The Eternity 2 (E2) puzzle has attracted the attention of puzzle fanatics, computer programmers, and mathematicians for many reasons, not the least of which is the $2 million prize for being the first to solve it. E2 is an edge-matching puzzle with 256 pieces. The general class of edge-matching puzzles is known to be NP-Complete, but it is unknown if there are aspects of E2 that can be exploited to make it tractable. In the spirit of cooperation, a few people have made their automated solvers available online, and I have provided an overview and back-of-the-napkin analysis of two of them. (more…)