Looking for some confirmation (or telling me I'm dead wrong) on the specifics regarding the above-captioned-matter.
"Units that are on separate floors and directly above or below each other are not considered adjacent." ("Operation Cerberus" pg. 14, bold original)
Thus, one floor apart and not right above or below, but diagonally one away you are adjacent since "when two units are only one floor apart , floors and ceilings do not block line of sight". ("Operation Cerberus" page 17, bold original)
This makes sense to me, as I imagine the 3-D buildings to have a large central staircase connetcting the floors, which accounts for the "open middle" of the buildings, the ease of traversing floors from anywhere on the floor, and the fact ine can shoot diagonally down at an enemy, etc.
This would allow close attacks from one floor to another (throwing puches in the stairwell or whatnot, if not vertically collinear), but only if one initiating the attack is the one on the floor above because one must "remember that the unit on the lower level must add one to its range" ("Operation Cerberus" page 17, reiterating page 15 "How height Affects Range" rules letting us know that the rule applies inside as well as outside ) for not having the "high ground"
Therefore, with rules for this situation are maybe:
1.) The "height/range" modifier prevents close attacks initiating from any unit that is attacking from below.
2.) A unit may attack with a close-combat weapon line from one floor away as long as the units are "one away," but not directly above or below each other.
Once the unit with the "high ground" commences the close attack, the "lower-floor-unit" would still get a silmultaneous close attack since with C ranged attacks "the defending player can retaliate against your close-combat attack" and are resolved silmultaneously ("Core Set Revised: Rules of Play," pg 14), and therefore:
3.) Even if the "height/range" modifier prevents close attacks initiating from any unit that is attacking from below, if they are attacked from above by a close range attack, they may perform a silmultaneous close-combat attack of their own.
Seems a bit odd in practice, "you cannot reach up, but can reach down, unless they reach down in which case you can reach up."