Thanks for the feedback! I must admit it myself that a big problem with my game is lack of instructions. I did not focus on it early on, so when the deadline approached I quickly wrote a "READ ME" text where the instructions were hidden.
The difficult to get key was intentional to pro-long the play time a little bit and make it a little bit harder. You need to press space while you are on the key and the catch is that you can't see the player falling on the key, so a little bit of a guess work (frustrated even myself). But if it's true that you didn't get past the key part then I still recommend you to see the ending (it's not very long).