# Chain Reaction *Created:* 2023-12-09, *Modified:* 2026-10-05 ![[Chain Reaction 2026 (cover).jpg|600]] Two Hour Wargames sells its whole identity on a single bet: teach you one set of mechanics, and the rest of the catalogue sells itself. **Chain Reaction** is that bet, handed out for free — a man-to-man combat engine you're supposed to learn once and then recognize running under every **[[Two-Hour Wargames|Two Hour Wargames]]** product that cares to admit it. It covers firearms and melee, plays in any period with any figures you already own, and can be fought solo, co-op, or head-to-head. The pitch is disarmingly simple, and it mostly works. ## Setting Chain Reaction doesn't come with a world, and it's not pretending to. It's a universal combat kit that refuses to care what you drop into it. The intro bills it as playable for "WW2, Zombies, Pulps, and more," and the back half makes good on the threat: quick **Lists** generate whole Bands by type — the default modern set (Movers, Joes, Exotics, Criminals) covers gang warfare and civilian life, then the book drifts into a post-apocalyptic zombie siege, a **Sword & Sorcery** appendix (Dwarves, Elves, Goblins, Men, Orcs, and Skeletal Undead), and a **Sword & Shield** nod for Vikings. You're a **Star** — the one character on your side with any agency, Rep 5 by fiat — leading a **Band** of whoever the Lists hand you, pointed at a **Mission** (military: Attack, Defend, Patrol) or a civilian **Encounter** (Chillin', Gamble, Confrontation, Escort, Robbery). There's no grand setting to learn because the whole point is that you're meant to bring the setting with you. ## Mechanics The signature is the **THW Reaction System**, and it's why the game feels different from a bog-standard I-go-you-go wargame. When you move part of your force, your opponent gets to react *immediately*, during your turn, and that reaction can pull a reaction out of you in turn. Everything hangs on the **Action Test**: each Band's Leader rolls **2d6 versus Reputation (Rep)**, every die equal to or under the Rep is a pass, and the higher sum of passed dice goes Active first (a tie means both sides fire simultaneously). Rep is the load-bearing stat — a fusion of experience, morale, and motivation — with three dial settings: 5 (confident Stars), 4 (veterans), 3 (the green and unwilling). ### Character Creation Character and figure are interchangeable, and a figure is defined by the answers to a short list of questions: - **Star or Grunt** — Stars are the players' characters (Rep 5) and get two advantages over the mechanical cast: **Star Power** (a pool of d6 equal to Rep used to shrug off disabling damage) and **Free Will** (always passes 2d6 on the Stay or Go Table and can pull the whole Band out of a fight). - **Class** — Movers, Joes, Exotics, or Criminals, the four buckets for every profession across every period. A **Psy** (sci-fi/cyberpunk) or **Caster** (fantasy) sub-Class adds mental blasts and actual fireballs, one per side. - **Reputation** — rolled via the Class Lists, which hand out Rep, weapon, and attribute per Band position. - **Attribute** — an optional 2d6 roll that colors the figure's Rep in specific situations: Coward, Runt, Slow to React, Near Sighted, Rage, Crack Shot, Quick Reflexes, Hard as Nails (or a shrug and a "Nothing"). ### Combat Weapons fit three fire categories — **Single** (one target), **Burst** (two), **Auto** (three) — at ranges of 12", 24", or 48". Shooting uses the **Shooting Table**: roll 2d6 versus Rep, add all passed dice, and compare the total to the target's Rep. Beat it and the target goes **Out of the Fight**; match or miss and it reacts (returns fire, charges into melee, or loses its nerve). Second and third targets defend at +1 and +2 Rep, and cover adds another +1. The four damage states climb from **Shaken** (emotional, not physical) through **-1 to Rep** (a melee bruise that recovers once the melee ends), to **Out of the Fight** and **Leave the Fight** — with the **Stay or Go Table** deciding whether a battered figure holds ground, gives in to being Shaken, or simply runs for it, and **Recovery** determining who's fit to come back after the fight. ### Solo Play The solo bones are the honest heart of it — as the book puts it, designed for solo, "not can be played solo." The uncertainty comes from **PEFs (Possible Enemy Forces)**: the table's seeded with markers you don't know the contents of, placed in cover, and only resolved into an actual enemy Band (or nothing at all) the moment your Band comes into sight. You don't get to know what you're meeting, or how many, until it's already in front of you. ## Editions Chain Reaction has been Ed Teixeira's free gateway for decades, and the library walks most of the road with it. - **Chain Reaction 3.0** (2003). *In the library* (multiple copies). - **Chain Reaction 3.1** and **Chain Reaction 3.1 Final Version** and the **Swordplay** variants (2000s). *In the library*. - **Chain Reaction 2015** · **Chain Reaction 2018**. *In the library*. - **Chain Reaction 2023** (2023) — the freely-reissued intro, the version the garden's own editing hands touched. *In the library.* - **Chain Reaction 2026** (2025/2026) — the current edition, expanded into a fuller standalone with the zombie and sword & sorcery appendices and the solo PEF layer (the library holds the early 47-page draft and the expanded 68-page **v2**, current). *In the library.* ## Supplements *All in the library.* - **Points Costs** — star-points and equipment costs for CR 3.0 and most THW games. - **Mortars** — mortar rules for CR 3.0. - **Adds to Chain Reaction 3** — a short rules-addendum sheet for CR 3.0. - **Gangsters for CR 3.0** — free Prohibition-era figures-plus-scenario add-on. - **Cereal Killers for CR 3.0** — free figures-plus-scenario add-on. - **Dog Soldiers for CR 3.0** — free add-on built around the lycanthrope *Dog Soldiers* scenario. - **Day of the Scourge** — a CR 3.0 adventure (Rebel Minis). - **Santa Claus Wars** — a Christmas-themed CR 3.0 supplement (2009, based on the Wargames Supply Depot miniatures line). - **Chillin' 2023** — a CR civilian Encounter module (hanging out / downtime scene). - **Xmas Heist** (2024) — a THW holiday scenario. - **Exporting CR 3.1** — the 2d6 PEF (Possible Enemy Force) movement table for solo play. - **Old School Chain Reaction** — the one-page "old school" play/reference sheet for classic Chain Reaction. - **12-Inch Battle Board** — a small-game battle-board system. - **Unlimited Reputation** — lets Rep climb without a ceiling: cash in your Increasing Rep d6, a 6 on each buys a point (Star Power climbing with it), while a roll of 6 stays a failure on the tables and the enemies get tougher to match. - **Chain Reaction New Edition Notes** — the editor's line-edit and design-critique notes on the 2026 draft. The line's campaign-scale siblings — **[[Warrior Heroes|Warrior Heroes]]**, **[[5150 - New Beginnings]]**, **[[NUTS!]]**, **[[All Things Zombie]]**, **[[Red Ops 5]]**, **FNG**, **County Road Z**, **Battlespace** — all run on this engine. ## References - [Chain Reaction 2026 – free rules on the Two Hour Wargames site](https://www.twohourwargames.com/collections/free-rules/products/chain-reaction-2023) - [Chain Reaction 2026 on DriveThruRPG](https://www.drivethrurpg.com/en/product/463000/Chain-Reaction-2026) - [Two Hour Wargames – Free Rules](https://twohourwargames.com/collections/free-rules)