David Donachie's Website

Skip Navigation

GNAT Rules Reference

Welcome to the GNAT adventure system, a rules system for solo adventures that emphasises speed of play and minimal record keeping.

GNAT defines your adventurous character with two numbers: Talent and Vitality. Talent covers both your luck and expertise, while Vitality measures your will to survive and capacity to endure harm.

GNAT requires two six-sided dice.

This reference document is licensed under CC-BY-SA 4.0. You are free to use the GNAT system in your own games, and to produce your own versions of the system, or additional rules material, provided that you give appropriate credit to the original, and abide by the license terms.

Version 1.5

Talent and Vitality

Testing Talent

While playing a GNAT adventure you will frequently be asked to Test your Talent. Roll two dice and comparing the result to your current Talent score; you succeed if the result is less than or equal to your Talent. A natural roll of double 1 (a critical) always succeeds, while a double 6 (a fumble) always fails.

Sometimes you will be supplied with a modifier to the roll, (e.g. Test your Talent at -3). This modifier is applied to your Talent, rather than the dice roll, so a negative number makes it harder to succeed, while a positive number makes it easier.

Occasionally ill-luck or misfortune can result in a loss of Talent, as your will is eroded. In this case you will be told to Lose 1 Talent. Such a loss affects all your tests until you are able to rest, or good-fortune results in you being told to Restore 1 Talent. Restoring Talent will not raise your score above its maximum value.

Being reduced below 2 Talent makes it impossible to succeed on any test, regardless of the roll. Talent cannot fall below 2.

Because the odds of rolling Talent or less on 2d6 form a sharp bell-curve, loss of Talent has little effect on your odds of success when Talent is high, and a large effect when Talent is low. The loss of Talent mechanic can therefore create a terrifying ramp of failure after many wrong choices. Use Talent loss with caution.

Skills

While Talent measures your overall mastery of all areas of life, not every field of endeavour is equal. These areas are covered by Skills, which supply a bonus (+2) to your Talent if you possess them.

If you are asked to (for example) Test Climbing, then you Test your Talent, adding +2 if you have the Climbing Skill. Sometimes you can only make such a test if you possess the skill, at other times you will be allowed to Test your Talent at -2 (a Default Roll). An adventure will tell you when a Default Roll is an option.

A starting character possesses one or more Base Skills, which are ones supplying a +2 bonus, but with experience you may acquire Advanced Skills. Advanced Skills supply a larger bonus, but still give a -2 penalty when you don’t have them. (For more details, see Experience, below).

The basic skill list is: Appraise, Climbing, Diplomacy, Linguistics, Naturalist, Occult, Search, Stealth, Swimming, Tracking, Trapfinding.

  • Climbing: Climbing, balancing, and athletics
  • Diplomacy: Used to negotiate with others
  • Linguistics: Used to translate dead languages
  • Naturalist: Knowledge of plants and animals
  • Occult: The supernatural and spellcasting
  • Search: Used to find hidden things
  • Stealth: Sneaking and hiding
  • Swimming: Used to swim and fight in the water
  • Tracking: Follow trails and find people
  • Trapfinding: Locate and disarm traps

Vitality

Your Vitality score measures your ability to push on and endure harm. Damage reduces Vitality, and when it reaches zero, your character is overcome — dead or severely injured. Damage to your Vitality is measured in Wounds. If you are told to Take a Wound, you reduce your Vitality by one. (Sometimes you may be told to Take two Wounds, or more).

You may sometimes be told that damage ignores armour (e.g. from drowning or hunger), in which case the loss cannot be prevented by armour (see below). You may also be told to Heal one Vitality, which allows you to heal a point of lost Vitality.

Most adventures will tell you what to do if you reach zero Vitality. If they do not, your character dies and the adventure is over.

Some adventures offer opportunities to Rest, which generally involves consuming a ration (see Equipment, below). When you rest you will usually be told to restore some Talent and heal some Vitality. Sometimes, if you don’t have a ration, you will lose Talent or Vitality instead.

Magic

Spells are magical rituals that must be inscribed on scrolls, tablets, or other items, because unleashing the spell destroys the item that contains it. Although a spell can be memorised and cast without an item, this damages the wizard's brain, and player characters never do this.

If you have a spell, you may cast it when instructed to do so in the text (e.g. Cast Fly) by Testing against a 10. If you succeed, the spell is cast and then destroyed. If you fail, you choose either:

  • The spell is destroyed without effect
  • You Take one Wound, ignoring armour and keep the spell

If you keep the spell, you can try to cast it again at another time.

Standard Spells

The following spells have standard uses:

Dispel
Ends a magical effect on you, or something you touch (use when indicated)
Fireball
When fighting a group of enemies, automatically win a round
Flight
Allows you to briefly take flight (for about a minute) and then land again (use when indicated)
Invulnerability
Cast after a failed Fight test to ignore any Wounds
Swim
Allows you to breath and move underwater for a short period (about ten minutes) (use when indicated)
Teleport
Transports you instantly a short distance, possibly escaping a situation (use when indicated)
View
Allows you to view an adjacent area or peer inside a sealed container (use when indicated)

Example

You teeter on the edge, fighting for balance, but the entire ledge collapses beneath you. If you have a flight spell and cast it, turn to 4, otherwise turn to 124.

In this example you can escape the fall if you have a flight spell in your inventory (or an item that casts one). You must also successfully cast it by rolling a 10 or less on 2d6. If you cast the spell successfully it is destroyed, but you choose option 4. If you fail to cast it, or do not have it (or choose not to use it) you choose option 124.

Spells in GNAT are a consumable resource, treated much like items, but with predictable effects that encourage players to carry them from one adventure to another.

Combat

Combat is a special case of testing Talent. When you face combat, you will be told to Fight. To Fight, Test your Talent. If you pass, you win the fight. If you fail, you Take a Wound.

Many combats involve a penalty, to represent the strength of the opponent, and some last multiple rounds — which means you must test your Talent multiple times. For example if you are told to Fight three rounds at -3, that means you must test your Talent three times, with a -3 penalty on each roll, taking one wound for each round you fail. If you are still alive at the end of the three rounds, you win the fight.

If you Fumble in combat, increase the damage you take (if any) for that round by one Wound.

Examples

Stepping into the chamber, you find yourself assaulted instantly by a guard who was hiding behind the door. Fight one round at -2. Because you are surprised, you cannot use a shield. If you survive turn to 4, otherwise turn to 124.

In this example you must Test your Talent with a -2 modifier. If you fail the test you Take 1 Wound. Normally you could use a shield (if you had one) to reduce the modifier to -1, but in this case you cannot use the shield. If you are reduced to 0 Vitality you choose option 4, otherwise you survive, and choose 124.

You face up to the mob of goblins, who attack you at once. Fight three rounds at -3.

In this example you must Test your Talent with a -3 modifier, three times. For each test you fail you Take 1 Wound. If you have a shield you can reduce the modifier to -1 because there are multiple enemies.

Combats in GNAT are a matter of survival. You win a combat by not being dead by the end. The default combats last only one round and do one wound, so if you enter the combat with more than one wound you cannot lose (barring a fumble).

Gamebook authors are not obliged to list the standard modifiers (e.g. a shield providing -2 instead of -1) unless they do not apply for some reason, but may always choose to do so.

Weapons, Shields, and Armour

Your character can carry multiple weapons, a shield, and a suit of armour, each of which give bonuses in combat. If you are carrying more than one weapon, you choose which to use at the start of combat. If you have no weapon, fight at -1.

One-Handed Weapons (such as swords, axes, daggers, maces) require one hand to use (allowing you to also use a shield), and may give a bonus to your Talent in combat. e.g. you may find a Sword (+1).

Two-Handed Weapons (such as greatswords, or heavy maces) require both hands to use (so you cannot use a shield). In addition to any bonuses, a two-handed weapon allows you to re-roll the first 6 you roll each round when fighting — you must take the second result.

Long Weapons (such as spears or polearms) require both hands to use (so you cannot use a shield), but do not have the two-handed bonus. However, they may sometimes provide an extra bonus where their length is relevant.

Ranged Weapons (such as bows) require both hands to use (so you cannot use a shield), and do not give a bonus in combat. However, you may find certain actions only open if you have a ranged weapon.

Shields require one hand to use (so you cannot use a shield and a two-handed weapon). Shields reduce any combat penalty you suffer by 1, or by 2 if you face multiple opponents at once.

Magical Weapons can be one or two-handed, ranged or long. In addition to their normal bonuses, they also give you Advantage (see below).

Armour comes in Light (1 protection), Medium (2 protection), and Heavy (3 protection) varieties. When you take a wound while wearing armour, you may choose to ignore the wound — and you may do this a number of times per adventure equal to the protection value. Some adventures may offer the chance to repair your armour, which restores its protection value.

When wearing armour, you take a penalty to Stealth, Swimming, and Climbing skills equal to the undamaged protection value.

Advantage and Disadvantage

Sometimes you will be fighting with a distinct advantage — such as when you are flying and your target is not. When you have Advantage you may re-roll any one dice — you must take the second result. You make this re-roll after any other re-rolls (e.g. from a two-handed weapon).

Sometimes the opposite is true, such as when your target is flying and you are on the ground. In this case you have Disadvantage and must re-roll the first 1 or 2 you roll each round when fighting — taking the second result.

An adventure will specify when Advantage or Disadvantage applies.

Equipment

During your adventures you may pick up many pieces of equipment, such as a jewelled dagger, a ration, a flight spell, or a pickled serpent’s head. These will be marked in bold. You also have a Coin Pouch that holds any number of gold pieces (gp), which can be spent to buy other items.

You can carry as many of these normal items as you wish, but the same is not true of Heavy Items. The total number of heavy items you can carry is equal to twice your maximum Vitality.

Weapons, shields, and armour are all heavy items. If some other item is heavy it will be listed in the adventure where you find it, e.g. barrel of ale (heavy).

You will sometimes find items marked as treasure, e.g. gold ring (treasure, 40gp). You cannot spend these items directly, but can sell them for the indicated price at locations where you are told that someone will buy treasure.

Some items give a bonus to a Skill (e.g. "Tome (+1 occult)"). In this case you count this bonus to your Talent whenever testing that skill. If you carry multiple items that give a bonus to the same skill, only the highest applies.

Many systems limit the number of items a player can carry to force choices. However, in a system where characters may travel from adventure to adventure, players may wish to keep items across games. By limiting only heavy items, choices can still be presented while items not relevant to the current adventure can be retained.

Standard Equipment Prices

  • One-handed, or ranged weapon — 20gp
  • Two-handed, or long weapon — 25gp
  • Shield — 20gp
  • Light Armour — 40gp
  • Medium Armour — 100gp
  • Heavy Armour — 250gp
  • Rations (each) — 5gp
  • View Spell — 100gp
  • Flight Spell — 150gp
  • Invulnerability Spell — 50gp
  • Rope (+1 climbing, heavy) — 50gp
  • Bestiary (+1 naturalist, heavy) — 200gp
  • Tome (+1 occult, heavy) — 200gp
  • Healing Potion (Heal 3 Vitality) — 100gp

Keywords and Titles

During your adventures you may gain vital clues, or participate in certain events, which are marked by Keywords, which are given in italics, e.g. “Gain the keyword Arbalest”. Keywords are not equipment, and aren’t lost if you lose your items.

You may also be awarded Titles, which are measures of respect and rank. Titles may give you access to certain restricted parts of adventures. Like keywords, titles are not equipment, but they can be removed by adventures. Some adventures record Status, which is a sort of title that has a numerical score: e.g. “Status 2 with Treysham”.

You do not need to retain keywords after completing an adventure, but you may find a title awarded in one adventure referred to in another.

Keywords are used to track progress within a given adventure. After an adventure is over, the player does not need to retain them. Titles provide a way to transfer progress from game to game.

After the Adventure

At the end of an adventure, the author may supply instructions on what to do with particular items (such as discarding ones that have no use ourside that adventure), and offer a price list for selling items acquired during the adventure.

After an adventure is completed, do the following:

  • Reset your Vitality and Talent to their maximum values.
  • Optionally, discard any items from your inventory.
  • Optionally, sell any Treasure items for their value.
  • Optionally, buy any items you wish from the standard equipment list.
  • Optionally, spend Experience, as described below.

Experience

If you are successful in your adventures, you will be awarded one or more Experience Points (xp). You can spend these points to increase your abilities in one of the following ways:

Increase Talent: pay experience points equal to your current Talent to raise it by one level. For example, to increase from Talent 6 to Talent 7, pay 6xp.

Increase Vitality: pay experience points equal to twice your current Vitality to raise it by one level. For example, to increase from Vitality 3 to Vitality 4, pay 6xp

Advance a Skill: pay experience points equal to your current bonus in a Skill to raise it by one level. For example, to increase from Climbing +2 to Climbing +3, pay 2xp.

Gain a Skill: pay 2 experience points to buy a new Basic Skill.

You may spend experience between adventures, or any time you take a Rest during an adventure. If you spend Experience during an adventure to raise a stat which is not at its maximum value, only the maximum value increases.

Experience points may be awarded during the course of an adventure, for completing specific goals, or at the end of an adventure, depending on author preference. An adventure may also award direct increases in Talent, Vitality, or Skills instead of, or in addition to, xp awards.

Creating a new character

To create a new character:

  • Set your Talent to 9
  • Set your Vitality to 3
  • Gain two Basic Skills
  • Pick a One-handed, Long or Two-handed Weapon
  • If you took a One-handed Weapon you may take a Shield
  • Gain 1 ration and 10 gold pieces

Optionally, you may reduce your Talent by one to gain another Basic Skill. You may do this up to three times.