Real-time strategy games have a fairly basic gameplay model: Acquire resources, build units, swarm the enemy. Dyson, a freeware game from Dyson Games, strips the model to the very basics. No cut scenes, no tech trees, no micromanaging miners or farmers. Dyson very deliberately steers away from much of the classic imagery to focus purely on gameplay.
The premise: You control semi-autonomous robots mining an asteroid belt. Beginning with a single world, you direct your swarms to either build "Dyson Trees" (which produce more units), "Defensive Trees", which can help blow up attackers, or explore other worlds. Each world is unexplored until your units get there, and this is where strategy comes in. Each world is rated for speed, power, and strength--and all units built on that world (there is only one basic unit) mimic those attributes. Want fast flyers? Build on a world with a high Speed value. Want tough tanks? Build on a world with a high Strength value. It takes 15 units to begin a tree, and each world can only have 5 trees, split over offense and defense, so build wisely. While there's only one "unit" in the game, the visual appearance is indicative of the overall strengths and weaknesses--fast units have bigger wings, for example.
Further, each world has a radius which limits how far units from it can be sent. Some worlds form, in effect, dead ends--no new worlds can be reached from them. This can force you to begin development in another direction. In Dyson, you tend to spread in a fractal fashion, with each world becoming productive and then sending probes to the worlds nearest to it, and so on.
Of course, there are enemies to fight. Some worlds are inhabited by your unnamed foe. In Dyson, there is no real management of units beyond "point them at the world." Once they're engaged, all units fight independently, destroying enemy units and taking down their trees (which keep them from spawning more units). Pretty much, whoever can arrive with overwhelming force, wins. There is no way I have found to intercept enemy units on the march.. er... fly... , so you need to watch the map for signs of conflict and hastily send in supporting troops. On large maps, you can find your attention diverted all over the place -- while you're marshalling forces for an assault on one world, you will find worlds on the other side of the map succumbing to the enemy.
Dyson is a much simpler game than Warcraft or Command and Conquer, but it does not lack for replayability, and it is being actively developed with new features. Gameplay is quick, making Dyson a perfect "lunch hour" game.