On design: Very Good.
The blunt humour of the signs and the usage of tilesets was very good. However perhaps you would have done better if you had preserved that nearly monochrome minimalistic look all the way through I may have been more satisfied.
In terms of originality... I can't say you have copied a style without saying that you have copied a style somewhat new and still rare, so I wont say anything on the matter.
On gameplay: Very Good.
You do know how to make a difficult level without putting 17 sandcrocs on every layer. However this can't be said about ROOM 27 :3
I am at loss, truly brilliant challenges, albeit near impossible for me.