This has all the makings of a really good "tough-as-nails" platformer. Plus the whole concept of having a time-limit be a natural part of the story is perfect. I do think the penalty for failure is a bit steep, but I also know checkpoints are probably not easy to put into a game like this. The difficulty curve starting out is pretty high, but you do get used to it quickly. Once I got the hang of it, it was a lot of fun and very addicting. Good work
(edit) Bravo on the idea. I thought it was brilliant!