I can't help you with the solution 'cause I don't have the game at hand to play, at the moment. Though, I would like to prepare you a bit, if you have intended on playing the game through: if you beat the game could you take note on wether or not you get the 'Happy Ending' or 'Bad Ending'?
A friend of mine played through the game and the ending was anything but a 'happy ending'. They were more or less sure that they had done something wrong to recieve this 'bad ending'. I can't play it through (I am not even sure I would manage the later levels if I would have the game at hand), but it would be interesting to see if there is an alternative ending to be found.
Thanks in advance, and good luck on beating the game if that is what you intend on doing! Heck, it is hard, is it not? ;-D