Quote from: 1stLevelWizard on December 10, 2023, 07:39:36 PM
In my estimation, I think what makes a game OSR compatible is whether or not it's trying to corral the players into the OSR playstyle. I'm sure my definition of that playstyle won't be agreed upon by everyone, and I'm not trying to start any flame wars here, but I'll take a crack. The OSR playstyle is that of dungeon-crawling and exploration, with the eventual aim of creating a player domain. This is all held together by a rules set that isn't rules light, but isn't so airtight that you can't change them without derailing the rules set. This isn't a perfect definition, but it's what I'm gonna work off for now.

So for an example: I'd say B2: Keep on the Borderlands and OSRIC are compatible with the OSR, but Red Hand of Doom and 4th Edition D&D are not. But if a game swapped Strength for Power, or used ascending AC over Thac0, that doesn't really make a game non-OSR.

I largely agree.  If we were to create character sheets for game styles, I don't think AC vs Thac0 would make the cut.  My list would be something more like:

1) Progression.  What is the nature of the path to PC godhood?  Do they start there or do they work at it?  Do they move at the same rate out of a sense of fairness, or progress asymmetrically because that makes sense for the setting?  Is it entirely their own doing or a combination of environmental factors (equipment, gods, etc)?

2) Purpose.  Why do these characters do what they are doing?  Are these simulations of what being in that world might be like, or are these representations of what our current world looks like?

3) Mechanical tightness.  Rulings vs rules.

4) Balance.  To what degree does fairness to the people playing the game change what makes sense in the world?

That sort of thing.

Quote from: Socratic-DM on December 10, 2023, 04:11:27 PM
I'm also taking into account RPGpundit's adviice, everything really should consider early D&D in it's design phase, and I'd like to make something that has very different mechanical expressions, but which can really easily or on the fly use OSR D&D content.

I ran GURPS for 20 years and before that Fantasy Hero used the same setting I used for my AD&D 1e campaigns (The Majestic Wilderlands). Then around 2009, I returned to D&D using OD&D/Swords & Wizardry to create my Majestic Fantasy RPG.

Along with that I created some adventures like Scourge of the Demon Wolf that I ran under multiple systems.

The first thing is to ditch any idea of mechanical equivalence. Instead what you want to do is look at what an adventure or setting means as if you were there looking things over.

First the characters, are they novices? Perhaps journeyman level of skill? Masters at their profession? Finally, maybe they have skills that are considered at the level of the Nobel Prize or the Olympics?  Next are the creatures. Are they creatures that a novice can take on, a journeyman, and so on? The environmental challenges can be considered in the same light.

When I leap to a new system, I first identify who are the novices, journeymen, masters, and elites. Then I look at the creatures and environmental challenges. I see how that lines up with what I did in the past with the Majestic Wilderlands. It doesn't have to be exact but there is a point where I will jettison that element of the new rules and make something that fits what I did in the past.

But you are making a new system so while it is a lot of work you have the advantage of tweaking things without having to uphold other folks expectations of the system.

Some things specific to classic D&D.

For characters I consider the experience range to be as follows
1st to 3rd Novices
4th to 6th Journeymen
7th to 9th Masters
10th to 12th Elite (Nobel/Olympic)
13th to 16th The Best of Best only a handful appear each century.

First from OD&D to AD&D 1e (original 3 books), characters are heroes, not superheroes. A mob of Novices and Journeymen can take down a party at pretty much any level. However, keep in mind this will rarely happen to a smart group

Generally using OD&D 3 LBBs as a foundation comes the closest to how more gritty RPGs like GURPS, Runequest, and Harnmaster play out. OD&D + Supplement and B/X are OK, AD&D 1e if you don't use Unearthed Arcana and the later Monster Manual works as well. This is mostly because the AD&D Monster Manual was written first, it retained a lot of its OD&D roots.

For your 3D6 game you will want to consider the following categories of elements.

Characters
Monsters
The Environment (Traps, and other challenges)
Magic
Treasure.

One factor to consider is that classic D&D has magic that works well for mass combat. Fireball, Cloudkill, etc. Most other fantasy RPGs tend to tone down their magic in that regard. Mages are still formidable but more as individual combatants.

Pay attention to what works in classic D&D as far as creatures (and characters) operating solo versus in groups.

Pay attention to the fact that in classic D&D the preferred method of power gaming is the acquisition of the "right" set of magic items. For your 3D6 system, you want to make sure you have a similar range of magic items.

A lot of folks will tell you that the solution to powergaming is to make magic items special and rare. But that is a bit of a bullshit argument as there is no size fit all campaign solution. Set up your recommended treasure distribution but account for when campaigns are more generous with the magic items by tweaking the actual list itself.

For example for my Majestic Fantasy RPG, I started with a range of +1 to +5 magic items. But after the 2nd playtest axed the +4, and +5 bonus (and their miscellaneous MI equivalents).

I found that if you play long enough, eventually the players will acquire some type of ideal assortment of magic items.  Whether it is GURPS or OD&D.

Last and most important, is playtest, playtest, playtest. Both with your new system and an edition of classic D&D. Run the same adventures, and setting for both. The reality is that design prowess is only going to get you so far. There is no substitute for experience through actual play.

While I have 40 years' worth of experience in this, I was able to get up to speed with developing my Majestic Fantasy OD&D in a far shorter time by paying attention to the details and running multiple campaigns and sessions at conventions.

The Majestic Fantasy RPG, that I wrote is a reflection of how stuff worked in my GURPS campaign. The classes are translations of templates I used. The brand new stuff I added were things that OD&D didn't handle like skills for stuff outside of combat and spellcasting. 

I was lucky that through my own work or finding stuff on the GURPS forums I continued to adapt D&D adventures when I didn't have time to fully prep my stuff.  So it was easier to backport to OD&D when I started that project.

I also helped Douglas Cole of Gaming Ballistic with advice and tips for converting his Fantasy Trip Solo adventures over to Old School Essentials (B/X). One tool I showed him was this
http://www.batintheattic.com/dnd_combat

This allowed to play with some number to get a baseline on different power level in classic D&D.

Hope this helps.

If Runequest is included (and it should be, having its origins in the 70s) then the amount of compatible material is pretty massive from that angle as well.

Quote3) Mechanical tightness.  Rulings vs rules

This is a good point too. It's not necessarily rules light, but the rules are much more open ended. As a player of 3rd and 2nd edition, I can say that while 2nd can be meaty, it's more often than not a concise set of rules. There's room for DM fiat without missing out on important rules.

It's like how someone mentioned that a 5e/3e statline is much meatier than a BECMI statline.

Compatible?

Most games that are compatible to TSR D&D say so (albeit indirectly) on the cover, blurb or DTRPG label.

Runequest is old school but not "compatible" with B/X, and 3e is not exactly compatible with TSR either - 4e is not even close.

TFT is closer to GURPS than to D&D IIRC.

I think for a game to be compatible it needs easy, on the fly, conversion.

Of course an experience GM (such as estar and douglas) can do this with any two systems, but compatibility means "easy to convert" IMO, and Runequest/GURPS are not that easy to covert to D&D.

"Fighter 3" means nothing in both those systems, but it is a thing you can find in a TSR module.

Otherwise, you can convert anything by simply swapping a TSR goblin for a GURPS or Dungeon World goblin. You can convert anything to RISUS because it is a very easy system. Doesn't mean the systems are compatible.

Quote from: Eric Diaz on December 11, 2023, 04:33:03 PM
Otherwise, you can convert anything by simply swapping a TSR goblin for a GURPS or Dungeon World goblin.

Your mileage will definitely vary once you go further than a goblin.

I'll soon be wrapping up a PF(1e) to D&D 5e converted game that's had quite a few warts due to the conversion.

One big difference is how Pathfinder provided you with many, many rooms of monsters to wait patiently to be killed by the PCs.  There wasn't any other way to level up in a reasonable amount of time.  They also stacked their monsters with a lot more mechanical complexity than you're going to find in 5e, with fewer hit points and a higher armor class.

One-to-one swaps get harder and harder the higher level the party gets.

Quote from: Socratic-DM on December 10, 2023, 01:35:25 PM
This is a not a question about what is the OSR

That is the soul of the question, actually. I can easily say what I would call OSR-compatible: monster stat blocks that put inline an AC or Defense, HD, hit points, attacks, move, etc., with number values that exist somewhere in the Basic D&D to AD&D 2e continuum. It's the sort of thing we would heedlessly mash together, across multiple editions, across incompatible expansion materials and the perilous D&D/AD&D divide. Like how B4 duplicated some monster stat blocks because of the differences in the example monsters between Basic, and Other Basic.

But if you mean any game that's compatible with another OSR game, well. Runequest? DC Heroes? Top Secret? What about Top Secret S.I.? At that point, when you say compatible, what are you meaning you intend to do with it?

Or are you asking, essentially, if a game has to have certain requirements to be an OSR game, and that is what you mean by compatibility?

To clarify.

OSR has at least three meanings:

- Compatible with TSR-era D&D (even vaguely).
- Inspired by older RPGs, usually pre-1990 (an immense group of games).
- Adopting design principles valued by modern OSR circles, NOT necessarily present in TSR-era D&D (eg. rulings, simplicity, etc.)

So, a game can be called "OSR" and STILL not be compatible (although I feel any classification that puts D&D, WFRP, Runequest and Traveller in the same category to be nearly useless).

Quote from: Eric Diaz on December 11, 2023, 07:45:10 PM
To clarify.

OSR has at least three meanings:

- Compatible with TSR-era D&D (even vaguely).
- Inspired by older RPGs, usually pre-1990 (an immense group of games).
- Adopting design principles valued by modern OSR circles, NOT necessarily present in TSR-era D&D (eg. rulings, simplicity, etc.)

So the label has been stretched to the point of losing any real meaning.

1&2 aren't mutually exclusive, take Pundit's Arrows of Indra, it's not a straight retroclone with different races/classes, yet you can import those races, classes and monsters to any OSR (the real one) game with little to zero conversion needed.

White Box FMAG departs from TSR-era D&D in a few points, yet you can use adventures from those golden years with it with almost zero work, same goes for the games based on it or OSE and the games based on it.

Quote from: GeekyBugle on December 11, 2023, 07:53:55 PM

Quote from: Eric Diaz on December 11, 2023, 07:45:10 PM
To clarify.

OSR has at least three meanings:

- Compatible with TSR-era D&D (even vaguely).
- Inspired by older RPGs, usually pre-1990 (an immense group of games).
- Adopting design principles valued by modern OSR circles, NOT necessarily present in TSR-era D&D (eg. rulings, simplicity, etc.)

So the label has been stretched to the point of losing any real meaning.

1&2 aren't mutually exclusive, take Pundit's Arrows of Indra, it's not a straight retroclone with different races/classes, yet you can import those races, classes and monsters to any OSR (the real one) game with little to zero conversion needed.

White Box FMAG departs from TSR-era D&D in a few points, yet you can use adventures from those golden years with it with almost zero work, same goes for the games based on it or OSE and the games based on it.

Yes, exactly.

1 is the narrowest (and most useful IMO).

2 & 3 are so wide that they become almost meaningless. Anything can be "inspired" by old games, there are so many of them. Likewise, even Risus (a modern game) uses rules, simplicity, etc.

A game like White Box FMAG probably can be included in the three groups, but what really matters, like you said, is that you can "use adventures from those golden years with it with almost zero work".

Of course, there are shades of gray. LotFP is certainly OSR in this narrow sense, DCC is stretching it a bit, Mork Borg is "OSR-inspired" and not exactly OSR, IMO (from a brief read).

I should add that the term OSR was created in the 2000s, so T&T and Arcanum are "OS" but not "OSR".