It is about humankind's relationship with time. I think a lot about time, generally, as a character of mine (who might or might not appear in a later version of the game; and, no, I'm not talking about Great Grandfather itself), as an ally to work with or a foe to race against. To some extent, I think everyone shares my fixation. Time's a given, an unbiased, neutral facet of our universe, but oftentimes we view time as an antagonist because of what it means, what it measures. In any case, its presence is something we all have to come to terms with.
As time's too big a concept to tackle as one unitary thing, this will eventually be split up into two or three parts: past, present, and future. Each will likely be an entirely different story launching off from the same location.
Right now, only the 'past' path is complete (and certainly requires further expansion). I tried to get across how much time we waste and how much pain we cause ourselves by reliving past memories; focusing on yesterday's failures keeps you from living in today. Sure, regret's a painful thing. Nostalgia can make the present painful, too. But focusing on things you've done will keep you from doing anything else. You can reach one of two endings, based on your choices.
I should probably say that I'm taking memories and the past as different sides of the same coin here. They're not exactly so- because the past is a definite, solid thing, and memory's too unreliable to have a solid shape; it exists in more of a fluid state. As I learn more intricate Twine coding, I will incorporate that idea into the game itself....There are so many dimensions to our relationships with the past that it's hard to get everything down into one story route. I'll be expanding on this periodically, from different angles, working outward. Hope I can get my own writing pattern down to clockwork. I'll get there one of these days.
I hope you enjoy the game.