I really enjoyed the simple, yet elegant art style and the overall game play mechanics.
The only thing that hurt the experience for me was the extremely short time limits in some levels. At first I had no idea why I was randomly dying in the third level until I noticed that it only gave you 7 seconds to complete it. Now don't get me wrong, I love challenges that have constrained time limits, but I feel like the difficulty curve could have been a little more forgiving in the earlier levels, especially when the main mechanic involves searching for hidden enemies.
Other than that, I still enjoyed the game overall. Great work!