Hit Location by Depth
Likely rule. Not yet locked, but the leading design and the one everything else should be tested against.
Hit location is rolled on an exploding d6. You cannot reach a critical location without exploding. Each explosion drives the hit one layer deeper into the machine.
The structure falls out of the die
A single exploding d6 partitions itself into exact tiers of five, separated by the unreachable multiples of 6. No table design is required — the die does it.
| Tier | Results | Explosions needed | Each result | Tier total |
|---|---|---|---|---|
| 1 | 1-5 | 0 | 16.667% | 83.333% |
| 2 | 7-11 | 1 | 2.778% | 13.889% |
| 3 | 13-17 | 2 | 0.463% | 2.315% |
| 4 | 19-23 | 3 | 0.077% | 0.386% |
Tier totals form an exact geometric series summing to 1: 5/6, 5/36, 5/216, 5/1296.
The unreachable multiples of 6 are not a defect here — they are the boundaries between layers. What looked like an oddity in the raw distribution becomes the load-bearing feature.
Generated: analysis/exploding-d6.md.
Why this is the right mechanic for this game
It is not merely convenient. It is the same idea as the game's central metaphor, expressed in dice instead of prose.
| Design goal | How depth tiers serve it |
|---|---|
| Layered protection | The brief's whole premise is armor, then structure, then components. The die now models that: outer hits are common, deep hits require punching through |
| Localized degradation | Damage naturally concentrates on the outside and only occasionally reaches something vital, which is how machines actually fail |
| Playable damage | A unit takes many tier-1 hits before anything critical is touched, so it degrades progressively instead of dying to one unlucky roll |
| Critical = critical | An explosion is already the critical mechanic. Now a critical result literally means the shot found something critical. The mechanic and the fiction are the same sentence |
| Bounded bookkeeping | Five entries per tier, and most hits never leave tier 1 |
It also resolves OQ-05 — that a 2d10 bell curve concentrated 44% of hits on a torso and only 5% on weapon-bearing arms, undercutting localized degradation. Depth tiers replace a lateral distribution problem with a depth structure, which is what the game actually wanted.
Template shape
Five entries per tier is a natural template size.
| Tier | Contains | Example for a mech |
|---|---|---|
| 1 | External structure — the parts that exist to be shot | Left arm, right arm, left leg, right leg, torso |
| 2 | Internal systems | Weapon mount, engine, cooling, sensors, ammunition feed |
| 3 | Critical systems | Cockpit, reactor, magazine, gyro, neural link |
| 4 | Catastrophic | Reserved for the genuinely rare |
Each unit type gets its own tier contents. Infantry, tanks, aerospace craft, and capital ships share the structure while differing in what fills it — which serves the unified-resolution goal without forcing a rifleman and a frigate onto the same anatomy.
The open implementation question
Under one-roll resolution, location cannot be a second independent roll. Two ways to honour that:
Option A — the attack roll's own explosions set the depth
The attack roll is the location roll. Explode zero times, hit tier 1; once, tier 2; twice, tier 3.
| For | Perfect one-roll compliance. Ties depth to attack quality: a better hit finds deeper systems, which is both realistic and satisfying. Critical result and critical location become the same event |
| Against | Depth frequency becomes hostage to dice count (OQ-25). At 1d6 a deep hit is 16.7%; at 3d6 at least one die explodes 42% of the time, so deep hits would triple in frequency purely from pool size |
| Needs | A rule for multi-die rolls — longest chain on a single die, or total explosions across the pool. These give very different rates |
Option B — a dedicated location die thrown alongside
A location d6 is thrown with the attack dice and read separately.
| For | Crisp, stable tier probabilities independent of pool size. Depth stays at exactly 83.3 / 13.9 / 2.3 regardless of how OQ-25 resolves |
| Against | Depends on OQ-22 reading "one roll" permissively as one throw rather than one result |
| Needs | OQ-22 resolved |
Leaning: Option A, because coupling depth to attack quality is a feature rather than a compromise, and because it needs no exemption from the one-roll rule.
But the advertised tier shares do not survive Option A. The 83.3 / 13.9 / 2.3 figures are the partition of a single exploding d6. With three dice, the chance at least one explodes is
1 − (5/6)³ = 42.1%, so under Option A deep hits are three times more common than the table above shows, and a "critical" location would be found on roughly two hits in five.That is almost certainly too often for something described as critical. Three ways out: use a dedicated location die (Option B, keeping the clean shares); require the same die to explode repeatedly rather than counting explosions across the pool; or accept the higher rate and redefine what lives in each tier. This must be settled before any armour or component values are set, since it drives how often components are hit at all.
Consequences to watch
| Risk | Note |
|---|---|
| Tier 1 saturation | If 83% of hits land on five external locations, those locations absorb nearly everything. Their Armor Capacity must be sized for that, not for an even spread |
| Deep hits may be too rare | 2.3% for tier 3 means a cockpit hit roughly once every 43 hits. Dramatic, possibly too scarce to shape tactics |
| Called shots | Spending Edges or Margin to buy depth is the obvious lever, and it gives gunnery skill something to purchase. It also risks making the random tier structure irrelevant if priced too cheaply |
| Armor should gate depth | A natural interaction: heavier Threshold could suppress a tier, so a shot that would reach tier 2 is stopped at tier 1. This is the layered-protection metaphor completing itself, and it is worth prototyping early |