In the field of computational complexity, most of the fundamental questions remain unanswered...so what have all those brilliant complexity theorists been doing for the past 50 years? In part, they have succeeded in painting a very intricate picture of the relationships amongst a wide variety of algorithmic problems. In Karp's foundational 1972 paper, he pulled the masks off of 21 familiar problems and revealed that, at their core, they are all just equivalent ways of encoding non-deterministic computation -- the adjective for such problems is "NP-complete." In particular, if you solve any one of them efficiently, you automatically prove P = NP. Since Karp's paper, thousands of household problems -- including almost all video games -- have been shown to share this underlying property. We'll discuss enough of these examples that, ideally, you'll be able to start noticing all sorts of secretly hard problems hiding in the most ordinary of places.