I agree with the previous reviews - this is a great game but suffers tremendously from things that are very easy to tweak:
1. for horizontal movement, check for either A or left arrow, and for either D or right arrow, being pressed so players can use whichever they want.
2. jump with W or up arrow
3. interact with space or down arrow
4. helicopter with the same button as interact if there's nothing there to interact with
5. don't end the game if you reach the top before finding everything (or at least allow the previous progress to be continued if the player resumes afterward)
That should make it more enjoyable for most people, and the rest of the issues (aside from reports of lag) should be minor. I haven't encountered the lag that some people have, so can't really comment on it. It is a good enough game that I'm replaying it after having it end sooner than I wanted it to, even though it means I'll need to redo everything.