The levels aren't really re-playable, which might help with retention. For example, games like Angry Birds, Cut The Rope and others were sticky because they had more than just the linear path from start to finish; you could improve your score by trying levels repeatedly until you attained a 'perfect' score.
My new game (Paladin's Passage) had the same problem initially: once you completed a level, the only reason to go back would be to get a better time, which wasn't really incentivized. I completely revamped the level progression, eliminated the idea of lives, letting players replay levels as often as they wanted, and put non-linear goals (partially-hidden collectible 'secrets') in each level to incentivize replay to try to get a perfect score.
I agree with some of the other comments as well; the controls are still a bit janky. It is tough to get 'flow' going. Also definitely needs some sounds: music, environmental, etc.! Even a placeholder of something royalty-free would be an improvement.