...and now I'm stuck again, but not in the "error in the system" way, just in a "what am I supposed to do from here" way. I've got four arrow keys and the space bar, but there's a block in the air that I can't move down far enough to reach; and getting back to the start requires giving up the up-arrow to take the elevator-block, but then needs an up-arrow to get past the walls.
(Also I put the spacebar in Experiment 3 and got...a mini-sunglasses guy, but no controls.)