Build your first system in Grimoire

Grimoire does not ship with your game. It ships with a way to describe it. You tell it what a character is made of, and the sheet, the dice and the campaign screens follow. This guide walks through that once, with a small made-up game, so you know what each part of the editor is for before you sit down with the rulebook you actually play.

If you would rather start from something that already works, the app offers three ready-made systems on first launch: one for tables that roll a single die and add a bonus, one for pools of dice counted for successes, and one for percentile rolls under a rating. Pick the closest, rename what needs renaming, and skip to whichever section below you get stuck on.

Before you type anything

Open the rulebook to the character sheet and answer four questions on paper:

1. What are the base numbers? The three to eight stats everything else is built on. Strength, Agility, Mind — the ones you roll or add.
2. What is trained? The skills, and which base number each one sits under.
3. What is calculated? Anything the sheet works out from other numbers: defence, carrying capacity, hit points at first level.
4. What goes up and down during play? Wounds taken, points spent, spell slots left.

Almost every game, from a 1970s dungeon crawl to something published last month, fits in those four boxes. The editor has one section for each, plus two for the lists (weapons, talents, spells) and one for the dice.

Open the editor

From the home screen, Game systems → Build from nothing. Give it a name and a colour. The colour is not decoration: every campaign and sheet built on this system carries it, which is how you tell two tables apart at a glance.

The Tier section is a single number for "how far along a character is": level, rank, experience grade. If your game has none, set it to 1–1 and forget it. Formulas can use it, which is why it exists.

Attributes

Add each base number with a name, an abbreviation, a minimum, a maximum and a starting value. The starting value is what a new character gets before anybody spends points, so put the game's baseline there, not zero.

For our made-up game: Body, Wits and Nerve, 1 to 5, starting at 2.

Tapping an attribute on a sheet rolls it. What that roll means is decided later, in Dice rules, so do not worry about it yet.

Skills

Each skill is filed under an attribute. That link is what the roll uses: a game that rolls "attribute + skill" needs to know which attribute, and a game that rolls the skill alone still uses it to group the sheet.

Ours: Fight and Climb under Body, Notice and Lore under Wits, Talk and Sneak under Nerve. 0 to 3, starting at 0.

Derived stats

This is where a spreadsheet would normally come in. Instead, write a formula in the game's own words:

defence  =  nerve + 2 + armour
carry    =  body * 5

The variables are the keys of what you have already defined — the editor lists them under the field — plus tier, plus anything a sheet section feeds in (more on armour in a moment). floor, ceil, max and min work, so ceil((wits + notice) / 2) is fine.

Derived stats are never typed in and never saved. They are recomputed whenever anything they depend on changes, including bonuses from gear. If a number on the sheet can be worked out from other numbers, put it here, not in Attributes.

Resources

Anything that moves during play. Each one is either a bar that fills up towards a maximum (wounds, stress) or a number only that gets spent and replenished (hero points, ammo, energy).

A bar takes a maximum formula: body + 5 for Wounds. A number takes an optional starting formula: tier for Luck. Set the scope to Party for something the whole table shares — a momentum pool, a doom counter — and it lives on the campaign screen instead of on any one sheet.

Sheet sections

The lists. Weapons, armour, gear, talents, spells, injuries: you decide which sections exist and what a single entry in each records.

Start with three:

• Weapons with fields Rolls (text), Bonus (number), Damage (text). Under the section's settings, choose Rolls for Rolls listed in and Bonus for Added to that roll: each weapon becomes a button that rolls the skill you picked for it, with its bonus added. Damage stays text — it lands on somebody else, and the app does not make rules calls about the target.
• Armour with a field Rating (number). Turn on Equippable, set Whole section adds to to armour and Taking the number from to Rating. Now defence = nerve + 2 + armour reads the equipped suit. Take it off and Defence drops.
• Talents, with just a description. Turn on Entries can grant bonuses if a talent can say "+1 Body": each entry then names what it adds, and the bonus reaches the formulas and the rolls.

The rule of thumb: the app computes what touches your own roll, and you read and apply what touches the target.

Dice rules

One picker does most of the work: How a roll works.

• A pool of dice — Body 3 with Fight 2 rolls five dice, and each die is read against thresholds you set (a 5 or 6 is a success, say).
• One die, plus your rating — the d20 family. Roll one die, add the numbers.
• Roll under your rating — the percentile family. The rating is the target; succeed by rolling at or below it.

Pick one and the die type, and the rest — thresholds, a special die, rerolls, exploding dice, keep-highest — sits under Advanced for the games that need it. Every roll on the sheet shows its breakdown afterwards: which dice, which bonus came from which item. If a number on the roll screen surprises you, the answer is on the same screen.

Our game: a pool of d6, 5+ is a success.

Make a character and check

Save, start a game on the new system, create a character. Then do three things:

1. Change an attribute and watch the derived stats move.
2. Add a suit of armour, equip it, unequip it. Defence should change twice.
3. Tap a skill and read the roll screen. The dice count should be attribute plus skill, and nothing else — unless a talent says otherwise, in which case it should say so on the screen.

If any of those is wrong, the mistake is in a formula or in a section's bonus settings, and the editor is where to fix it. The sheet will follow.

Share it

Once it works, Game systems → the ⋮ menu on your system → Share with players produces one file with the rules and the catalogue of gear you have built. Your players import that file on first launch and are ready to make a character. When you fix a formula later, share again; when you only add gear, the catalogue can be sent on its own from the library screen.

That is the whole loop: describe once, play on it, correct what the table finds. The rulebook stays on the shelf.