Thanks for playing and for the great feedback! The muddy-looking splotches on the background parallax layer are from the texture being blown up. I'm afraid there is not much I can do about that without manually erasing them all, which would take a while. Thank you for pointing it out tho, though I might take the time to do that in the future.
As for the theme, I went with "the death of a planet" being the beginning of the game. The game is set in the debris field surrounding the collision of two planets, as briefly described in the intro sequence. After all, the mass ejected from an exploding star or a destroyed planet will eventually reform into something new and continue the cycle.