-Create a random active object.
-Make it have a short path movement (around 32 pixels, make it that big too), make it loop and reverse at end.
-Make the object stop at the start of the level.
-When the backspace button repeatly is pressed, the object speed is 50.
-When the any key is pressed AND the object is stopped, then your action will happen.
Or you could:
-When repeated NOT pressing backspace AND pressing the any key.