okay, some ideas about levels...
ultimately every level should be interesting and different in many ways. in fact this will mostly obsolete current specil_levels system... i think it would be cool to firstly decide on the type of a level, that shoul be generated (it's already implemented: complex, maze of rooms / etc). then accordingly to a level type optionally divide it into number of zones (not many - 2,3,4) and then decide what each zone will be... also each zone could contain some small stuff, like 'rooms' mentioned above. rooms of course are not a prerendered patterns, but a general idea.
example based on what is currently implemented:
level type - former human base
three zones divide it vertically, one of them iz maze of rooms, the other two are complex. each zone could have its own flags like lotsa_barrels.
in each could be rooms like vaults etc...
some other example which in fact forgets about special levels to use them as parts: =)
level type - HellBridge (has a river of lava going through center of level vertically or horizontally, or even maybe at angles if the developer is workaholic =). also has a bridge or a couple). the two parts that are separated by river could be chosen from standart zones for HellType levels... this could be hellish caves, hell city, hell hall (some big building which may have some small rooms and a big one in the center), hell armoury, mortuary (little one), pillars (kinda like in hell's arena, but more interesting), etc...
okay... RNG chooses... ummm... okay - pillars and HellHall (to make things really new =) )
of course the zones could be of the same type, like two caves... (oh, the caves are not so good idea in their current implementation - they are not open).
so... pillars and HellHall.
pillars: some masses of walls in blocks like you've seen in Hell's Arena, some a bit bigger, some very small. some pillars could be connected using a standart wall. some pillars rarely could contain 'secret' stashes in them (so thay are either destructable, or have destructable parts). splashes of lava may apply like in current Hell levels. maybe a lonely small building packed with monsters could be found (The Keepers Of The Pillars) =)
HellHall: 1) generate some huge rectangle building with some doors, but leave some place outside (will be needed later). 2) make the roads of blood (maybe mixed with lava) go from doors to the central area of the building. 3) make some side rooms adjacent to walls, using the space not used for 'bloodroads', some of these rooms could contain some specialities (could use standart room routine for them, or a bit tuned one, like no_circle_rooms, no_vile_lairs, etc =) ). 4) make some rooms outside of main building, these rooms are smaller, could have doors outside, inside or both. so the Hall will not be a plain rectinagle if seen from outside =) 5) the center area - some variants... in fact if some monsters tend to keep in the center of a map (i dunno if its optional in current AI system) - then if this HellHall zone is only one on entire map (then the level type would be like PlainSingleZone) - the center area could be a lake of lava and blood with lots of lost souls. otherwise it could be just some stash and monsters. or have an always_special_room in the center (choosen from standart special rooms). or have some single char walls with monsters behind, like this:
# # #
# m# m #
# #^ # #
m #m
# # #m#
# # #
damn, i must haven't slept for too long =) hope my english is not so bad... =)
of course all of it are just general thoughts and it would be really hard to implement an ultimate level system, but i think that some step to it are not so brain*arch-vile*ing. =) the current level generation system is too simple. replayability is one of the coolest parts of roguelikes and different levels make it way much better.
P.S.: hell, why didn't i browsed forum in case a thread disscussing that issue already exists?.. hope not =)