X-Com – One Roll Invasion Pool

I’m very impressed by the One Roll Engine (ORE) developed by Greg Stolze, especially as it has been utilized in Hollowpoint, a game in development by VSCA. I believe a variation of ORE may be just what X-Com needs to cut the GM workload by minimizing rolls.

ORE works like this: Players roll pools of dice, all d10s in original ORE, all d6s in Hollowpoint. The amount of dice rolled depends on characters’ skill at the associated action. The goal is to roll sets of numbers (pairs, three of a kind, etc) with larger sets usually meaning higher degrees of success, such as greater damage, higher initiative order, etc.

The best part of ORE is that one roll can give a lot of information, and for the purposes of X-Com, hopefully everything you need to know. Let’s take a closer look at using ORE for the Invasion Pool.

One Roll Invasion

In Leverage, whenever a player rolls a 1 a d6 complication shows up. In X-Com, when Commanders roll complications as they direct the organization, the d6 Complication will instead be a d6 added to the Invasion Pool. Throughout the game the Pool will grow and nothing (except maybe extreme measures such as destroying alien bases) can reduce the Invasion Pool.

Every Round, the GM will roll the Invasion Pool and the resulting sets will indicate quantity, quality, and objective of UFO activity during the next round. How? That’s the beauty of ORE.

Let’s assume there are 5 d6s in the Invasion Pool, and they roll the following results:

2, 2, 1, 6, 3

Each set indicates a UFO. The number of dice in the set indicates the type of UFO (1 die = Small Scout d4, 2 dice = Large Scout d6, etc) and the quality of its occupants. The numbers on the dice themselves indicate the mission the UFO is advancing.

The Mission assignments are built off of the GMs initial build-out of the invader’s overall goals, but a Mission list may look something like this:

  1. No Activity (Complication for the aliens)
  2. Harvest
  3. Infiltrate
  4. Terrorize
  5. Terraform
  6. Establish Bases

Thus, in the above example, there is one large scout UFO on a Harvest Mission, as well as 2 small scouts pursuing infiltration, and base establishment.

In another example, rolling 10 d6s in the Invasion Pool gives the following results:

2, 2, 4, 4, 4, 4, 5, 5, 6, 6

Thus, a Large Scout d6 is on a Harvest mission, a Small Battleship d10 is on a Terror Mission, a second Large Scout d6 is Terraforming, and a third Large Scout d6 is Establishing or Supplying Bases.

Rolling in Plain View

Rolling the Invasion Pool in full view of the players represents their knowledge from global reports of UFO sightings, but that doesn’t necessarily mean their own sensors can detect where the activity is taking place. Still players will be forced to allocate resources for the round to deal with the current threat or jeopardize their relationship with the nations they are supposed to be protecting.

Sets Over 5

I’m debating what to do with sets larger than 5. A set of 5 would produce a d12 UFO. The simplest way to go would be to consider dice in a set beyond 5 as an additional set. In that case, if I roll nine 2s in the example above, there would be one Huge d12 Battleship (for five of the dice in the set) and an additional d10 Battleship (using the four remaining dice in the set), both of which would be on Harvest missions.

That option somewhat cuts the value of the unlikely probability of such a large set. Another option would be to give the Huge harvesting Battleship (and it’s occupants) a bonus d10 feature or augmentation, like a Tractor Beam d10, Chronadium Alloy Armor d10, or Human Defectors d10.

Another option is breaking with standard CortexPlus mechanics and notating ship strength by a number of d6s, all of which are kept (added forthe final result). Then the set literally is the strength of the ship, and a 9d6 UFO will be much harder for X-Com craft to take down than a 2d6 UFO. I’m not sure what I think of this, since I’d rather keep to consistent notation methodology.

A variation on the previous option is for large UFOs to be Xd6 with no additional dice kept. This option would make larger ships just as easy to hit, but with much tougher hull to chew through before it will fall from the sky, meaning more time to send fire to X-Com craft.

What do you think?

Scaling Difficulty

I like the idea of games that can scale their difficulty. For instance, the board game Pandemic lets players choose how hard they want their virus-stopping quest to be. I can tell you from experience that failing one turn away from success on a superhuman game feels much better than succeeding on an easy game. The drama is in the tension right? The original X-Com games gave computer gamers that option, and a one roll Invasion Pool makes that same option available to RPG gamers.

Difficulty can be adjusted by varying the starting size of the Invasion Pool or by varying the number of “No Activity” results on the Mission List. For example, the pool could start with 0 or 2 dice for an Easy game, 5 for a Moderate game, 10 for a Hard game, and so forth. (I have no idea how these numbers would scale) Adjusting the Mission List could mean 1-3 all result in No Activity for an easier game. Starting with a large Invasion Pool but a sparse Mission List would make for sparse but dangerous enemies, while a smaller pool and larger list will make more frequent, less dangerous enemies.

Time-release Danger

An additional trick the Mission List allows is unlocking more dangerous missions as months and years go by. Maybe the Mission List starts with just sporadic Research Missions on results of 3-6. After a few months, the GM may adjust the Mission List (according to the aliens’ overall goals) and now a result of 2 introduces Terror missions, and then later, a result of 6 introduces establishing bases, and so on. Intelligent invaders will likely vary their approach and this gives GMs some leeway to adjust the game as fits the players and narrative.

One Roll Enemies

The ORE system would work wonderfully to create interesting and lethal alien species as well. The more dice you throw give a more dangerous foe. A very basic d6 species would be involve rolling 6d6, while a scary d12 species would roll 12d6. I’ll give examples of this application in a later post, but so far I’m really liking ORE.

What do you think? Can you see ORE fitting into the CortexPlus framework of X-Com?

About Adam

Adam is a husband, an explorer of the inexhaustible, and a hunter for unexpected synergies and collaborative potentials. His explorations into RPGs began with DMing D&D, though lately he enjoys mining the potentials of diverse systems, especially Cortex Plus.
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