hoard of enemies appear and rush you. The difficulty could increase gradually. It's good to have bigger groups appear sometimes, but the way it is they kind of catch you by a surprise game over. I would have played longer, if I hadn't gotten a game over so suddenly...
The graphics look okay, I'm glad you drew the units as animals with detail.
Overall, this game has the feel that it's well made, but still lacking in many ways and it doesn't entertain you for very long.