Favorite PC game of the moment!

As the tittle says...

What is you absolute favorite game on this moment.

If different kind of games, you can divide it up into the genres of games.
for example i like sandbox games and strategy games, but also puzzles.
Therefore my favorite would be:
* Cubic Castles - Sandbox
* Age of Empires - Strategy
* Maxi jigsaw puzzles - Puzzles

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What is your Favorite?