I think Entry01 is too difficult, mostly due to it's lack of context. Test chambers within Portal & Portal 2 follow a similar format: Chamber 1: Teach a player a new mechanic, Chamber 2: Give them an example of how to use the mechanic, to get them thinking about it for the next chamber and Chamber 3: Stick them puzzling situation utilising the stuff they know about. My feedback would be to try and follow the format Portal & Portal: each chamber should have an objective to achieve - something to teach the player. Also, check out the Summer Mapping Initiative contest thinkingwithportals.com are running: http://contest.thinkingwithportals.com/