I've built the core engine of a real time strategy game. What's next?
I think the main player interaction is going to be be writing instructions for ship autopilots. Things like "go to planet x, pick up 10k units of gold, fly to planet y and unload, repeat", although I want the ships to be able to make choices based on market conditions.
That last point implies the existence of a market. Eve does it well, with a big range of player made goods, which implies:
* Manufacturing/Tech tree
Not sure if the player will need to get recipies, but I'd like a big tree (graph, ideally) of make a to make b to make c.
Need to stop the player from just building huge stockpiles of stuff. Tax is always fun ("The Empress demands you pay x credits per citizen" where x is just a little to high. Let one planet get rowdy enough that a black market develops...)
* External threat
Need to balance growth with security. Pirates are fun, but they're more of an internal problem. Neighboring regions getting pushy is potentially good ("Your military buildup is concerning the Empress and she demands an explanation."). Other ideas: aliens (obviously), grey goo, plague, religion (those three are mechanically similar)
* Next steps
Build a small universe. Three or four systems, fairly balanced. Get basic ships working, and get some UI ideas roughed out.
Think about resources, industries, and recipies. Systems should either be self-sufficient with a small surplus, or able to generate a useful surplus with a chunk of investment.
Think about the theme/background. Get more of it written down.