I'm thrilled to see a board game pop up on Ludum Dare! Good for you, and makes me wonder if BGG should organize something similar for board games.
Have some specific feedback on the game after playing a test round against myself. Overall I think this is a good start but I'd like to see the idea fleshed out further:
* Victory conditions aren't clear. I'm assuming "When last of your planets is gone" but then you don't start with any, so that's a bit odd.
* Are the rules for the "Create a Planet" card the same as for regular planet placement? If so, there's not much point in playing that if could very well help your opponent.
* I find roll-based movement to be really annoying. Coordinating a planetary invasion is VERY challenging as a result.
* I'm assuming units are stackable everywhere and not just on planets?
* Overall, the game is very much a game of chance driven by the die (especially in planet placement). I'd like to see more determinism and less randomization.
Good stuff so far! Keep working on this idea.