Dyson is a 4X (explore, exploit, expand, exterminate) space game with unusual technology and a curiously serene feel. You play an alien lifeform that colonizes asteroids, but competitors are doing the same (RTS-like), and your ultimate goal is to exteriminate them.
Your mobile units are "seedlings," which both battle enemies and can be used to build "trees" on asteroids; it takes 16 seedlings to initiate a tree. Trees are of two types -- ones that create more seedlings, and ones that grow defensive pods that are launched at enemies attacking your asteroid. Asteroids range in size and energy, and can each support between one and five trees.
Trees grow fractally, with each leaf node capable of growing a seedling (or defensive pod), so that the rate of unit production expands with the age of the tree. Seedlings also grow in size and combat power over time. You do not control seedlings directly, but can direct those circling an asteroid to move to another one -- either all at once, or one at a time, or by selecting how many to move. Since an asteroid produces more seedlings only if there are fewer than 32 circling it, you want to do so, in fact.
When your seedlings reach an asteroid controlled by the enemy, they battle its seedlings there, then reduce its trees, then take over the asteroid.
The fractal nature of the trees and the procedurally generated arcs in which seedlings wander about their current asteroid, together with pleasant ambient music provided by Milieu create a curious sense of serenity, given that this is ultimately a game about conquest. It's also visually striking, perhaps even beautiful, when viewed at a close-in scale; much of the time, however, you're zooming out to get a better sense of the overall strategic situation, so some of that beauty is lost.
At the algorithmic level, Dyson is highly original, and it's no great surprise that it's an IGF nominee this year (and took second place in TIG's Procedurally Generated Content competition). At the strategic level, however, it plays very much like other simple 4X games like, say, Galcon. At present, there are five levels, each with slightly different problems for you to overcome; the developers promise more, but given the essential simplicity of the system, my guess is that at some point they'll have to add some additional aspects to the game to enable a sufficient variety in challenge.