The most fun I'v had with Pico
The game play is simple, but very refined and fun to play. Dodging around enemy attacks, and blasting away at them is easy and exciting, especially when there is more than one coming after you. The art and style of the game is also very appealing, and the animations were smooth.
The levels are pretty cut and paste, but you did a good job of keeping things fresh with lots of interesting enemies, and a little donkey-kong-esque mine cart ride near the end.
The final boss was a bit of a let down, but the ending was appropriate and satisfying.
Overall, I loved it, and there was enough to make me go back and try to unlock the achievements. Some power ups for Pico's weapon or maybe some branching paths in the levels would have been really cool, but the stuff you guys put into this game is polished to a mirror shine.