In Darwinia you pitch up in a computer world under attack by a nasty red virus, and are tasked with helping its creator save the native Darwinians. It has strong RTS elements, but scales things down so you only control a few units, and increases your part in the action so that rather than just clicking your squad and clicking an enemy to get them to attack you directly control laser and grenade fire.
The prologue/tutorial is quite in-depth, introducing you to the various elements of the game, but I was somewhere towards the end of it when I had to shut down and couldn’t easily find a save option (might just be me, though). Next time I started it up the game crashed just after building a second unit (probably more to do with the crufty Windows install on the laptop than the game itself, it ran pretty smoothly with a couple of the options turned down), and with limited time I didn’t get back to it again. Still, from what I saw there’s plenty of game there for a most reasonable £5.99; it was released a couple of years back, and I remember PJ spoke most highly of it at the time. Another one I’m looking forward to returning to in a spare moment; an electronic thumb up, in between battling a virus.