One of the many!
Although there's a huge lot of this type games, yours is kinda outstanding, as it comes with a nice variety of levels and neat twists to the original gameplay.
The only problem is, that you challenged us with the 'you can't cheat'. If you say something like that, first make sure that it's true. I'll suggest that you disable mouseclicking after clicking on 'start'. The finish will be reached by touching it, or something. It's an easy change, but it'll eliminate the most commonly known mouse - game cheat. Just preventing the users to tab doesn't solve anything. But hey: Even the tab - cheat works, somehow.
I'm a cheat whore, so I couldn't do anything about it: I HAD to cheat. So please, upload a cheatfixed version, just for me, will ya? :-(
5/5