Models and animations look good. I would only complain that targets look similar to background elements.
Stealth mechanic is intuitive, but I'm not sure how to feel about that enemies are able to see me through walls.
I would complain about too slow speed on vertical directions. At least faster descent or fly mode canceling would be nice, but otherwise after a few tries I could learn how to move faster. Tutorial helped that flying is under W not Space.
I didn't notice description of the game and I thought at first that UI showing hive alert showed thing good for me.
There are a few bugs:
After finishing tutorial I couldn't use stealth ability.
After reloading page I could sting everything without limits.
Until I was moved on Z axis and I couldn't attack targets.
High reward targets were harder to get as promised.
It was cool that some enemies walked in circles around protected targets instead just walking right and left.