The Real Texas is an upcoming adventure game which will be available for Linux, Mac and Windows. The game looks quite interesting with some features that makes it different though it is an old school top down adventure at heart. (videos below)
Sam, and ordinary Texas rancher, is on holiday in England when he falls into a blue portal and lands in The Strange Texas which is really just a sort-of satire of his own real world.
The gameplay is similar on the lines of The Legend of Zelda: A Link to the Past and Ultima VI with some interesting twists. There are no swords in the games. The hero uses a gun and the controls are similar to FPS games where you move the hero with keyboard and shoot/aim through mouse.
There is no health bar and the combat is intuitive depends on right strategy, reflexes and luck. So the right way is to get into combat rhythm and not to slog it out.
The game involves usual adventure game stuff like rooting through people's houses, collecting items, and getting clues from NPCs. There are also lots of side quests, secret hunting and easter eggs.
Though there is no demo available as of now, you can have a look at official gameplay videos.