No loading screens, No waiting betweens levels... No breaks in the action. That is the aim of DOOM:ONE. I am working on a beta release version of the complete episode now. The 4 level demo is available,which explains what I am trying to achieve here better than I ever could! I have found its best to play this with the Brutal Doom mod installed, however it is not required. This will be released as a PWAD that will work with ZDooM and Zandronum, due to the scripting involved in tying everything together.
Software that can be used as an alternative to Doom One: