Technically, we played what these days might be called OD&D1974, but what the players wrote on their notebooks, along with name, as in school, was in fact Ur-D&D, so I went with that. As I have mentioned elsewhere, this small mini-campaign has some specific pragmatic constraints that it must fulfill. As such, I use the Ur-D&D rules as I have been using different D&D rulessets since I started DMing: to represent different eras in my ongoing campaign.
This approach makes using anything apart from Chainmail and the basic set anathema, as this preassumes too much: If there are demons the timeline has already advanced too far beyond the Age before Ages etc.
As I also mentioned elsewhere, I had some troubles in designing the first Dungeon, so I reversed the process and came up with a nice „new“ way of doing it, conceptually and manually. I rolled up the room contents and matched the results one around my central concept and the most important rooms, and so on. That worked better for my way of thinking. Manually, I put the dungeon map into a sheet protector and wrote with erasable markers on the protector to move around treasure, traps, monsters and try out some more configurations and to add notes for room contents, patrol schemes, mechanisms etc. That felt very natural and the creatice juices flowed more freely than with any other method of dungeon creation I tried so far.
My real point, though, is the fact that Ur-D&D is for girls. Quite literally, the reason I chose a different era and rules set was that we would have some more non-adventure gamers joining for the mini-campaign and they happen to be girls. Turns out, my decision was right: The new players could interact with the dungeon environment immideately, without first learning a layer of rules or being patronised by the older hands. Also, the older hands got more creative too, as the shackles of 3.5 went off: the combat order was overturned and turned into a more freestyle affair, ideas were tried that in 3.5 would be usually shot down by: you’d need a feat or suffer -4 etc.
Apart from that, it pretty much played like the D&D we knew, because I already DM as D&D should be DMed. The combats were a little bit more intense, and as I described the dungeon and only put out the map tiles if there was a combat, the dungeon was really explored. The interaction with the environment was highlighted a little more than usaul in our games, but I fear this will wear out fast. As someone elsewhere said: there are only so many pit traps and so mayn creative ways of searching for secret doors before you go back to a simple roll. Apart from that, the most enjoyable part was to DM the combats, as they were about weapon and formation interaction instead of Feat & Spell interaction as it is with our high level games. Ur-D&D will not be much different at 17th level in that regard, but the Chainmail based combat and the high stakes enabled different tactics. In hindisght, this is how our combat was handled, it evolved into that pretty quickly, informally:
a) check for surprise
b) both sides roll 2d6 for initiative
c) he who has initiative has nothing else, i.e. he has the first chance to dictacte the course of the combat round, a true first strike it is not (1min combat etc.)
d) first side acts, declares what they want to accomplish
e) second side frantically describes reactions, if any. A reaction at this time means forfeiting your own action. If weapons are involved the chainmail range classes are used to determine speed of the weapon. For example, Orcs with spears could not be hit as a reaction, but their spears could be targeted. OTOH, if the weapon classes had too high a difference you might get a free strike. Example: spear against Giant Rats.
f) remaining figures act
g) morale checks are made
h) goto b)or end fight
Other rulings that had to be made:
– decision on the exact working of turn undead (undead will cower, but will strike back at anyone except the cleric)
– decision regarding what happens if a healing potion is split among two people (1d3 for each)
– decision what happens on 0 hitpoints (as Chainmail is supposedly realistic, and most casualities in medieval times were from after the battle, you fall down, only a coup de grace will kill you, instantdeath only at -HPmax)
– decision on bandaging (regain 1 HP but only from cuts and only once)
– decisions on grappling, rear attacks and subdual of enemies (half damage and saving throw agains para to remain conscious)
While this is nice and fun, I definitely see why there was an AD&D and a 3.x. Some questions arise so quickly, answers are needed that DO NOT take away the freefrom part. Turning undead would be the most important example, I would say. Handling this ad-hoc and differently each time would be rather strange. And from there it is a slippery slope…I’ll let you know how our house rules evolve.