Evoking memories of games like Geometry Wars and Tilt To Live, Radia [Free / Free] takes the tilt-based "survive as long as you can" mechanic out for another drive, and the results are comfortably non-threatening.
In Radia, the primary objective is to tilt the device to guide a small circle through a level, collecting the luminescent "radia" that spawn around the playing field. Each level introduces a different layout of walls that offer up a very Pac-Man-esque design aesthetic, while haranguing the player at every turn with ghostly sawblades sent adrift across the landscape. The main catch of the game: the player must navigate through the confines of the maze-like level, while the blades can pass through walls.
Visually, the game is simple and pretty, with the usual assortment of neon-retro design, like the sort used in the aforementioned Geometry Wars, or Pac-Man CE. Animation is crisp and smooth, nothing particularly stands out - either positive or negative.
The gameplay is very easy to pick up right away, and the higher levels introduce various tricks and powerups that keep things feeling lively enough. In one level, you may be confined to tight corridors with radia that rapidly appear and diminish - in another, the radia are encased in walled off boxes, which slowly disappear, allowing you to collect the treasures within. There's always a sense of impending doom - move too slowly, and the radia will deteriorate, keeping you from your three star score. Move too quickly, and the ever-faster sawblades will carve you to pieces, ruining your run.
The controls are excellent, provided you understand one point - the tilt mechanic appears to be reset at the start of every level, using whatever the current angle of your phone is as its neutral point when the level begins. This is never explained, and can lead to some unbelievably frustrating situations. On more than one occasion, I managed to instantly screw myself over by holding the phone level with the ground at the exact moment the level started, completely throwing off the controls, and managing to launch myself with reckless glee into the waiting teeth of a saw blade.
More options for the controls would take away some of the offputting issues with handling, and this is exactly the kind of game that would be a shoe-in for user-created levels. There are a lot of good ideas here, they just need to be fleshed out a little more.
Those minor suggestions aside, while Radia isn't setting any new trends it's certainly not a bad title. In addition to the standard level mode, there are Timed and Endless survival modes, which give you a good opportunity to brag to your friends. The standard level mode promises more levels coming soon, so there's plenty of reason to feel justified for your buck.