Savage Moon
One small step for tower defence.
You all know the drill by now. Whenever you go to space, especially if you live in a resource-starved future universe, and find an almost limitless supply of metal/gems/food/adorable fluffies, you're probably about 24 hours away from having a vicious, multi-limbed alien monstrosity clawing your face off.
It should be no surprise then that the titular moons of this PSN effort are very, very savage indeed. The thin smear of narrative horseradish on the gaming beef is that you're out in the cold reaches of space, mining precious resources from rocky, inhospitable moons. Said moons are also home to hordes of furious, suspiciously well-organised alien bastards who want nothing more than for humans to pack up and bugger off. However, in true colonialist style, it's your job to subjugate these uppity natives in order to ease the progress of resource-stripping. This is done via the medium of tower placement, defending your precious mineshafts from the advances of the hungry Insectivores.
Much like PSN compatriot PixelJunk Monsters (which will crop up rather a lot, I'm afraid), Savage Moon is based on the venerable tower defence genre, which consist of a maze-like environment, with multiple paths towards whichever goal you're defending and a source of enemies at the other end. Limited resources are granted to the player in order to construct a network of towers along the path, shooting stuff at the bad things to stop them getting to your base.
It might not sound particularly appealing on paper, but as a genre, tower defence has been responsible for more lost man-hours than the brown acid at Woodstock. It's a popular business, and PixelJunk Monsters is widely regarded as one of the PSN store's better offerings.
Savage Moon's take has a surprising level of depth. More RTS-lite than tower defence-extreme, players control a very functional cursor - navigating around rocky moon maps with a flexible camera, zooming in and out and placing towers in strategically advantageous positions. This can be on top of rocks, where ground-based enemies will be unable to attack them, or right on the ground where they can. Safe space is limited, and often towers have to be unceremoniously dumped directly in the path of the alien advance.
Initially there's only one tower available, the slightly wimpish machinegun turret, and two additional upgrade levels with which to beef it up. Earn a bit of cash by exterminating a few of the very Starship Troopersy bugs and you'll be ready for the research screen. Research allows you to develop new weapon types or increase the upgrade cap. Eventually you'll have a wide range of armaments to choose from, as well as blocking towers and repair units. Slap down increasingly powerful turrets to swat the increasingly tough Insectivores until the 13 waves of beasties which infect each level have exhausted themselves, then move on to a new moon.
And that's it. Rinse and repeat.
But it's the thoughtful little extras that make Savage Moon a potential long-term partner. First and foremost is the command priorities system, in which one of three aspects - cash, defence and attack - can be boosted at the cost of the others. More flexible than it sounds, the command priorities are usually an early grab for cash followed by a push for damage late on as you desperately fight off the tough and numerous end-waves. Once enemies start shooting back later in the game, like the cowardly scumbags they are, defence becomes a priority. It all helps to fine-tune strategy no end, without the hassle of selling and repositioning turrets placed without due care and attention.