Combat Model — the shape of a hit

What it is. The resolution rule underneath every fight: the function that turns attacker + defender + context into a number and a moment. Pick it before you design a single enemy — the model decides whether combat is read-and-react, plan-and-commit, or math-and-optimize, and every other combat system (system-telegraphs, system-status-effects, system-counter-systems) hangs off it.

Player fantasy / why it’s fun. A hit that lands — weight, consequence, a clean line from your input to the enemy’s flinch. Fun combat is legible cause and effect; the model is where that legibility is either won or lost.

When to use / when NOT

Use a formal combat model when…	Skip / simplify when…
Damage varies by matchup, position, or state	One-hit-kill or binary contact (a pure platformer)
The player makes per-hit decisions	Combat is a garnish, not a pillar
You need counters, statuses, or crits to interact	The “fight” is really a puzzle (`genre-grid-puzzle`)

Don’t bolt a deep damage formula onto a game whose fun is elsewhere. A Celeste-like spike is contact → death; that is the model, and it’s correct.

Variants

Model	Clock	Damage shape	Anchor	Feels like
Real-time reactive	frames	fixed per-hit, telegraph-gated	`anchor-shadow-of-mordor`, Zelda	read the tell, punish the gap
Real-time attrition	frames	many small ticks, DPS math	`anchor-vampire-survivors`	the tide vs your build
Turn-based deterministic	turns	shown = resolved, no rolls	`anchor-into-the-breach`	perfect-information chess
Turn-based stochastic	turns	dice / hit-chance	XCOM, roguelikes	budgeted luck, hedged plays
Deckbuilt	turns	numbers from cards + scaling	`anchor-slay-the-spire`	the deck is the weapon
Combo / string	frames	escalating multipliers per chain	`anchor-hades`, brawlers	flow and cancels

Blends are normal: Hades is reactive + combo; Slay the Spire is deckbuilt + deterministic. Satisfy each parent’s verify pattern (process-composition).

Tuning levers

Lever	Does	Healthy range
Time-to-kill (TTK)	hits to drop a basic foe	2–5 for reactive; the whole session for attrition
Time-to-death (TTD)	hits you survive	≥ 2 before a wound; instadeath only with heavy telegraph
Hit-stop	freeze on impact — the weight	3–8 frames; > 12 reads as a hitch (JUICE Part 2)
i-frames	invulnerable window after a hit	specced in frames, proven edge-in/edge-out
Variance	roll spread (stochastic only)	tight enough that plans hold; ≤ ±15% or shown-as-chance
Crit rate / mult	spike layer	rare + big, or frequent + small — not both

Derive TTK/TTD from the fight length you want, not by eyeballing (FUN.md law 3).

How it wires to Hayao

Pure resolution. Combat is a function over world.state; all rolls through world.rng. The sim resolves instantly and returns choreography for the view to replay (FUN.md law 6) — hit-stop and flash are cosmetic, never in world.hash().
Reactive combat is telegraph-gated. Every threat activation is preceded by a tell; prove it with telegraphIssues(timeline, minFrames). See system-telegraphs.
Feel is a contract. Declare a FeedbackContract (in @hayao) for hit, land, death; gate hit-stop/shake with feedbackIssues (design/JUICE.md Part 3).
Turn-based reuses the real-time stack — an input edge is one world step (FUN.md §10). Pure state gives clone-and-score bots for free: run the intended line vs a null line and assert the gap (FUN.md law 2).
Reference wiring: examples/small-flame for reactive feel; the top-down §4 pattern for hit-stop + i-frames buffering inputs through the freeze.

Fails when…

Hit-stop eats inputs. A freeze that doesn’t buffer intent across it makes attacks “randomly” vanish (FUN.md §4). Any pause must re-emit buffered input.
TTK too low both ways. If you and the foe both die in one hit, there’s no combat — there’s a coin flip. Give the loop room to be a loop.
Variance drowns skill. Big rolls on top of a reactive read punish the correct play. If it’s stochastic, show the chance (intent honesty, FUN.md §11/§12).
Damage numbers with no resolution moment. A number that ticks with no impact frame reads as a spreadsheet, not a hit. Answer every hit on ≥ 2 senses (JUICE).

Verify

Reactive: kiting-bot telemetry — win time, hp floor, 0 deaths; every threat telegraphed → FUN.md §4, telegraphIssues.
Skill-delta: intended combat beats null (do-nothing / flail) by a margin → FUN.md law 2.
Feel: feedbackIssues for hit/death; hit-stop ≤ 12 frames → JUICE.md Part 3, VERIFICATION Channel 4.
Determinism: golden hash of a scripted fight; view-on == view-off hash.

Composes with

system-telegraphs — reactive combat is only fair if threats announce; the telegraph is half the model.
system-status-effects — DoT/buffs/debuffs are damage that resolves over time; they layer on the resolution rule.
system-counter-systems — the matchup table that makes one hit mean more.
system-grace — i-frames, hit-stop buffering, wound-before-death live here.
system-boss-design — a boss is a combat model with phases and spectacle.