a ruby DSL for games typically played without a computer
Switch branches/tags
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.



Build Status Code Climate

Tabletop aims to provide a simple way of describing, automating and tracking the tools and tasks involved in "analog" games, determining results from the motions and properties of various dice and chips.


gem install tabletop

require 'tabletop'


For detailed information, I recommend the full documentation, but I want this file to give you a good primer, so let's get started.


Dice are pretty straightforward. They've got a number of sides, set on instantiation (defaulting to 6), and a current value between that number and 1 inclusive, which can be set on instantiation, or set directly. Finally, they can be rolled, which gives them a new random value.

d6 = Die.new
d6.sides     #=> 6
d6.value     #=> 4
d6.value     #=> 2

d8 = Die.new(8, 4)
d8.sides     #=> 8
d8.to_s      #=> "[4]/d8"

One fun special kind of die is a "Fudge Die". They are a special kind of three-sided die that have three possible values: -1, 0, or 1. Those are usually expressed as '-', ' ' and '+', though.

f = FudgeDie.new
f.sides      #=> 3
f.value      #=> 0
f.to_s       #=> "[ ]"

You may not believe this, but coins are also a special case of die. Coins have two sides, and have a value of either 1 or 0, aka heads or tails, aka "+" or " ". They can be rolled if you really want, but you'd normally call that "flipping," right?

c = Coin.new
c.sides      #=> 2
c.value      #=> 1
c.to_s       #=> "(+)"
c.flip.to_s  #=> "( )"  


Pools are arrays of Dice objects with some extra helpful methods.

Tabletop ships with a monkeypatch to fixnum that enables an easy way to build pools with d-notation. It's not loaded automatically, but you can easily enable it.

require 'tabletop/d_notation'
3.d6           #=> [[3]/d6, [3]/d6, [4]/d6]
2.d10 + 1.d8   #=> [[2]/d10, [6]/d10, [8]/d8]

You can also create pools by passing Pool.new a literal array of dice, or (slightly more interesting) a string in die notation.

Pool's instance methods are common operations you might do on a pool of dice: summing, counting sets, dropping the lowest or highest valued dice, dropping all but the lowest or highest valued dice, even dropping any dice a specified list of values.

d&d = 3.d6.sum    #=> 13
ore = 10.d10.sets #=> ["3x2", "2x8", "1x7", "1x6", "1x4", "1x3", "1x1"]
cortex = (1.d8 + 2.d6).drop([1]).highest(2).sum  #=> 9
tsoy = (4.dF).drop_lowest.sum  #=> 2

You can also #roll an entire pool, or you can interact with individual dice in the array using array indices ([]).

When pools are compared to each other or to numbers with <=>, it's assumed you're actually interested in their sum. The same thing happens if you try to add a number to them.

4.d4 + 4         #=> 17
1.d20 > 2.d10    #=> false


Rolls are very much under construction and their API is in flux, but they allow you to automate randomly determining results in a variety of ways.

Rolls have a lot of options, described in detail in the documentation. But let's take a simple example from one of my favorite games, Apocalypse World.

When you open your brain to the world’s psychic maelstrom, roll+weird. On a hit, the MC will tell you something new and interesting about the current situation, and might ask you a question or two; answer them. On a 10+, the MC will give you good detail. On a 7–9, the MC will give you an impression.

(In the parlance of the game, a "hit" is getting a 7 or higher. "Roll+weird" means to roll 2d6 and add the character's "weird" stat, which is an integer from -1 to 3.)

Here's how I'd write that out in Tabletop:

weird = [-1, 0, 1, 2, 3].sample #=> get a random stat

open_brain = Roll.new(2.d6) {
  add weird
  at_least 7, "the MC will tell you something new and interesting about the current situation..."
  equals (7..9), "...but it's just an impression"
  at_least 10, "...and it's a good detail"

Simple, right? add sets a value to be permanently added for the purposes of determining results. at_least and equals take an integer (or a range, in the case of equals) as their first parameter, and then one or more values to return if the pool's result meets the stated condition.

Once they've been instantiated, Rolls have three important methods.


This method which re-rolls all the dice in the pool, and returns the Roll object. It can take an options hash as a parameter. Notably, one of the options is :modifier, which sets a temporary modifier for that roll only; it's cleared the next time roll is called.

bad_luck = -1
open_brain.roll(:modifier => bad_luck)


This method, by default, returns the sum of the values of the Roll's dice, plus any static modifiers from add or per-roll modifiers from roll(:modifier).

But! When instantiating a roll, you can call set_result with an appropriate symbol to make result mean something else.

For example, in Exalted, you principally care about how many dice in your pool came up 7 or higher, counting 10s twice:

exalted = Roll.new(8.d10) do
  set_result :count, :at_least=>7, :doubles=>10

exalted.result   #=> 2
exalted.sum      #=> 30


This method returns either an array containing the results passed to any at_least and equals calls whose conditions were met, or nil if no such conditions were met.

So, possible results for our cool AW roll:

open_brain.roll.effects #=> nil
open_brain.roll.effects #=> ["the MC will tell you something new and interesting about the current situation", "...but it's just an impression"]
puts open_brain.result  #=> 10 
puts open_brain.effects #=> ["the MC will tell you something new and interesting about the current situation", "...and it's a good detail"]


Decks are essentially weighted hashes with a random #draw method. You can put whatever hashable object you like in a deck (there's no Card class yet) as a key to a value that indicates the number of copies of that object in the deck.


This method returns another deck, and reduces the number of cards in the original deck appropriately.

  d = Deck.new
  d["card A"] = 20
  d["card B"] = 19
  d.deck_size      #=> 39
  hand = d.draw(3) #=> {"card A"=>1, "card B" =>2}
  d                #=> {"card A" => 19, "card B"=>17}
  d << hand        #=> {"card A" => 20, "card B"=>19}

Coming Soon

That's already enough functionality to do many different kinds of rolls, but there's a lot more in store.

One bonus thing I'll briefly note is that Rolls can be nested, and effects returns them as such.

rps = Roll.new(1.d3) {
  equals 1, "rock"
  equals 2, "paper"
  equals 3, "scissors"
jkp = Roll.new(1.d3) {
  equals 1, "guu"
  equals 2, "choki"
  equals 3, "paa"
fist_game = Roll.new(1.d2) {
  equals 1, "Rock Paper Scissors", rps
  equals 2, "JanKenPon", jkp 
fist_game.roll.effects   #=> ["JanKenPon", ["guu"]]

This can lead to some surprisingly sophisticated constructions. Remember that "tables" are really just a special case of a roll!

How to contribute

First and most importantly, if you're reading this and you make games, please tell me about them! Second, any complaints or suggestions are always welcome, regardless of coding knowledge. Feel free to communicate your opinions by creating an issue on github, or just dropping me a line at nick.novitski@gmail.com.

If you have clear ideas about what more the project should do, and you think you can do something about it, then make it so! Don't even bother asking me about it, you know the drill:

  • Fork the project.
  • Create a topic branch.
  • Make tests that describe your feature addition or bug fix.
  • Write code that passes those tests.
  • Send me a pull request.


Copyright (c) 2011 Nick Novitski. See LICENSE for details.