Pretty 'n' fun. Though if I'd fallen down that pit after getting out again I may have destroyed all humans. Making it escapable with the umbrella would have gone some way to ensure I didn't blow up the planet.
It's a small thing, though, and would only affect me if I'd been clumsy (it happens to us all occasionally).
The jumps were not quite frustrating though it was a fine line at times. I had some good 'aha' moments, like in the screen with the umbrella, where I realised things weren't as impassible as they initially appeared. I really liked how you displayed the pop-out-spikes and unclimbable walls before they became dangerous - that was really well done, so... well done!
Intro and outro were basically pants, though.
Still, 'twas fun. You did a really good job of teaching the players the internal rules, the difficulty was constant and well balanced and the atmosphere was great (apart from the intro and outro, which were mood-killers).