I'm going to be honest. It's terrible. It's incredibly old, though, so I'll give it SOME slack. Having the spacebar as jump isn't so bad, I've seen worse, though it would have been better if jump had been the up button.
My problem, though, with this game is that jumping is just god awful. Going up is alright. That's not too bad. But you drop like a rock and there's no time to react. You stop moving when you reach the top if you're trying to run and jump, so there's no momentum at all. Trying to reach the other platforms is a chore, and I find myself focusing more on getting to a single platform where most of the items are appearing than running around gathering the other items.
I gave you half a star because it's old and I understand that 2005 was a very difficult time to make games like this. Had this been any newer, it would have received a solid 0.