One map, fully compatible with DooM2.exe, while including as much detail as possible. This map is different from most other maps in that the player progresses differently through the map depending on the skill level. Each skill level "starts" the map at a different location, and some of the traps are skill-level specific. Additionally, the keys and weapons are at different locations for the different skill levels, and there are some areas that are only accessible to specific skill levels. I encourage you to play the map at each of the 3 skill level groups -- 1/2, 3, and 4/5. Note, that while skill levels are incorporated, Skills 1/2 are definitely not for the faint of heart -- in most other maps they would probably play out at Skill 3. Skill 3 is slightly more difficult than Skills 1/2, and Skills 4/5 is slightly more difficult than Skill 3, but none of the skill levels is terribly difficult.
