The Types of OSR Games
While I was learning about OSR games, I created categories to help describe the different kinds of games that can exist in the OSR space. I believe it's an interesting enough idea to update and pull out of the original blog post to simplify sharing.
Original Blog Post (not required reading)
The terms presented here are meant to give new language that can be used to help better clarify what is meant when talking about OSR games. OSR on its own can mean a lot of different things. These categories can help clarify that meaning.
They are not meant to be hard categories. Games may fall under multiples of them. Some games might not fit any of them. This should not be used as a tool to decide what designers should or should not be part of OSR. There's room for everyone.
In general, OSR refers to games that are inspired by or compatible with the TSR era editions of Dungeons & Dragons. This can be done through a variety of strategies, which define their category.
Retro-clones are game which preserve the original rules of RPGs from the 70s and 80s as much as possible. They may update the presentation (layout, improve wording, add clarifications) and provide optional tweaks to improve the gaming experience, but in general they try to preserve the original rules as fully as possible. Rule changes are usually optional or very minor.
Old School Essentials
D&D itself (anything before 3rd Edition)
Retro-updates make small updates to the old rules with modern lessons to make the gameplay more streamlined or fix some perceived quirks. The level of changes could be anywhere from codified house-rules to deeper system changes, as long as the feeling of the original game is preserved.
Such rule changes could include switching descending armor class to ascending, splitting classes and races, changing how experience works, removing level limits, swapping resource, etc.
Dungeon Crawl Classics
Sword & Wizardry
Retro-reimaginings are completely new rules that are still compatible with older content (adventure modules, homebrew, etc). This is generally done by preserving a power level within a certain range of numbers that matches with the older systems, but can also be done through abstractions or re-interpretation of the original materials.
Dungeons of Fate
The Black Hack
The White Hack
The Lavender Hack
Retro-feels are games built with completely new rules which maintain the feeling of playing the original older games, without worrying about preserving compatibility with the older materials. They make take inspiration from the older rules by putting a new spin on it, or provide something entirely different.
Into the Odd
Retro-originals are games which use the old rules to create a new game feel, theme, or experience. They may create new rules to fit those themes, but do so in ways based off of older rules.
Stars Without Numbers
Retro-adjacents (also "OSR-adjacents") are original games with original rules that carry the philosophies of older games into new gaming experiences and genres. They may have little to do with the games that first inspired the OSR movement, but the principles of play are preserved in new designs, keeping OSR ideas alive.
The Mecha Hack