Crapi

Crapi is an experimental multi-level PWAD developed for ZDoom from 2003 to 2006. It is split into two episodes and features 29 levels, including several secret and deathmatch-only levels. It is notable in that the focus is on exploring a vast and extremely non-linear world (most levels have at least 3 exits). Crapi features an unusual progression system in that most maps can be re-entered but with the caveat that this will restart them, resetting all monsters and geometry changes, with the exception of marked Z-Doors and doors and switches requiring the yellow skull key. While some new graphics were added, level designs are mainly techbase-themed, but greatly expanded and mixed with elements of natural caves and canyons. It also contains many new monsters, both brand new and from the Monster Resource WAD, though many from the latter end up being unused. The project saw several patches, as the initial release had an error involving two copies of MAP01, one of them being a blank map which thus overwrote the first level.