RingBRP/docs/GM_SCREEN.md

THE CUSTODIANS — GM screen

Every number on this page was checked against rules.mjs on 9 September 2026 — 58 of 58 figures, by running the functions — not read out of the design specs. Where this and design/ disagree, the code is right and this page is stale — rules.mjs is the single authority, imported by both the runtime and the pack builder so that packs cannot be built under one rule and played under another.

How to read this

This is the sheet to have open while running, not the rules text. It carries the figures you reach for mid-scene and nothing you can look up afterwards.

Where these numbers live

what	file
every pure rule formula, and rolling, banding and grading	rules.mjs
the six specs in design/	review history addressed to Codex — not current rules

Rolling

The order of operations

Difficulty multiplies the rating first, then situational modifiers add.

difficulty	rating becomes
Easy	× 2
Average	unchanged
Difficult	÷ 2, rounded down

Then add circumstance and any other modifier. The result is clamped to 1–100, so nothing is ever truly impossible or certain. A skill with a printed base of 5 or more never drops below 5.

The circumstance ladder

Applied after difficulty. Capped at ±40 in total, however many apply.

Overwhelming	+30
Favourable	+20
Slightly good	+10
Neutral	0
Slightly bad	−10
Unfavourable	−20
Severe	−30

Reading the roll

From the effective chance, call it B:

band	is
Critical	ceil(B / 20) or less
Special	ceil(B / 5) or less
Success	B or less
Fumble	101 − ceil((101 − B) / 20) or more

Fumble is tested first. 96–99 never succeed, whatever the chance. 00 always fumbles.

Against armour: a critical ignores armour entirely; a special counts it as half, rounded down.

Reaction — who goes first

Reaction runs on two axes and takes the better of them:

• Reflex = ceil(DEX / 3)
• Awareness = ceil(Readiness / 10)

Base = 3 × max(Reflex, Awareness), then a d6 and a modifier capped at ±3. Marksmanship style is the agent's own choice — home worlds are gone, and nothing determines it for them.

The combat round

Defending

Every defence after the first in a round is cumulative −30%. Two defences is −60%, three is −90%. Standing in front of three people is possible and stupid.

Fire modes

mode	to hit	gives you
Slow	+10	reloads
Single	0	—
Fast	0	a second shot
Rapid	0	bursts
Beam	+5	sustain

A weapon with no mode set behaves as Single.

The second shot

−20% to both shots, not just the second. The cost of hurrying is that you hurried the first one too — which is what stops this being a free extra attack for anyone holding a revolver.

Bursts

burst	rounds	to hit
Short	3	−10
Long	6	−20
Full	10	−30

Hits are capped, not proportional:

	success	special	critical
Short	1	2	3
Long	2	4	5
Full	3	5	7

However many rounds connect, a burst is one wound event — one Major Wound check, not one per round. Every round in the burst leaves the weapon regardless of what hits. A failure or fumble connects with nothing.

Range

band	to hit
Short	0
Medium	−10
Long	−30
Extreme (to twice long)	−50
Beyond	cannot be attempted

Two weapons

−20% main hand and −40% off hand; if trained, −20% to both.

Damage and wounds

Hit points

HP = ceil((CON + SIZ) / 2) — standard BRP. Major Wound = ceil(HP / 2): a single blow of half your hit points or more.

The damage modifier

From STR + SIZ:

STR + SIZ	modifier
up to 8	−1d6
9–16	−1d3
17–24	0
25–32	+1d3
33–40	+1d6
41–50	+2d6
51–60	+3d6
61–70	+4d6
71+	+4 + ceil((total − 70) / 10)d6

Hit locations (1D20)

melee	ranged	location	share of HP
1–4	1–3	Right leg	42%
5–8	4–6	Left leg	42%
9–11	7–10	Abdomen	42%
12	11–15	Chest	50%
13–15	16–17	Right arm	35%
16–18	18–19	Left arm	35%
19–20	20	Head	40%

Ranged fire favours the chest, melee the legs — the two columns are different distributions, not one table read twice.

A location's own pool is that share of total HP, rounded up. At its maximum the location is disabled; at twice its maximum, destroyed. Location damage folds together with Major Wound effects additively: both are true about the same body at once.

The Major Wound table (1D10)

d10	wound	what it does
1	Concussed	−20% to everything
2	Winded	−20% physical, and you lose your action
3	Bleeding	1 HP at the end of each round
4	Manipulation	−30% manipulation
5	Mobility	−30% physical, MOV halved
6	Deep bleeding	2 HP at the end of each round
7	Sensory	−40% perception, and −40% manipulation (sight) or communication (hearing)
8	Broken	−30% manipulation, or −30% physical and MOV halved
9	Crippling	defence only, MOV 1
10	Catastrophic	unconscious, defence only, MOV 1

Wounds stack: two concussions is −40%, and a Major Wound stacks with a shattered limb, because both are true about the same body. Where a wound splits two ways and the variant was never recorded, the harsher reading applies.

Bleeding

	per round	stopped by
Bleeding	1	a successful First Aid, or Medicine at any difficulty
Deep bleeding	2	a Difficult First Aid, or Medicine at any difficulty

Any one listed stop is enough. First Aid restoring hit points does not clear the wound — the bleed keeps running until something on that list lands.

Panic — the short track

0 to 5, upward, minutes long: what is happening to you now.

	track	penalty
Steady	0	—
Rattled	1	—
Shaken	2	−5%
Losing it	3	−10%
Overwhelmed	4	−20%
Broken	5	−20%, and they break

Talking someone down: a success takes one point off, a special or critical takes two — and a fumble puts one on.

Coherence — the long track

0 to 10, downward, campaign length: what knowing has cost you. Do not confuse the two tracks at the table.

band	from	all rolls	communication
Anchored	8	—	—
Loose	5	—	−5%
Adrift	3	−5%	−10%
Unmoored	1	−10%	−20%, and −30% to the return
Displaced	0	−20%	−30% — permanent

What it costs

Fumbling a crossing	1
Witnessing a paradox	1
Using crossing tech	1
Breaking local law	1
Overstaying	1
Meeting yourself	2
Killing a duplicate	3

Getting it back

One point each: a debrief, a week of downtime, an anchor object.

The way home

The return clock

Three steps. It is the crossing that gets harder, not the people — a cost the players can see coming.

steps	the return is at
0	—
1	−10%
2	−20%, and Difficult
3	−30%, and Difficult

Extraction

roll	completes?	clock
Critical	yes	a step back
Special	yes	—
Success	yes	—
Failure	yes	+1
Fumble	no	+1

Nothing else takes damage from a bad extraction. Getting out badly does not hurt anyone on the causeway; it makes the next crossing harder.

Craft actions — the stations

Every agent takes a station, each uses a skill somebody already has, and the round is one roll each in the normal reaction order. No vector arithmetic, no map — range is a band.

station	skill	does	heat
Helm	Pilot	changes the band	+1
Guns	Energy Weapon	damage	+2, and on a failure too
Sensors	Computer Use	marks a target	—
Engines	Engineering	sheds heat	−3
Damage control	Repair	hull	—
Signals	Persuade	talking	—
Medical	First Aid	the crew	—
Anchor	Transposition	escape	+2

Heat

Runs 0–10. Loud from 4. Blind from 6. Slow from 8.

Space range bands

band	to hit
Docked	0
Knife	+20
Close	+10
Standoff	−10
Distant	−30
Gone	cannot be attempted

The environment

Falling

1d6 per 3 metres, to a maximum of 20 dice — reached at 60 metres, and nothing above that falls harder. Fall damage ignores armour.

Drowning and airlessness

1 point per round. Caught unprepared, you hold your breath half as long.