Passage is essentially a depiction of life and the design has some very interesting implications. Early on you can meet the love of your life, but if you go exploring you can miss her and go through life without her. More amazingly you can go straight from beginning to end in a straight line if you never move down on the screen, just running through life as fast as you can. About halfway through the fact that you, and you lover if you found her, is obvious enough that you can't miss it anymore. It also becomes clear is that the characters position on the screen is moving steadily to the right, which gives a sense for the approaching end of life, even though you didn't notice it in the earlier part of the game. There's some very deep depictions of life in these design decisions.
The most shocking part of the game was when my lover died. It happens sudden and unexpectedly, and moving backwards won't bring her back, just as once you move to the right and age you stay that age even if you try to return to younger years. Furthermore, I had noticed that my lover had actually impeded my progress through the game because she increases the amount of space between the walls of the game that is required for both of you to slip through as you travel through life. Her presence also makes certain chests (which either sprout black dots that don't do anything for you or stars that add to your meaningless "score") unreachable. At first I was upset that the designer would depict love as such a hinderance, but a second thought made me consider if it was actually worse to have a lover to keep you from racing through life? Is a success that means nothing in the context of death worth more than love?
After my lover died I was more than a little bummed out by it, and I will admit I raced to the right as fast as I could to meet my own end, which wasn't as fast as previously because I could no longer walk as fast as I used to. Then I died, and it was over.