This title can be played standalone [without purchasing Wings of Liberty], and it's good they did it this way. It's been called an "expansion", but it's really a game on it's own. Those who haven't followed the series can jump right in. It's smart to do that, because if they are going to wait 3 years for each release, almost everyone has a new or significantly upgraded computer at that point. As Blizzard has always done, SC2 runs equally well on WINDOWS or MAC. I was a late purchaser of this title, Heart of the Swarm, but am enjoying the reduced price as it was released March 12, 2013. Being a Starcraft fan since 1998, I have loved the game and all it's releases since it's early groundbreaking successes. When the new generation came out (Starcraft 2), it was a special time when the first in the Trilogy, Wings of Liberty (Terran campaign) came out July 27, 2010, then this title in March 12, 2013, then the long awaited Protoss campaign recently released November 10, 2015 - which I look forward to playing. As always, there are new units, new twists, new objectives/goals - not just in the campaigns, but on the Battle.net multiplayer modes. That said, the core of the game has remained solid since the beginning. What I was very impressed with in Heart of the Swarm, was the rich storyline, graphics/style overhaul, and the voice/acting talents are some of the best in the gaming industry. Blizzard has done well at weaving engaging storylines with strategic gameplay on the highest levels possible!