Ooh, an after-image trail would be really cool, great idea!
That the cursor is also affected, when the game is not in focus should definiteley adressed, should I expand this game.
Maybe giving more clues to keep the players playing until they've seen the control twist and the enemies might be a good idea, however I haven't had one person say that they don't get how the game fits the theme. As far as I know all players at least played until the enemies occured.
Then again, maybe the others simply didn't comment.
I thought that that might be a problem and so I at least minimized the time until the control change.
Thank you very much for playing and for you detailed feedback :)