The tenets of the old school revival (or renaissance) are best summarized in the Principia Apocrypha by Ben Milton and Steve Lumpkin. These tenets prevail in old school games, some of which are considered retroclones (faithful reproductions of D&D 2e and earlier editions) and some of which are considered old-school adjacent (inspired by the tenets of old school play, but not necessarily compatible with D&D 2e and earlier games).
In the Principia Apocrypha, the old school style is defined as follows:
"The more of the following a campaign has, the more old school it is: high lethality, an open world, a lack of pre-written plot, an emphasis on creative problem solving, an exploration-centered reward system (usually XP for treasure), a disregard for "encounter balance," and the use of random tables to generate world elements that surprise both players and referees. Also, a strong do-it-yourself attitude and a willingness to share your work and use the creativity of others in your game."
As an old-school adjacent game, OSR+ shares much in common with this philosophy, but not everything. Because the purpose of play in OSR+ is narrative fulfillment, the system departs from the philosophy in a number of important ways. In this section we look at both the "Yes, And" and the "No, But" of OSR+ with respect to these principles, to see how the game aligns and disagrees with the tradition from which it takes its name.
The Yes, And
A disregard for encounter balance
DEADLY But Avoidable Combat
COmbat as War, Not Sport
Learn When to Run
Don't expect encounters to be "balanced." […] Combat in old school RPGs is often neither balanced nor fair, and PCs should encounter foes far more powerful and numerous than they are […] Old school adventures often present deadly encounters that, to the eye of a modern gamer, may seem like you're expected to beat them […] Encourage the players to outsmart and outplan their enemies if they want to survive […] Potentially deadly combat is a common problem, one which should encourage solving in a variety of ways other than head on.
Insofar as encounter design goes, the worlds of OSR+ don't care if you're a good match for them, and so players need to make smart decisions if they want their heroes to survive. This is underscored by the low HP and high lethality of the combat mechanics. While it's true that it is possible to design "balanced" encounters in OSR+, you shouldn't feel obligated to do so if it doesn't make sense for the fiction (e.g., if your players wander into the Emperor's throne room, they face the Emperor and his retinue in all their high-level glory).
That being said, OSR+ isn't as punishing as other old school games when it comes to death and dying. Yes, things can go south very quickly for players in combat, but several metacurrencies exist in the game that allow them to seize control of the narrative when the dice fail them: namely, fate points and story tags. If you want to raise the stakes in the adventure, you must use attrition against the players to whittle down these metacurrencies.
The system is designed to be balanced when designing heroes, however. During character creation, the system ensures that all heroes are equally powerful at 1st level, so that no one character concept is mechanically preferable to another.
Rulings Over Rules
The primeval old school principle. Old school style games are often sparse in what situations their rules cover. They are often minimal, or no "skills" or "feats." This is a feature, not a bug.
The intent of all mechanics in OSR+ is to provide a toolkit for the GM to referee uncertain outcomes.
A cardinal rule of the old school style is avoid mechanics that can be "pushed" like a button on their character sheet to solve problems in the fiction: usually, this means there are no feats nor skills baked into the rules, so players are forced to be creative in what they try to do.
While OSR+ has skills, the mechanic only imparts a bonus to certain actions players can take that happen to align with the skills they have. Outside of this, heroes have very few other defined abilities (a class, kit, and origin ability, for example). Moreover, the rules in OSR+ are written in such a way to allow the GM room to make fiat decisions, based on common sense, when the rules as written don't speak to a particular context.
LEAVE PREPARATION FLEXIBLE
Build Responsive Situations
Let them Off the Rails
Don't prepare a plot for the players to follow [...] Keep your situational ideas loose enough so they can be adapted to the PC's choices and the flow of the game [...] The direction of the game should be guided by the players' decisions, not the GM's [...] Establish situations with several actors or factions are pursuing their own ends. Let the players' actions affect this environmnet, and let the consequences affect the players in turn [...] Feel free to let them know where most of your prep is, but if you expect them to zig and zag, don't constrain or re-route them. If you don't know what comes next, let random tables fill in the blanks, then build on it between sessions. Find the excitement they see and embrace, too, the chaos of the players.
Adventures in OSR+ are minimalistic on purpose. They focus on providing a living sandbox within which scenes and adventure hooks can be rearranged or re-purposed by the GM depending on what players do in the fiction. In this way, players generate the "plot" by bouncing from one scene to another, which allows you to react to the evolving narrative, rather than prescribe it.
This approach to designing adventures with minimal prep is reinforced in the system by keeping the rules themselves brief (no more than a few sentences per mechanic) and providing NPC shorthand to construct encounters quickly.
Embrace Chaos... But Uphold Logic
Subvert their Expectations
External inspiration and random results help you divest yourself or [your players'] fate. Use random tables to keep the game fresh [...] but don't use random results to the extent the world feels nonsensical [...] It's inevitable that players will have knowledge about common fantasy elements from pop culture. Inject common monsters, locations, and situations with your own unique twists; surprise them.
Respecting where the dice fall strengthens the versimilitude of the game world, which should be as unpredictable and harsh as the real world. Accordingly, the rules of OSR+ take a simulationist approach to the fiction, and common sense rulings should always follow from the context of the fiction.
Offer Tough Choices
Keep Up the Pressure
Make the players weigh risk versus reward [...] The greatest treasures are always the hardest to reach. Risk and reward are also at the heart of combat [...] Look for situations where all obvious choices come with a heavy cost. These situations encourage unorthodox solutions and lateral thinking [...] Keep the players desperate and on a clock. Maintain a tension between the desire to explore and loot, and the terror of remaining too long. If the players repeat attempts at a challenge [...] give them a consequence.
Part of what this principle speaks to is attrition, even if OSR+ is not concerned with the specific activities of dungeon crawling (exploring and looting).
In OSR+, players carry a metacurrency that helps them control the narrative in the form of fate points and story tags. While most OSR+ games don't involve dungeon crawling, the idea that the farther they get into the adventure, the more difficult things becomes still holds true, and in order to increase the danger in an OSR+ game, you need to whittle down their control over the narrative by divesting them of fate points and story tags.
In the context of OSR+ games, the notion that we need to "keep up the pressure" translates to keeping the players moving between scenes, which in turn equates to driving the narrative forward. Clocks are one way to do this, even if the peril they face isn't violence.
Don't Be Limited By Your Character Sheet
Rules and mechanics are only triggered by what happens as established in the conversational fiction of play. To do something, describe your character doing it; if you need to roll dice, the GM will let you know. When presented with a problem, don't expect to "use" your character's skills or abilities on it.
The idea that manual interrogation of the fiction is what triggers mechanics (as mediated by the GM) is absolutely central to the way an OSR+ game is played, and this principle underscores both old school and PbtA styles of play.
Cleverness Rewarded, Not Thwarted
Clever solutions to a problem should usually work, as long as they are within the realm of possibility. Be generous [...] Strongly reward even slightly creative solutions. One of your goals as a GM is to encourage this mentality [...] Give them the benefit of the doubt when they've worked to give themselves the upper hand in the fiction.
This advice gels with the general sentiment that the GM should be a fan of his players' characters in OSR+, not a neutral arbiter (despite that this is at odds with the old school style). Furthermore, the GM can reward players with fate points when they come up with creative solutions to problems in the fiction. Fate points allow players to take control of the narrative, which in turn allows them to come up with more creative solutions to problems.
For some old school players, however, the ability to collaborate with the GM to create aspects of the world (via narrative advantage) is an anathema to the simulation. As an OSR+ GM, however, you should encourage players to collaborate on the worldbuilding, whether through downtime, narrative advantage, or other actions that invite such collaboration on the fiction, as it increases their investment in the world at large by extending to them ownership over it.
Good Items are Unique Tools
A good tool doesn't (only) increase PCs' damage or add an ability bonus, it does an odd, very specific thing that is only powerful when used cleverly. This turns every problem into a puzzle and encourages creative solutions.
This sentiment is expressed in OSR+ through the way treasures, spells, and weapons are designed. You will find that treasures never add modifiers to rolls or improve damage; spells never directly cause damage and only rarely impact rolls; and the primary differentiator between weapon classes besides the damage they do is their tactic, which enhances the sort of maneuvers player might invent when engaging in combat.
Reveal the Situation
Give Them Layers to Peel
Don't Bury the LeDE
Keep the World Alive
NPCS aren't Scripts
Don't hide important information from the players. Apply real-world logic to populations and challenges, rather than building carefully balance sequence of fights. Assume the characters have common sense [...] Create layers of information for the players to peel back and explore. Your details should allow players to make informed decisions and take action [...] Let unknown mysteries become known problems [...] Tie lore and mysteries into treasure that the players already want to acquire [...] Treat NPCs like real people: think about what NPCs want, especially in combat.
Thinking about the fiction as a living, breathing microcosm that exists to be manually interrogated by the players is central to how OSR+ functions as a game. All of the advice here in the Principia Apocrypha is pure gold, and speaks for itself.
One caveat: while NPCs in OSR+ don't have a morale mechanic or reaction roll to test against, the advice that NPCs aren't video game characters who fight to the death is important to keep in mind. You can test their mettle with simple opposed Influence checks when the going gets tough for their side.
And as far as tying lore and mysteries to treasure, however, the story hooks players create in session zero are, in many ways, the "treasure" they haul back to advance their characters. You want to tie lore and mysteries to these story hooks, so players feel invested in the world and want to explore it.
Ask Them How They Do It
Scrutinize the World, Interrogate the Fiction
The Only Dead End is Death
LET THEM MANIPULATE THE WORLD
Encourage players to interrogate the fiction "manually," asking them to describe the manner in which they interact, rather than eliding their actions via a roll or assumed character ability [...] [Players must] describe the real actions [they] take to achieve the effect [they're] looking for [...] Remember, other games may have dice rolls to do this for you—many old school games don't, so engage! [...] Often, digging into the fiction and engaging the world as real will open up new and unexpected avenues [...] The focus of the game should be on creative problem solving, not brute force, so give players tools to make that appealing.
The presence of skills in OSR+ might seem like "dice rolls [that] do this for you," but skills in OSR+ aren’t substitutes for manually interrogating the fiction: players apply skills to actions they take in order to increase the chances of turning up more clues (for example, when searching a room or disarming a trap). A player always begins the conversation with describing what they do, not what mechanic they want to use to solve the problem at hand. Only if their interaction requires a roll does the GM ask for it, and only then can the player add a skill if it's relevant to the roll.
As the old school style prescribes, continually interrogating the fiction is the way to advance the narrative: "Couldn't pick up that door? Maybe one of those unidentified potions will help ... That dead-end hallway may hide a secret door, or maybe there's another passage to investigate." A failed roll then is merely an opportunity to try something else. And in other situations (as is the case with a success check), the check itself yields new opportunities, which the player can choose to pursue as the fiction evolves.
The No, But
On Dungeon Crawling
OSR+ is not designed for dungeon crawling or hex-crawling adventures in particular (although The Great White North campaign setting takes a generative approach to that sort of play style). Consequently, there is no love for inventory tracking or death by attrition in the core rules.
OSR+ is an OSR-adjacent game, not a retroclone, and is not at all compatible with D&D.
XP for Diversity & Adversity
Many old school style games directly correlate XP earned with the value of treasure returned to safety. This is a convenient abstraction of the characters learning from the exploration and adversity of retrieving the treasure.
Gaining experience in OSR+ is triggered by fulfilling story hooks or completing a certain number of sessions up to GM fiat, not by killing monsters or collecting treasure and exchanging it for XP. However, the "abstraction" that XP for treasure represents is parallel to players exploring scenes in order to find and complete their story hooks (which is only rarely about defeating monsters).
Moreover, on a mechanical level, OSR+ encourages avoiding combat and using ingenuity to get out of dangerous situations because of how few HP heroes have relative to the perils they face.
Player Ingenuity Over Character Ability
Don't Mind the Fourth Wall
Build Challenges with Multiple Answers
And Challenges with No Answer
Players are not meant to solve problems with dice rolls, but with their own ingenuity. Therefore, present them with problems that don't require obscure knowledge, have no simple solution, but have many difficult solutions [...] Avoid singular chokepoints to progress. Give them obvious, equally, but differently-difficult alternatives [...] Trust in your players. Let them surprise you and find answers to problems that you couldn't expect, and can't help them with [...] Don't worry much about "metagaming" or the dissonance between what the players know and what the characters know. Favor the ingenuity of the players over strict personification of their characters [...] Don't worry too much about low stats, or roleplaying to match them.
The old school style promotes the idea that players should make decisions as they would, not as their characters would. In OSR+, however, players should fully their inhabit their heroes when they adopt their roles, down their personification and decision-making ability. This means it's important to maintain that fourth wall between player knowledge and character knowledge, even if it's to the hero's detriment when they take action in the fiction.
When it comes to designing challenges, we want players to come up with clever solutions, so you don't want to design challenges with a single solution in mind. As the Principia Apocrypha notes, it's also OK if you have no solution in mind, with one caveat: mysteries. Mysteries with no pre-determined solution become goose chases that undermine the spirit of exploration and render clues meaningless: While there are games like Brindlewood Bay that do this—a cozy murder mystery RPG that generates a mystery on the fly—the key difference is that when players play Brindlewood Bay, they sign up for a game where the mystery is generative, knowing that the solution to the mystery will be collaboratively arrived at during the course of play. OSR+ and other games in the old school style are simulationist in nature, which means the play expectation is that most things exist out in the fiction to be discovered and manually interrogated (such as clues). Thus players expect a solution to the mystery to pre-exist, and to generate one on the fly goes against this expectation. there is no point for players to look for clues if the clues don't point to anything pre-existing in the end.
Furthermore, when players take advantage of the "gaps" in the rules, the GM should reward them for their out-of-box thinking by translating their ingenuity into mechanical advantage.
LET THE DICE KILL THEM
BUT TELEGRAPH LETHALITY
LIVE YOUR BACKSTORY
Don't put too much work into a backstory for your characters [...] Protecting the PCs from death can result in games that lack tension and players who only solve problems with brute force [...] Unambiguous character death gives weight to both the risks and rewards of play. Character creation is simple and quick in these games for a reason [...] Give players the chance to think their way around threats and obstacles by telegraphing them ahead of time.
In session zero, players develop their heroes' backstories in order to create a stake in the world and create the world itself, collaboratively. Session zero functions as a springboard into action and sets the "win condition" of the game for each player (what they must do to resolve their heroes' conflict). It's important for the GM to be a fan of his players' characters (rather than simply a neutral arbiter of the game) in order to enable them to engage with their story hooks through the course of the adventure.
Because we invest a lot of time into session zero at the outset of the adventure, OSR+ departs from the old school style with regard to PC death. There are no mechanics for one-hit kills (inclusive of fatal peril), and the system provides multiple options for characters to take control of the narrative to escape death, both through the use of fate points and the death's door mechanic.
Power is Earned, Heroism Proven
Unlike many modern RPGs, your character starts with little power. Your meager means and abilities at first level encourage lateral thinking to get you out of trouble.
While characters don't start off as superheroes in OSR+ per se (which is a criticism levied against modern traditional RPGs like Dungeons & Dragons Fifth Edition), they do start off as heroes, and will be about as powerful as they can be for the rest of the campaign, at level 1. This is in stark contrast to the old school style, which positions characters as expendable blank slates that need to earn their keep by surviving through brutal starting conditions.
In OSR+, experience gained after level 1 only incrementally improves heroes' abiities, and there are only 10 levels of advancement possible (each level only affording a hero a single incremental improvement). This means that the power differential between a 10th level character and a 1st level character isn't an immense gulf as it is in other modern, traditional games. A 10th level character can be just as vulnerable as a 1st level character in OSR+, especially if the PCs employ the right tactics at the right time, and engage the enemy smartly.
Divest Yourself of Their Fate
Portray the world and embody its denizens genuinely, as they would react to the characters' behavior. Don't set out to tell a story, let one emerge from the character interactions with the world.
While the GM should mostly function as a neutral referee with respect to rendering rulings in OSR+, he must also incorporate the story hooks that the players created in session zero into the game world, in order to provide opportunities for players to resolve their heroes' conflicts. This is at odds with the old school style, which generally instructs the GM not to "author" the narrative in any way.
Although the OSR+ GM must to plant these seeds of destiny into the adventure, he always respects the dice where they fall: Never fudge a roll, and always roll in the open.
Play to Win, Savor Loss
Learn to love the disgusting, horrifying, shocking, surprising, and even disappointing ways your characters are set back. And remember, through play, a story emerges larger than any one character. You will make your mark on the world, be it an unknowingly misleading arrow scratched into a dungeon wall, or a crater where a city once stood.
Make no mistake: OSR+ is a simulationist RPG, and most of its mechanics enable narratives to arise in an emergent sort of way (i.e., most mechanics are diegetic and simulate things heroes do in the fiction, as opposed to things players do outside the fiction to direct the narrative). However, the goal of play in OSR+ is narrative fulfillment, which is a goal fundamentally at odds with the old school style. This is the “win” condition for a player: to resolve the conflict they built into the hero during session zero. This requires the GM to insert story hooks into the adventure, so the players' can fulfill their heroes' destinies.
In the old school style, no one makes assumptions about where the narrative will end up when they first set off on their adventure: if you start the game as a disgraced queen looking to restore her kingdom to power, you might end up as a murderous drunken pirate on the high seas by the campaign's end. Nobody knows what will happen. But in OSR+, you play a disgraced queen because you want to restore your kingdom to power, and you create story hooks so the GM can make that possible during the course of the adventure.
Now this doesn't mean you won't end up as a murderous drunken pirate in the end—after all, it's possible that to resolve your conflict, you must fail to resolve it, which results in the retiring (or death) of your character. Who knows? The key difference is that you're playing the game with the expectation that you will engage with the narrative "I will try to restore my kingdom to power" at some point during the adventure, and the GM will create opportunities for that engagement to happen.