This is a nice idea, whcih could use a few alterations.
The UI could be larger and clearer, with some flash or sound or colour change to make it more obvious to new players what the controls currently are and make it more obvious that this is a game where controls change.
On the subject of the controls, I would personally advice that this game shouldlimit contorls only to the spacebar and the letters. Other keys have the trouble of not appearing on some keyboards, appearing in diffferent places between countries and of peforming other important tasks (such as esc, for example)> I had noticed that a few of the controls wouldn't work on my PC and expect this is the reason. (Also, one of the controls was sometimes just a gap? This didn't seem to be spacebar, so I wonder if it is a key I'm unaware of or if that action was just turned off for that period as partof the game?)
Here's some feedback that I keep recieving that could apply here aswell, add sound controls. This loks like it might be one of your first games, so perhaps you simply haven't learnt how to add menus and such (I've only just begun to add such things recently). It isn't vital, but it will make your future games more approachable if you spend some time on it.
I thought this game was clever and enjoyable and I'm sure there's a million things you could do to take this idea further. Well done. :)