Lovely polish, with the wipe for the switch (though the music restarting was a little odd) and the explosions on hitting the asteroids.
I thought it was a little easy though - I survived for at least a minute staying still in the middle and switching once every few seconds. Might be cool to have white asteroids produce black ones on destruction and vice versa, so that the two states are a bit more linked.
Overall, very impressive for a three hour project, nice one!