Hi! I've been wanting to create a similar mod since the release of Space Age, but it's great to see someone else do it! I noticed (while casually downloading the mod and viewing the code) that the mod references Space Age prototype definitions (like asteroids) in plant.lua (likely a misspelling of planet.lua, you should fix that too) and even the core mod, without depending on them in info.json.
Instead, replace the dependencies line with this:
"dependencies": ["base >= 2.0", "space-age"],
It's always good practice to depend on the base mod, even if you aren't directly referencing or modifying it's prototypes.
