Invisible, Inc. [official site] is a turn-based stealth game about guiding variously equipped corporate agents through procedurally generated office buildings to hack computers, steal information, and get out again alive. It was our Game of the Month for June and is one of the best games of the year. And it has an expansion out tomorrow.
Contingency Plan adds four new agents to control, new weapons, items and augments, and more levels for the existing campaign and endless mode.
There's a full list of the new features on the game's site. It's not world-shattering stuff, but it's adding more diversity to a game whose underlying systems were already sound. I like the idea of lengthening the existing campaign with new mid-way missions, rather than continuing the story at the end, because of the way the game encourages re-plays to try different characters and is already kept fresh by the level generation. I'm also sure that players better than me will like that the endless mode will carry on to greater difficulty levels.
Invisible, Inc. has a smart, tightly-wound design that presents you with every piece of information you need to succeed, but it still produces moments of high-wire tension as you try to think your way past security forces, and cascading slapstick failure scenarios when you get caught. That makes the agents the most exciting addition. The existing roster of characters are great, but it's their different abilities that often defines your approach to the stealth challenges you encounter. New characters means new approaches.
You can watch old man Quinns talk more about what makes Invisible, Inc. great in episode 3 of Cogwatch, our series examining individual mechanics in individual games: