I love Steam for their occasional deals, such as the recent Indie Game Pack they had on sale for $7.99. The pack came with a number of independent games, including Galcon Fusion. If not for that deal I would have never known what a great game I was missing.
The game play is fairly simple, in theory. Galcon Fusion is a RTS game set in space. Games start with each player controlling a planet (or multiple planets, depending on the settings). The number shown on controlled planets represents how many ships you have on that planet. Controlled planets also generate new ships, the larger the planet, the faster it generates ships. Neutral planets that are not owned by any player show a number on them, representing the number of ships you need to take over the planet. Clicking on one of your controlled planets and then right clicking a neutral or enemy planets sends a percentage (which can be changed from %5 to 100%) of ships, represented as triangles, from your planet to the neutral/enemy planet. If you send more ships then the neutral/enemy planet has, you take it over. The goal being to take over all the planets on the map.