The quickness of a Flashgame but the strategy of a full-on wargame.
-small game >> quick to download and not much space used.
-simple to learn and gets you in the action fast.
-several different game types: Elimination, King-of-the-Hill, Gold-Mine, Target-Capture, Debt-Collector and a few others up to 4 players at a time.
-several skirmish maps, single player or multi-player (would be excellent on a game system).
-several Steam Achievements as well as in-game rewards that give you quick cash when you need it.
-general technology upgrade sysem
-Strategy is simple, yet deep.
-Difficulty setting matters; not only is the AI stronger but they're smarter. The higher the difficulty, the higher the rewards.
-If you're use to over-complex strategy games this will seem overly simple (possibly even boring).
-As far as I know you cannot play as the alien race, but maybe I haven't gotten that far yet.
-though planets do have a population, it is used only as a form of limiting currency in warfare. There is no real economic strategy except "make money >> spend it. Build population >> spend/send it."
All this said:
Nice, Quick, Simple yet Challenging.