Deadstone is a 2D shooter with RPG and tower defense elements that's now available for Windows. One-man developer Timeslip Softworks indicates an OS X edition is extremely likely to follow and there will also likely be a Linux edition. A playable demo is available, and they hope this will inspire support for their Steam Greenlight campaign. Here's word:

Mars is under siege, and the colonists are fighting a losing battle. Assume the role of Blake, a private security operative who crash lands near the colony of Deadstone after fleeing an outbreak on the Icarus space station.

Guess who just landed the job of sheriff?

To survive, you’ll need to use your combat expertise and lethal firepower, but to win, you’ll need a strategy. Manage Deadstone’s limited resources, investing in the right combination of defences, weapons, equipment, and upgrades. Develop the ultimate fighter to complement your strategy with the in-depth, but unfortunately named S.C.A.M. character development system. Every time an infected gets past you, a colonist dies. Can you stem the tide?