Hi hungertod,
thank you for your positive feedback and playing!
I will tweak the jump functionality for a better feeling. I think it can be better :-)
Here is a hint to find the key in level 2 if you want to retry.
WARNING SPOILER:
The last elevating platform, before you can get to the Computer, goes further up to another path on the left. You can find the key on the end of this path.