Thanks! Yeah, limiting scope is something I still have to work hard at; I think the weekly 3 hour jam can be a good way to practice planning and executing really tight games.
You're right, the spawn is time based - planets are spawned at random intervals and given a random y position, but the x position is always a fixed distance in front of the player. So if you stayed perfectly still for a while, you might end up with a wall of planets when you start moving again.
I think if I'd had more time, I'd have liked to instead use random "chunks" of preauthored stuff to guarantee more fun bits.