I really needed some documentation for the programming language. It took me forever to figure out the gravity thing, which was arguably the easiest problem, haha.
The game is very clean and nice-looking! I enjoyed the experience as well, and the hacker's text were quite amusing. The out-of-the-box solutions to the challenges were very cool. Had fun figuring them out to some extent, enough so that I kind of wish I turned off the notes.exe bit.
I don't know if it's just me, but the cursor didn't always show in the Code.exe window, particularly when you're on a line with no code, which made it a bit difficult to see where I was before typing. (But it's a minor inconvenience.)
I would have liked some music (maybe a musicplayer.exe app that could be used for something else in the puzzles as well?).
Overall, really good. I liked it a lot.