Nice game! Interesting mix, i liked it alot. You should add more sound effects (when the monsters die, maybe a little battle soundtrack going in the back), but overall, nice sounds!
The graphics are nice, i like how there is a mix between 2D monsters and 3D background.
The gameplay is easy to figure out, but maybe you need to add a tutorial to let people know when exactly to press keys.
Overall, a very nice and unique game, i liked it alot. Keep up the good work!