za3k > games > logic potions

playtesting: ok, but the same every game

a logic game for 2-4 players about brewing potions. players are gradually eliminated by LOSING. the last player standing wins. how long it takes per turn depends entirely on your group. a game is not many turns. if you like zendo, mao, or nomic, you may like this game.

i recommend checking out the faster and/or simpler variants immediately before first play.

materials: a deck of cards or a lot of skittles; a piece of paper and a pencil

written by zachary "za3k" vance on 2021-03-13.


the players take turns combining ingredients to brew potions, and inventing rules about what happens when you combine ingredients. there are difficult logic goals for each half of the game. if you violate any of these six goals, you have not violated the rules of the game. however, the other players have the opportunity to call you out and make you immediately LOSE, if and when they catch you violating a goal.

first, you want to brew potions. to brew a potion, you combine ingredients and declare what potion type you get.

second, you make Rules about how potion brewing works.

for each goal, if a player violates the goal, you can call them out using the game rule in parentheses. whenever you call someone out, it's a deathmatch--one of you will LOSE.

play area and concepts

  1. Ingredients
  2. Potions List
  3. Rules
  4. Brewing


Example Rules

What are rules?


Each player takes turn being the active player. On their turn, the active player does the following in order. A player can always choose to LOSE and end their turn early.

  1. The active player may optionally challenge an existing Rule, see below. They can issue any number of challenges, but each is resolved separately.
  2. The active player selects 1-3 ingredients from their hand to brew. The goals of brews are given in "Overview" above.
    1. They wait for the other players to PREDICT. Any player other than the active player may PREDICT (but only one player). Whoever calls it first gets it. If no one wants to predict, play proceeds normally. You can use a timer, go around in a circle and have each player PREDICT or pass, or just informally ask "Anyone want to predict?".
    2. To PREDICT, another player says aloud out what potion type they know it will make. They should be 100% sure--this is for when you can 100% deduce the answer, not just guess.
    3. The active player brews together their ingredients and announces the result from the potion list. The result can be any potion type.
    4. Any player can say "ILLEGAL" if they think the brew violates a Rule. They point at the brew and any Rule. Again, if all players pass or a timer runs out, play proceeds.
      • If the brew and the Rule are compatible, the player who said "ILLEGAL" LOSES, because they were wrong and the brew was legal.
      • If the brew and the Rule are incompatible, the active player LOSES for violating that Rule.
    5. If there was a prediction
      • If the active player brewed what was PREDICTED, the active player has been successfully PREDICTED and LOSES immediately.
      • If the active player brews anything else, the predicting player failed, so they LOSE.
    6. The brew is complete.
  3. The player makes up a Rule which would make the brew they just did illegal, and writes it into the rulebook.
    1. A Rule can be anything allowable in the right format. It should be short, clear and readable. The goals of rules are given in "Overview" above.
    2. Any player can say "STILL LEGAL" if they think the current brew is still legal under the new rule. They point to the brew and the new Rule. Again, if all players pass or a timer runs out, play proceeds.
      • If the brew and the Rule are compatible, the active player LOSES for failing to make the brew illegal under the new Rule.
      • If the brew and the Rule are incompatible, the player who said "STILL LEGAL" LOSES, because they were wrong and the brew is illegal now.
  4. The active player "drinks" the brewed potion, discarding the brew ingredients.
  5. The active player takes 2 ingredients from the market and adds them to their hand.
  6. The active player draws replacement ingredients for the market, bringing it back up to 4 ingredients.


IF-THEN logic primer

Example Rules

In Logic Potions, a brew and a Rule can be compatible or incompatible. You will never need to determine if two Rules are compatible with each other, only a brew and a Rule.

  1. If the IF part is false, the brew result and the Rule are compatible.
  2. If the THEN part is true, the brew result and the Rule are compatible.
  3. Otherwise, the brew result is always incompatible with the Rule. Also, the IF part is true and THEN part is false.

challenging rules

On their turn, a player can challenge a Rule as being invalid in some way.

  1. The person issuing the challenge is called the challenger.
  2. There are two kinds of challenge: Contradiction or Universal Theory. Some extra types are provided in "Variants" if you get bored.
  3. The challenger names the challenge type, and Rule number being challenged. ex. "Rule 10 is invalid, I issue a Contradiction Challenge."
  4. During a challenge, slide a piece of blank paper to cover all higher-numbered rules. Ex. if Rule 10 is challenged, rules 1-10 remain visible, while rules 11 and above are covered and not visible. Later rules aren't used during a challenge.
  5. The author's initials are recorded by each Rule. The author of the challenged Rule must defend against the challenge. You can't challenge your own Rule.
  6. If they author fails the challenge, they LOSE. If they pass the challenge, the challenger LOSES instead.
  7. The author or challenger may give up halfway through the challenge and voluntarily LOSE, to save time.

The challenges are all 100% legitimate. That is, if the challenger is correct, they can 100% always win (if they play correctly). If the challenger is incorrect, the author can 100% always win (if they play correctly). If you don't see why, play a few games or think about it more.

contradiction challenge

A challenger claims the challenged Rule is not logically compatible with earlier Rules, or that it prevents every possible potion result for some set of ingredients.

  1. Thought Experiment: The challenger names a set of 1-3 ingredients (nobody needs to have these ingredients) with a contradictory result.
  2. The author names any potion result. The ingredients and potion result form a brew.
  3. The challenger points to the brew and any visible Rule.

Example Contradictory Rules:

universal theory challenge

A challenger claims the author has completed a Universal Theory of Everything, where the result of every possible brew can be logically deduced. The author must defend.

  1. Thought Experiment: The author names a set of 1-3 ingredients (nobody needs to have these ingredients) they think is not possible to predict using the visible rules.
  2. The challenger names any prediction (which they think is the only possible predicted result).
  3. The author names any other brew result they think is possible, forming a brew.
  4. The challenger points to the brew named and any visible Rule.

Example Univeral Theory Rules:



Whoever makes someone LOSE first wins, and the game is over.


STILL LEGAL is removed from the game, and Redundancy Challenges are added to the game in its place. This means new Rules no longer relate to the brew in any way.

redundancy challenge A challenger claims that a Rule is a logical consequence of earlier Rules (aka is redundant with them, aka can be "deduced" or proven from them). The challenger may quickly explain why, to see if the author agrees and gives up.

  1. Thought Experiment: The author names a set of 1-3 ingredients (nobody needs to have these ingredients). The author also names two potion results C and I. These form brew C (ingredients + result C) and brew I (ingredients + result I). Make sure both players are clear on which is C and which is I.
  2. If the challenger thinks the setup is invalid, they point at either brew and any visible Rule 1-9 (not the final one).
  3. If the challenger thinks BOTH are compatible the Rules 1-10, the challenger points to brew I and to Rule 10 and says "both".
  4. If the challenger thinks NEITHER is compatible with Rules 1-10, the challenger points to brew C and to Rule 10 and says "neither".

emperical potions

This is closer to real empericism (which I like), but it makes the game slower and more think-y (which I don't). This variation also requires the 'mathematical' variant, because Rules must always keep current and past brews legal.

more potions

Rather than having potion types, you have potion adjectives. So you can now brew "a fizzy red potion". I haven't tested this. You could allow IF clauses to refer to adjectives.

passing the buck

potion effects

When you drink each potion type, something happens. Decide what for each type.


Challenging Rules is not allowed at all. Note, this game can end in a deadlock with good players.

victory potions

For a more complicated game. Add a special potion type, a victory potion. If you finish brewing a victory potion (no one STEALS), you drink it. The game is over and you WIN.

If you brew a victory potion, someone else is allowed to shout out STEAL. They name another brew result instead, and take over your brew phase. If they finish brewing, you LOSE. If they LOSE before they finish brewing, you start your brew phase over.



This idea is thematically based on a game my mathematician friends came up with, but which I never played, called "Imaginary Go Fish". That game is written by mathematicians and intended for the same, and is based on formal theorem proving or metamathematics. I replaced theorems by Zendo-style specific examples or counterexamples, in keeping with an original emperical theme I dropped. The main changes from Imaginary Go Fish are the addition of the hand of ingredients, which I think makes the game more appealing and replayable; the gradual elimination of players in place of sudden death, which works better with some careless players; and the simplifications I made to remove 'redundancy' endgame for broad appeal. Also, credit to Zendo and a previous game by myself about regexes for the example/counterexample mechanisms.

For anyone curious, the rules of Mathematical Go Fish were something like: