Take the all-time classic Asteroids, remove the ability to shoot things, and what do you get? A pretty boring game by the sound of it, but not so in the case of Variations on Rockdodger (VoR). This is a remix of the gameplay from the earlier -- you've guessed it -- Rockdodger, and although it doesn't have the most complicated gameplay dynamics in the world it's surprisingly entertaining. You'll need SDL to compile it: just run make and then ./vor in the game's directory after you've extracted it.

VoR places you in control of an anonymous metal sphere floating around in space. Well, we've all been there. From each side of the screen, rocks float into view and start to approach the path of your craft -- and then it's time for lightning-quick reflexes. Using the cursor keys, you can generate thrust from each side of your craft, moving it out of the way of approaching rocks to avoid any impact. If your ship touches a rock, a spectacular shower of pixels explodes across the screen as it buys the farm.

Nimble fingerwork with the keyboard will keep your craft free of rock impacts, but you can use the thrusters to push other rocks away, all the time making sure you're not heading straight into another asteroid blender. Describing the game here is like analysing a rush for a goal in soccer: you have a basic strategy, but in play you don't really think about it. You're running on pure adrenaline. It's superbly tough, yet when you fail you don't feel cheated, just outplayed.

There are a handful of cosmetic touches, such as the thousands of pixels that emerge on impact, but we'd like to see some beat-happy background music to really enhance the sense of urgency. VoR isn't the kind of game you'd spend £40 on, but it's fast-paced, difficult and addictive. Just beware of developing RSI!