First is Grid Wars 2, a game by Mark Incitti, which he was forced to remove from his site because of its resemblance to a game called Geometry Wars, which is a bonus game hidden inside an X-box title. How this competes with that, I'm not really sure, as it's distributed for free and incorporates many improvements, but we can at least be grateful that it's still available from World of Stuart, which has an excellent article on this amazing game. The gameplay is pretty simple -- shoot everything that moves and don't let it touch you -- but the stunning visuals and lightning-fast pace make this game incredibly satisfying and very addictive. I also like the many custom options, like the size of the field, maneuverability of the craft, various scoring and difficulty options, the style of the grid, even the type of light sparkles. Go get this game while you still can.
If you find you need a break after all that stress, try Tranquility. Gentle, soothing music plays while you navigate your way through space and towers of floating platforms in search of the spinning star that is your goal. Movement through this low-gravity environment is a combination of drifting, floating, falling, and flying, as you bounce off the floor or the colored platforms to gain altitude and slowly glide downward in a controlled fall. It's quite tricky at first, but wonderfully liberating once you get the hang of it. One of the first lessons of Tranquility is simply: slow down. The faster you move, the faster you fall, and hasty maneuvers can send you quickly spiralling out of control.
While you must download the application to play, the actual levels are accessed online, through a subscription service ($6 for a lifetime membership) -- but for the occasional player, there is a new series of free demo levels to play daily, which has usually proved adequate to satisfy my needs. Especially when you're first starting, a day's worth of levels is more than enough of a challenge to master. As a bonus feature, the application has a "TQRadio" feature you can use to listen to the game's new-agey music in the background whenever you like. The game also features a nice wide range of options so that you can play around with the music and visuals.