Portal has become something of a sacred cow in the video game industry. Nobody wants to compete with it, and for good reason. Valve's critically-acclaimed first-person physics puzzler is a class act. So who better to further populate this niche subgenre than a team headed by Portal veteran Kim Swift? While Quantum Conundrum isn't on the same level as its cousin, it's still a charming and inventive adventure that everyone should at least try.