Coverage Checklist and Gap Analysis
What a military science-fiction combat system must handle, derived from a survey of openly licensed and freely available systems. Functional coverage only — what situations need a rule and what a mechanic structurally does. No rules text, tables, or values from any surveyed system, per the originality policy.
Naming a source in design discussion is permitted. Discussion is not publication.
The headline finding
The open corpus is rich on personal combat and rich on spacecraft combat, and almost entirely empty in the middle.
That middle — squad morale, suppression as a tactical grammar, communications, logistics, CBRN, casualty evacuation, and electronic warfare against the command layer — is exactly what makes a game feel military rather than merely armed. It is unclaimed.
C.A.T.S. should be built there.
The gap list, ranked by opportunity
Situations where no open system serves, ordered by how badly the corpus fails and how valuable the space is. This is the design opportunity list.
| # | Gap | Note |
|---|---|---|
| 1 | CBRN and protective posture | Contamination persistence, detection and alarm, dressing time, degraded capability while suited, decontamination, tempo cost. Zero open coverage. Total greenfield |
| 2 | EW against the command layer | Every open system treats jamming as a to-hit modifier. Nobody makes it degrade activation, orders, and coordination. Highest-leverage unclaimed idea found |
| 3 | Drones, remote weapons, operator-link severance | Defines contemporary war. Modelled nowhere |
| 4 | Logistics as a campaign layer | Wargames assume ammunition away because scenarios are short. That assumption breaks in an RPG |
| 5 | Medical as a tactical cost | Nobody models the consequence of having wounded — CASEVAC consuming a fireteam's combat power, triage under fire |
| 6 | Squad-scale morale | Nothing sits between individual fear and army-scale mass battle. "Does this fireteam break?" is unanswered |
| 7 | Indirect-fire sophistication | Counter-battery, time on target, pre-registered fires, danger close — all absent |
| 8 | Multi-spectral signature | Separate visual / thermal / radar / emissions profiles defeated by different sensors. C.A.T.S. is already building this from physics — see the space and to-hit models |
| 9 | Newtonian space movement and vacuum stealth | Barely attempted, and emissions-based detection is untouched. Also already ours |
| 10 | CQB, room clearing, breaching as a discipline | The entire close-quarters domain is a hole |
| 11 | Fortification assault, trench fighting, bunker reduction | Absent as subsystems |
| 12 | Hasty vs deliberate ambush; counter-ambush; counter-sniper | Absent as procedures |
| 13 | Fire and movement / bounding overwatch as a named, rewarded action | Emerges structurally in one wargame; never explicit |
| 14 | Communication failure, delayed or garbled orders, delegation | Abstracted as activation friction, never modelled as comms |
| 15 | Boarding and hull breaching, especially at capital scale | Nearly untouched |
| 16 | Ground-vehicle crew stations | Open systems assign crew roles for starships but never for tanks |
| 17 | Reactive armour, spall, top-attack, ammunition cook-off | Thin to absent |
| 18 | Injury that is both mechanical and narratively invokable | Everyone does one or the other, never both |
| 19 | Non-lethal capture as a real tactical trade | Nobody mechanises the decision |
| 20 | Unit-scale mass combat, mercenary contracts as working subsystems | Absent |
Three of these — multi-spectral signature, vacuum stealth, and Newtonian movement — C.A.T.S. already covers by having started from physics rather than from genre. That is not a coincidence: they are gaps precisely because they need real physics to model honestly.
Suppression is the most important military mechanic
The survey is unambiguous about this, and it bears directly on OQ-26, which flagged that C.A.T.S. currently has no volume-of-fire representation at all.
Three distinct structural solutions exist:
| Approach | How it works |
|---|---|
| Zone control | Firing consumes ammunition to establish a threatened area, converting firepower into area denial rather than damage |
| A status condition | Suppression is a state penalising attack and movement, applied by weapons with an appropriate trait |
| The primary output of shooting | The main effect of fire is suppression; casualties are the side effect |
The third inverts the usual assumption and is the most military-feeling of the three.
The pattern worth adopting is two-axis: a short-term suppression flag plus a persistent confidence tier that steps down through willingness states — advance, hold, withdraw, break — as a unit takes casualties or loses its leader. Better training absorbs more suppression before breaking, which is what makes asymmetric fights work without fudging lethality. Rally is then a leader action tested against troop quality, so both quality and leadership pay off in recovery.
This also answers gap 6 (squad morale) with the same mechanism.
Structural ideas worth deriving
| Idea | Why it matters for C.A.T.S. |
|---|---|
| One progress-track primitive, reskinned everywhere | Chases, influence, research, infiltration, hacking, repair and hexploration all run on one accumulator. This validates our Margin-and-progress model — we already have the primitive; the lesson is to reuse it aggressively rather than inventing subsystems |
| Sense taxonomy: precise / imprecise / vague | Layered over an observed / hidden / undetected state ladder. Makes "thermal imaging is imprecise" expressible without new rules — directly useful for our sensor model |
| Detection as a distinct step | Whether you see a unit depends on range, whether it moved, whether it fired, and its cover. Staying still is a mechanic, not flavour |
| Cover and concealment kept separate | Cover is protection; concealment is not being seen. Most systems collapse them, which is wrong for a military game — they are different resources with different failure modes |
| Phased combat by crew station | Combat resolves in named phases and each crew member acts in theirs. The cleanest solution to "only the pilot has anything to do" |
| Minor / major / push action tiers | Guarantees an understaffed or unskilled seat still contributes without a check |
| Mobility kill / firepower kill / catastrophic kill | Three distinct vehicle outcomes rather than one hit-point bar. Maps onto our depth-tier model |
| Scan as an information ladder | A better check reveals progressively more — specs, then defences, then weapons. Information as a combat resource |
| Two-directional time modifier | Pricing rushing and preparing symmetrically. Cheap and expressive |
| Success at a cost priced into the dice | Re-rolling a failure costs attribute damage, gear degradation or stress, rather than being GM-adjudicated |
| Degree of success as a menu of effects | One roll produces both magnitude and the character of the outcome. Our Margin already does the first half |
| The technological / analog tag pair | Tagging gear as one or the other, with a glitch condition on the former, makes EMP, hacking and ion weapons real without bespoke rules |
| Half-health as an inert trigger hook | A threshold that carries no penalty itself but that other rules can key off |
Situations C.A.T.S. must not forget
Compressed from the full survey. Anything unchecked here is a hole in the system.
Engagement: initiative structure · action economy · multiple attacks · delay and hold · overwatch and reaction fire · surprise and ambush · detection before engagement.
Position: cover by degree · concealment separately · flanking · elevation · prone and stance · engagement and disengagement · reach · gang-up · forced movement · hull-down.
Ranged: range bands · point-blank and extreme · aiming as spent time · fire modes and autofire · suppression · firing into melee · firing while moving · area and sweep · called shots · reload and ready · jams and malfunctions · optics.
Close: active defences · shields · defensive stance · grappling · disarm, trip, shove · knockback · stun and subdue · breaking objects · helpless targets.
Environment: light levels · night-vision tradeoffs · smoke, including multi-spectral · camouflage · weather · vacuum and decompression · atmosphere types · radiation · zero-g · fire, falling, drowning, poison, disease, deprivation.
Explosives: area templates · grenades and scatter · indirect fire with call-to-impact delay · minefields · demolitions · anti-armour penetration vs protection by facing.
Psychology: morale and rout · suppression recovery and rally · fear and panic · stress as a parallel track · long-term attrition · unit cohesion and veterancy.
Scene and campaign: chases · boarding · mass combat · faction layer · contracts · sieges · orbital assault.
Electronic: electronic defence as its own attack surface · hacking as a combat action · lock-on and target designation · ECM and jamming · drones.
Sustainment: ammunition · encumbrance · resupply · maintenance · fatigue over days · wound states and first aid · bleed-out clocks · CASEVAC.
Licensing conclusion
The survey reached the same conclusion the originality policy already sets, with more force behind it.
Take no license. Write it all ourselves.
- Mechanics are not copyrightable. US statute excludes any procedure, process, system, or method of operation. Reading a game grants the right to use its ideas.
- Expression is protected, and that is where trouble actually happens: rules prose, examples of play, flavour text, transcribed tables, art, layout, and trade dress.
- On tables specifically: numbers you derived are safe; numbers you transcribed carry the compiler's thin copyright in their selection and arrangement. C.A.T.S. derives all of its own ballistics and armour maths anyway.
- Trademark is where the money risk lives — names, logos, and compatibility badges, with no idea/expression escape hatch. Worth a trademark search on the title; not worth a license review.
- Do not claim compatibility with anything without that publisher's compatibility license.
- Reciprocal licenses would force every mechanic in a single-system book into the commons, including the combat engine that is the whole point.
Practices already in AGENTS.md and the originality policy — write from understanding with the source closed, derive our own numbers, name everything ourselves, keep dated design notes — are exactly the right ones. Independent creation is a complete defence, but only if it can be shown.
Verification flags
The survey could not settle several licensing details and flagged them explicitly. None affect C.A.T.S. while we incorporate nothing, but they matter if that ever changes: several publisher SRD licensing pages are dead or unreachable, at least one product carries open-license boilerplate while declaring none of its content open, and one widely cited system's books and SRD sit under different licenses. Read the actual declaration in the actual document, every time.