Really nicely implemented mechanics, that does a very good job of being gameboy-like, more so than just having 4 colours/a limited resolution.
I liked that it told me nothing about the world - it was all just there for me to work out and the mechanics all emerge quite easily.
The AI was more cunning than I expected, always avoiding your line-of-sight until it was forced to step into your path.
Oh, and just so you know, you can exploit the travel time on the cannons shots to jump out of the explosion radius, even if you shouldn't have been able to from the regular timings. Also, any time I reloaded without enemies present I'd fire off a round without pushing "fire" again.
Incredible game with a challenging final level - feels good to have overcome it and reached the end.