If you don't have these game get them now. They are all premium Indie arcade games. My favorites are World of Goo and Anomaly: Warzone Earth. The latter is a Tower Defence game.
Anomaly: Warzone Earth:
Anomaly: Warzone Earth is an extraordinary mixture of action and strategy in a reversed tower defense formula. The game tasks you with saving a near-future Earth from an alien onslaught. The invaders have captured world’s major cities, building huge turrets that destroy everything in their path. It’s up to you to lead an armor squad through the streets of cities like Baghdad and Tokyo, planning the route and strategically choosing which units to deploy in order to crush the opposition. Take control of the Commander, whose special abilities and quick thinking will be vital in supporting the squad in its mission, as you engage in fast-paced, tactical battle across story campaign and two heart-pounding Squad Assault Modes.
Key features:
Enjoy innovative game play – mixing action and strategy in a reversed tower defense formula – you’re the attacking side!
Play the commander whose special abilities and quick thinking are crucial to support the squad in its quest for victory.
Think tactically and strategically, choosing the right squad and the best route for the mission.
Extend tactical possibilities by gathering resources to buy new units and upgrade your squad during a battle.
Play for hours on end in the engaging story campaign, as well as the two exciting Squad Assault Modes.
Immerse yourself in the game with great visuals and atmospheric audio.
Supports PC touch screens compatible with Windows 7! Tap the screen and enjoy full tactical experience.
Edge:
EDGE, the award winning retro-styled platform game has been extended!
Download the free EDGE Extended DLC containing over 40 brand new levels, additional music and all-new races against the notorious Dark Cube!
In EDGE players take direct control of the cube and roll their way around the game's dozens of levels. Search for all the prisms, find the shortcuts to improve your times and compete through the Steam leaderboards!
World of Goo:
World of Goo is a multiple award winning physics based puzzle / construction game made entirely by two guys. Drag and drop living, squirming, talking, globs of goo to build structures, bridges, cannonballs, zeppelins, and giant tongues. The millions of Goo Balls that live in the beautiful World of Goo are curious to explore - but they don't know that they are in a game, or that they are extremely delicious.
Mysterious Levels - Each level is strange and dangerously beautiful, introducing new puzzles, areas, and the creatures that live in them.
World of Goo Balls - Along the way, undiscovered new species of Goo Ball, each with unique abilities, come together to ooze through reluctant tales of discovery, love, conspiracy, beauty, electric power, and the third dimension.
The Sign Painter - Someone is watching you.
World of Goo Corporation - Congratulations! World of Goo Corporation is the Global Leader in Goo and Goo Related Product, including World of Goo Corporation Trademark Brand Soft Drink Beverage and World of Goo Corporation Trademark Brand Facial Exfoliating Lotion. Succulent!
Massive Online Competition - Human players around the world compete in a living leaderboard to build the tallest towers of goo in World of Goo Corporation's mysterious sandbox. World of Goo Corporation is contractually obligated to state that everyone is a winner and is enthusiastic to celebrate everyone's tower building opportunities equally.
Osmos:
Enter the ambient world of Osmos: elegant, physics-based gameplay, dreamlike visuals, and a minimalist, electronic soundtrack.
Your objective is to grow by absorbing other motes. Propel yourself by ejecting matter behind you. But be wise: ejecting matter also shrinks you. Relax - good things come to those who wait.
Key features:
Independent Games Festival finalist in three categories: Seumas McNally Grand Prize, Excellence in Design and Technical Excellence
Progress from serenely ambient levels into varied and more challenging worlds. (47 levels, plus bonus content)
Confront attractors, repulsors and intelligent motes with similar abilities and goals as you
Selected as one of the 2009 PAX 10
Procedural content: play random versions of any level
Sublime electronic soundtrack by Loscil, Gas/High Skies, Julien Neto, Biosphere, and more
Dynamic time-warping: slow down the flow of time to outmaneuver agile opponents; speed it up to raise the challenge