This is probably my favorite original piece since Tick Tock ヽ(･∀･)ﾉ Its theme is post-apocalyptic, and has incredibly vague lyrics on how I'd write a song. It's more like, "Here's how I used to write music, before the world ended. All I'm left with now is a Toy Piano."
It'd be impossible to compose the many parts of a song with a single toy piano. There'd be many unwritten melodies that would haunt me, and I would never be able to play them for you.