Sin City is a nine-map episode for Doom II by Kurt Maples. From what I can gather, it existed in a variety of versions, each one adding more levels until this final, 9-map edition, released in '95. At the very least, levels 6-8 were produced after 1-5, and 9 was added to this set as a topper. The difference in mapping quality shows, too. The later offerings aren't knockouts, but they're better overall than the first segment, featuring better layouts, better action, and more cohesion. Overall, if there's one design element Maples falls back on, it's mazey corridors. He escapes this mapping trope in some of the later offerings, but if you should load up Sin City, put on your Theseus cap.
