Creating a Custom Sci-Fi BRP TTRPG

Creating a custom science fiction tabletop RPG from Basic RolePlaying (BRP) Game Universal Game Engine

Understanding the Basic Roleplaying (BRP) System

The Basic Roleplaying (BRP) Universal Game Engine, published by Chaosium, is a flexible d100-based system designed for adaptation across genres. It’s the core engine behind games like Call of Cthulhu (horror), RuneQuest (fantasy), and others. Its strength lies in modular rules for character creation, skills, combat, and optional mechanics like powers or vehicles, making it ideal for building a custom science fiction (sci-fi) tabletop RPG. The system emphasizes percentile rolls for resolution, where success depends on skill levels and situational modifiers. Since BRP is released under the Open RPG Creative (ORC) License, you can create and distribute custom games royalty-free, as long as you credit Chaosium and follow the license terms. This includes sci-fi adaptations, where you might incorporate elements like mutations, psychic powers, superpowers, advanced weapons, and spacecraft.

To start, obtain the Basic Roleplaying: Universal Game Engine core book (available digitally or in print from Chaosium’s site or retailers like DriveThruRPG). It includes all foundational rules. You can also download the free BRP ORC Content Document (in RTF or PDF format) from Chaosium, which serves as a System Reference Document (SRD) for building your game.

Steps to Create Your Custom Sci-Fi RPG

Here’s a step-by-step guide to adapting BRP for a sci-fi setting. This draws from official design guidelines and community experiences, focusing on customization while keeping the game balanced and playable.

1. Define Your Setting and Core Concept
   Begin by outlining the sci-fi world: Is it space opera (e.g., interstellar empires, alien alliances), cyberpunk (high-tech dystopias), hard sci-fi (realistic physics and exploration), or post-apocalyptic (ruined worlds with salvaged tech)? Decide on themes like exploration, combat, intrigue, or survival.

• Think about player roles: Pilots, hackers, bio-engineers, or alien diplomats?
• Identify key elements: Faster-than-light travel, AI companions, energy weapons, or genetic modifications.
  This step ensures the rules support the narrative. For example, if your game involves space battles, emphasize vehicle rules; for psychic phenomena, adapt the psychic powers module. Aim for a focused scope—start small to avoid overwhelming complexity.

1. Master the Core Mechanics and Select Options
   BRP’s base system uses seven characteristics (Strength, Constitution, Size, Intelligence, Power, Dexterity, Appearance) rolled on 3d6 or similar, plus skills rated 1-100% (e.g., Pilot 50%). Actions resolve with a d100 roll under the relevant skill, modified by difficulty. Combat is deadly and tactical, with hit locations and damage types.
   Customize by choosing optional rules from the core book to fit sci-fi:

• Character Creation: Add sci-fi backgrounds (e.g., cybernetic implants boosting stats) or professions (e.g., Spacer, Scientist). Replace fantasy skills like “Ride” with “Drive Spacecraft” or “Hack Computer.”
• Powers and Abilities: Use mutations for alien races, psychic powers for telepaths, or superpowers for enhanced humans. For tech-heavy games, reskin magic as nanotechnology or AI hacks.
• Combat and Equipment: Incorporate energy weapons (lasers with armor-piercing), armor (force fields), and vehicles (starships with hull points and maneuver ratings). Add rules for zero-gravity fights or hacking drones.
• Other Modules: Include Sanity for cosmic horror elements (e.g., encountering eldritch aliens), or Fatigue for resource management in harsh environments like space stations.
  Scale power levels: Normal humans for gritty sci-fi, or epic tiers for heroes battling interstellar threats. Optional Rule Core BRP Use Sci-Fi Adaptation Example Hit Locations Tracks damage to body parts for realism Energy shields protect specific areas; cyber-limbs have separate hit points Psychic Powers Mental abilities like telekinesis Reskin as psionic implants or alien mind powers; add hacking as a “psychic” skill for digital realms Mutations Random physical changes Genetic engineering or radiation effects; e.g., extra limbs for multi-tasking in zero-G Vehicles Rules for chases and combat Expand to spaceships with FTL drives, weapon turrets, and sensor scans Sanity Mental stability loss Void madness from warp travel or AI corruption

1. Build Custom Content

• Characters and Races: Create templates for humans, aliens, androids, or uplifted animals. Assign characteristic bonuses (e.g., aliens with high Dexterity for agility in low-gravity).
• Worldbuilding: Detail planets, factions, and tech levels. Use BRP’s equipment lists as a base—add items like plasma rifles, exosuits, or neural interfaces. For economies, adapt wealth rules to credits or resource scavenging.
• Adventures and Campaigns: Design scenarios around sci-fi tropes (e.g., colony outbreaks, corporate espionage). Provide GM tools like random encounter tables for asteroid fields or alien artifacts.
  If basing on existing BRP games, import elements: e.g., borrow horror mechanics from Call of Cthulhu for a “space eldritch” vibe, or fantasy creatures from RuneQuest reskinned as bio-engineered monsters. Community examples include homebrew sci-fi campaigns with added rules for faster-than-light travel or AI companions.

1. Balance, Playtest, and Refine
   Run test sessions with friends to check mechanics. Ensure sci-fi elements don’t unbalance core BRP lethality—e.g., high-tech armor shouldn’t make combat trivial. Adjust difficulties (e.g., hard sci-fi might penalize rolls in vacuum). Gather feedback on fun factor: Does hacking feel engaging? Are space chases exciting?
   Iterate: Simplify overcomplicated rules, as BRP shines in streamlined play. Tools like spreadsheets can help model probabilities for d100 rolls.
2. Publish or Share Your Game
   Format your rules into a PDF or booklet. Use the ORC License notice in your document. Distribute via platforms like DriveThruRPG, itch.io, or forums like Reddit’s r/rpg. For inspiration, check existing sci-fi BRP products on DriveThruRPG, such as apocalyptic settings with custom conditions.

Tips for Success

• Keep It Compatible: Stick close to core BRP for easy integration with other games—players familiar with Call of Cthulhu can jump in quickly.
• Genre Blending: Sci-fi pairs well with BRP’s optional horror or mythic elements (e.g., ancient alien ruins with Sanity-draining secrets).
• Community Resources: Join forums like basicroleplaying.org or Reddit’s r/rpg for advice on homebrew sci-fi. Watch design videos from Chaosium’s Jason Durall for deep dives on applying BRP to original settings.
• Avoid Overkill: Only add rules that enhance your sci-fi theme—BRP’s modularity means you can start simple and expand.