The Rules of Invention
This document provides an outline of the rules and procedures for inventions found in GURPS Basic Set. It is no substitute for reading those rules. Inventors and gadgeteers should be intimately familiar with the rules in detail, and should refer to this sheet only as a quick guide.
Definitions
Invention: “realistic innovation at the inventor’s tech level – or one TL in advance of that, at most” (Basic 473).
Gadgeteer: “larger-than-life inventor who can build more fantastic gadgets” (Basic 473).
Gadgeteering Advantage: “lets you design gadgets quickly, and makes it easy to realize higher-TL innovations (Basic 57).
Weird Science: “crackpot scientific theories that are far ahead of their time” (Basic 228).
Required Skills
Required: Design skill from the Engineering Triad (B190) or similar appropriate skill.
Bonus: Weird Science skill allows +5 to any "sufficiently weird" invention.
Complexity
The GM assigns Complexity.
| Complexity | Required Skill Level | Retail Price |
|---|---|---|
| Simple | 14 or less | Up to $100 |
| Average | 15-17 | Up to $10,000 |
| Complex | 18-20 | Up to $1,000,000 |
| Amazing | 21 or more | Over $1,000,000 |
Concept Roll
GM rolls vs. Character Skill to determine if theory is testable.
Modifiers:
- -6 if the invention is Simple, -10 if Average, -14 if Complex, or -22 if Amazing.
- Gadgeteer: -0 if the invention is Simple, -2 if Average, -4 if Complex, or -8 if Amazing.
- +5 if you have a working model you’re trying to copy
- +2 if the device already exists but you don’t have a model
- +1 to +5 if the item is a variant on a existing one
- -5 if the basic technology is totally new to the campaign (regardless of TL)
- -5 if the device is one TL above the inventor’s TL
- Weird Science: +5 if the invention is sufficiently weird
On success, inventor has successful theory and may proceed to Prototype.
On failure, inventor knows his theory is bad and may roll again next day.
On critical failure, the inventor thinks he has a workable theory and proceeds to Prototype.
Prototype
Roll vs. inventor’s skill. Use same modifiers as Concept roll, plus:
- +1 per assistant with skill 15+ (max: +4)
Each Prototype roll requires 1d-2 days if the invention is Simple, 2d days if Average, 1d months if Complex, or 3d months if Amazing.
Side effects may be adjusted or eliminated by modifying the device. This is done by returning to the Prototype stage and rolling against an appropriate Repair or Design skill. A successful modification results in the elimination of the side effect, but a new random side effect occurs. Only a critical success on the modification (Prototype) roll results in the elimination of all side effects or bugs.
Critical success on the Prototype roll means there are no random side effects.
Cost
No bucks, no Buck Rogers. The prohibitive costs of invention demand either a sufficiently wealthy Patron, or personal Wealth 2 (Wealthy) or greater.
Other Rules
A character may attempt a Weird Science roll whenever working on a new invention or investigating an existing item of weird technology. Success results in a +5 on Concept and Prototype rolls, or +2 to any skill roll made in the analysis of an existing item.
Technology adapted or invented using Weird Science rules is subject to the rules governing Weird Technology (Basic 479), including random side effects.
Gadgeteer rules apply only to inventors with the Gadgeteer advantage (Basic 475).