Why not rediscover a Real-Time Strategy Classic?
To get the free game: click me

The free version includes the classic StarCraft as well as its expansion, Brood War, which added a host of new content including three new single-player campaigns, new units for each race, and new multiplayer maps.
Play through a storyline that spans 58 missions spread across six campaigns, creating a true sci-fi epic. Follow Jim Raynor on his quest to save the Terran colonies from destruction; serve the cunning Zerg Overmind as it hatches a deadly plan; and lead the Protoss Prelates in the desperate defence of their home world.