Holy crap, so many comments!
@JaJ, @Jezzamon - yeah, I'm adding that in to go in a new version (which will pretty only add text like that to give a little more guidance) - should be up in the next day
Also @Jezzamon - would you have preferred a keyboard input?
@racarte - The metaphor was admittedly less clear than I'd like. The world actually represents the characters' 'tiny world' - the space they've created for their relationship. The balls represented outside influences: red ones being those that they wanted to keep out, and green ones being ones they wanted. The idea is that the lovers start out by secluding themselves from the world, then as they start learning each others quirks and annoyances, they begin to grasp at outside things to distract them. For the relationship to survive, they have to strike a balance. I was hoping to show this through the visuals, but simply didn't have time. (I'm gonna be recording a commentary for the game soon that'll go through this in more detail)
@Super Soul - Yeah, that would have definitely made the differences between the win and lose states more clear (I'm suddenly having a thought of a musical with a clear hero and villain, and how much air time they get determines who wins!). It would have been hard to pull off with the particular story I was telling, unless the goal was to balance out the voices rather than to have one of them dominate. Another way I was thinking of was to have the music itself change with winning and losing (though that would have been far too much to compose in the time allotted).