A nice effort.
The fact that you can freeze your character to a platform is a very decent idea, and i've never seen anything like that in a platform game before. It's fun to create your 'own' platforms to finish the level, so well done on that!
On to the rest of the game, the controls are just a tiny bit unlogic for me. I think not many people are used to use Z to jump for example, so for example the space bar would have been better. It doesn't really matter as it's easy enough though. But still, very simple controls and lots of fun!
I really like the style you're going for, considering this looks like an old game with 8-bit music. Who says that can't be fun? It's simple, but cool.
I think you could have added some additional stuff. As i played it, it's only grabbing a key and going to a chest. Fun enough, but if you invented stuff like items or enemies, which i didn't see in this game, it would have been even more challenging! Also, the levels get more difficult quite fast. It would have been nice if you added more backgrounds / level styles, just makes the game more interesting in my opinion. Maybe you should have added one or two more music tracks, as there's only one in this game.
Over all this a very nice game which works even a bit addicting. A really nice effort. But you can make it more fun / challening. I'd like to see more of your work. Keep it up!