Impressive but could be better designed
This really impressed me - I mean, it's a large environment and - whilst slightly flawed (your method of having platforms stop a descent makes for bouncing at all times and collected items flash up briefly when revisiting a screen) - the engine does seem really well built.
The graphics are really nice, and the sound - whilst annoying after a while - is good too. I'd have rather there was a 'music off' button tho'.
The controls worked well and the front-end was nice enough.
However, I just felt the general design could have been a lot better.
When I started, I didn't realise the collection of cheese and stars was the whole point of the game - I collected them, but concentrated on getting to the end. It was only then that I realised I'd basically have to go through the game again, this time making sure to collect each item. If I'd known from the start, that would have saved a fair bit of frustration.
Also annoying is the falling, general re-treading of paths already trod and the fact that I fell a couple of times into the first screen, wherupon the checkpoints seemed to be reset and I started again from the mouse hole.
The level design seems nice enough (definitely as good as Asterix on the SNES anyway) but there's nothing that seems genuinely inventive, no surprises but a couple of sections that seem slightly flawed in their design. (Much like the aforementioned Snes game.)
Still, I'm comparing you to a professionally-made game and so I hope you take that as the compliment it is.
I just felt that this wasn't nearly as enjoyable as it could have been had even more thought been put into the design.