"Fascinatingly charming" is how I'd describe this game. The retro graphics are vaguely evocative of Tron, and the enemies and characters are all subtle references/homages to video games and video game culture of the mid-to-late 80s and early 90s. There are Spiders and Centipedes reminiscent of Centipede, the Engineers which are evocative of Recognizers from Tron, even the Bombers that respond to Air Strike beacons look like they're right out of Space Invaders.
The Darwinians themselves are adorable. Though they have no animations and are simple 2D sprites in a 3D world, they manage to demonstrate a lot of personality. From the little mourning kites they release when souls ascend to the Central Repository, to the way Officer Darwinians chant out a marching cadence when issuing a "Follow Me" order, to the screams of horror and pain Darwinians have when terrorized with explosive weaponry and laser fire, you can't help but feel a little for the little guys.
As far as gameplay goes, it's very intuitive and usually pretty solid, some camera wonkiness aside. Managing a Squad is simple (Everything you can do aside from secondary-weapon switching is handled with two buttons) and intelligent use of Squads forms the cornerstone of gameplay. The game doesn't punish you for failure - replacing Squads is as easy as hitting F1, then clicking within a valid spawning area. You're encouraged to replace your Squaddies often and try out different tactics to accomplish your goals. All of the other units you can control are similarly uncomplicated, and the game gives you plenty of room to learn without holding your hand and beating you over the head with forced tutorials.
Darwinia encourages freedom of choice and lateral thinking in ways I haven't seen a lot of games do - stages are frequently nonlinear and the objectives can be accomplsihed in any order. Often times, you're simply thrown into a stage and challenged to figure out your own method for victory. Do you burmush your objectives or methodically wipe out the virus infestation between you and your target? Do you take your foes head-on, or can you sneak an Engineer around to a different comm port and use it as a second beachhead? Do you carefully avoid enemies in order to get a shot on a particularly annoying foe unopposed, or do you just carve your way in?
All in all, Darwinia's one of the most refreshing tactical games I've had the pleasure of playing, and I heartily recommend it for anyone who enjoys a little old school nostalgia, adorable faux-retro graphical charm, and solid gameplay.