I've implemented a more complicated game model, with hyperspace, truespace, and planet-view, like sc2. All is seen in top-view mode.
I use the timewarp algorithm, so ships are rotated 64 frames when loaded, or they can be pre-rendered, in 64 frames; and then it's only a matter of scaling. On top, each frame is cached, so that scaling doesn't have to repeated again and again if it's not necessary, you just draw the cached bitmap.
Planets are calculated real-time, and rotate. Their image consists of a 2:1 ratio rectangular bitmap, which is projected onto the screen in a circle, as if it's 3d.
These are my gameplay ideas, I keep them simple, at least for version 1.0 of the game:
I'm not planning to include research.
Building can only be ordered from homeworlds, and take time to build (time is the only resource).
Colonies can speed up building on homeworld (how much faster depends on the race).
Each race has 1 fighter ship type, 1 colony ship type, and 1 construction ship type (for constructing 1 type of defence struct).
You can diversify your fleet by allying or conquering other races.
I gather that one race has a certain liking or disliking of allying with another race. I'm not sure how to do this, yet. Perhaps it just influences how many ships you must destroy before they join your alliance, or how much you've to pay (e.g. a number of colonies).
I'm planning to force some strategy in the game, by disallowing ships to fly far from homeworlds or colonies. When they travel, they've to make stops at colonies to refuel. In that way, you can create strategic crossway points which one can defend.
Life: I let life depend on the type of planet surface, temperature on the planet, and/or presence of an atmosphere. These lifeforms are viewed top-down, and consist of about 4 bitmaps which form an animation.
In principle I can make a game with a very large starmap and many ships ; I've not reached this stage yet and don't know how many ships there can be, realistically, as all has to be calculated in real-time.
For AI, I'm using a hierarchical model (kinda like squad-ai):
weapon - ship - fleet - commander - race,
so you've race AI which determines very general strategy, some kinda commander AI which orders fleets, fleets which order ships if they enter battle, and ships use their weapons. In each layer, a decision is made about the behaviour of a "lower" entity. This is in very early early stages.