Ed of Two Hour Wargames wrote that the Chain Reaction rule-set actually is like a toolbox. I must say, I enjoy the system very much and the variants I introduced in my solo games mostly are just simplifications.
- During each turn, I just activate all the figures of both sides. I only roll two dice at the very start, to see who goes first. I then alternate. The Reaction system guarantees that things don’t get boring and rigid.
- I don’t use the “fast movement” option. My playing space is so small, that I don’t want figures to move too much in a single activation.
- I don’t use the “Outgunned” ruled. Most of my figures are armed with rifles, and those with pistols are stars. Even when I tried more variety, I really don’t mind rolling several exchanges of fire / received fire.
- When the rules require to roll REP dice, I roll D6+REP instead. These are opposed rolls, to see who scores the highest result. Since I roll both sides at the same time (with different colored dice) to me it’s much more convenient to roll tow dice than (say) eight or ten.
- I only place three PEFs on the board (which, I repeat, is very small). I don’t used additional PEFs for buildings. I use my custom PEF resolution tables that are tuned to generate an opposition whose average equals my squad but that is highly variable (I can easily get half, or double, the strength of my squad).
After this first pass of simplification (during the Zurqana campaign) I started a second campaign (Ybeena) with two new types of figures: Aliens and Robots. For this, I heavily stole from Illegal Aliens, a supplement that Ed graciously made freely available.
This PDF provides the details. The first page lists the different types of figures and my custom Potential Enemy Force (PEF) resolution table; the second page provides details for Robots and Aliens. It’s something I have made as a playing-aid for myself: nothing fancy.
The Robots are simple. Being machines, they don’t roll Received Fire or Man Down reactions. The model that can shoot (rockets) only does so once per turn: to reduce book-keeping, I decided it can only shoot during its activation (not as a result of an In Sight test during enemy activation).
They have a custom Damage table (from Illegal Aliens, “Robotic Troopers”) with the fun feature of the Robot occasionally exploding (causing damage similar to a grenade to nearby figures).
Coming up with something playable for the Aliens has been harder. At the end, they turned out to be quite low tech. In my imagination, this is due to their deliberate decision to go hunting for humans without the full power of their superior technology. They mostly fight with “blades” in melee. Once per turn (when they are active, as for the Robots) they can fire their “built-in” eye-ray, which is not very effective anyway (a single Target die).
They have their own reaction tables, basically making them more cold-blooded than humans. Additionally, they must take a test when an enemy or another alien goes down: if they fail the test, they will start feasting on the body and will be distracted for a variable number of turns (this is also derived from “Illegal Aliens”: Lycaon).