In the meantime here are a couple of color studies for 2D planets:
Which of the following two options would be better?
- Always show planet in cross-section
- Have a foreground layer that fades away when the player is underground
A foreground cap could add to the exploration aspect of the game by hiding underground tunnels. On the other hand I'd have to draw a spherical planet on it or something, which would be tricky to do well.