Very impressed to see some interesting puzzle mechanics in a sidescrolling shooter! The cutting and gravity puzzles sure added a lot to the game, and the level designs were amazing and clever. Almost every level introduced a new enemy or obstacle, so things were always interesting.
The advanced physics made it fun to play around with stuff, though also lead to a few bugs... but overall they weren't frequent enough to ruin the game for me.
The game presentation was great; the graphics, music and plot are all simple yet appealing and polished.
However, as many people have mentioned, the difficulty was a bit cheap. Most often I was killed by the scrolling screen. This is especially frustrating when you have to figure out a new puzzle or remove a wall, and you're really forced to play through trial and error, and memorize what's up ahead. That's bad game design, especially for a Flash game. Either a more forgiving scroll speed or some checkpoints would really help out and make death less frustrating. Or you know, you could add an easy mode.
A bigger screen resolution would be nice too. I noticed that stuff that's off-screen behaves normally, which is annoying when enemies shoot projectiles back onto the screen.
Another huge problem is that there's a lack of collectables and upgrades. People love those. They add replayablity and mean that even if you keep dying, it's not so bad if you can retry with new upgrades. HP and attack improvements wouldn't even be hard to implement, and having some other items to collect would make the score system more fun.
So overall, the game mechanics and presentation were awesome, but the pace of the game could really be improved by reducing the difficulty or adding some collectables.
I'm hoping to see a sequel with that stuff fixed!