Status Effects — damage and change over time

What it is. Conditions that persist: poison ticking each turn, a burn, a shield, a slow, a rage buff. Status turns a hit from a one-frame event into a state you carry — the layer that lets system-build-diversity and system-counter-systems interact instead of just stacking flat numbers.

Player fantasy / why it’s fun. Setting up. The poison you stacked three turns ago finally kills; the shield you pre-cast eats the boss’s big hit. Status rewards plans, not just reactions — it’s the memory of combat.

When to use / when NOT

Use status when…	Skip when…
You want set-up-then-payoff play	Combat is pure twitch reaction
Builds should interact (a synergy engine)	You have < ~4 effects (just make them direct)
Counters need a vocabulary (cleanse, resist)	Legibility budget is already spent

Every status is a rule the player must hold in their head. Ship the fewest that carry the most interaction — a bloated status list is unreadable, not deep.

Variants

Kind	Shape	Stacking	Example
DoT (poison, burn)	damage per tick, N ticks	intensity or duration	Slay the Spire poison (−1/turn, decays)
Debuff (slow, weak, vuln)	multiplier on the target	usually duration	weak = −25% dmg dealt
Buff (rage, haste, shield)	multiplier / absorb on self	intensity or refresh	block that expires next turn
CC (stun, freeze, root)	skips/limits actions	rarely stacks; diminishing	one turn skipped
Trigger (mark, curse)	fires on a condition	count-based	”next hit crits”

Stacking rules — pick one per effect, state it

Rule	Behaviour	Good for
Intensity	more applications = bigger effect	poison, bleed
Duration	more applications = longer, same size	slow, weak
Refresh	re-apply resets the timer, no stack	most buffs
Independent	each application is its own timer	rare; hard to read
Cap	stacks up to N, then no-op	keep any of the above bounded

Ambiguous stacking is the #1 status bug. Decide intensity-vs-duration per effect and cap it — an uncapped intensity DoT trivializes the game (FUN.md law 3).

Tuning levers

Lever	Does	Healthy range
Tick timing	when DoT resolves	fixed point in the turn/second; deterministic
Decay	how stacks fall off	poison −1/turn keeps it self-limiting
Cap	max stacks/intensity	always set one
Cleanse cost	price to remove a status	real, so statuses are a threat not a nuisance
Duration	turns/seconds it lasts	long enough to matter, short enough to plan around

How it wires to Hayao

Status is pure state on the entity in world.state — a { id, stacks, turns } list, resolved by a pure tick function; all rolls via world.rng. That makes clone-and-score bots free (FUN.md law 7): pilot the intended build, assert it beats the null build (FUN.md law 2, §11 draft-delta).
Legibility is intent honesty. A shown “poison 6” must deal exactly 6 over its ticks (FUN.md §11 — resolve the telegraph, compare to the number). Audit it.
The tick returns choreography — the number pop and tint are cosmetic (FloatingText, FLOAT_PRESETS; JUICE Part 1), out of world.hash().
No special engine primitive is needed — status is your data. Grep docs/API.md before citing; there is no applyStatus in the surface, and there shouldn’t be.

Fails when…

Uncapped intensity. One infinite-scaling DoT becomes the only strategy (dominant, system-build-diversity collapses).
Illegible stacking. The player can’t predict the tick, so they stop planning — status becomes noise, not depth.
No counter-play. A status with no cleanse/resist and a long duration is just unfair; give the vocabulary a full loop (system-counter-systems).
Silent resolution. Ticks with no pop/tint read as HP randomly draining. Answer on ≥ 2 senses (JUICE).

Verify

FUN.md §11 — draft/build delta (the status build beats the null build); intent honesty (shown status == resolved damage).
FUN.md law 3 — the cap inequality asserted against config.
Determinism: golden hash of a scripted fight with statuses; view-on == view-off.
Feel: number pops answer on ≥ 2 senses → JUICE.md Part 3.

Composes with

system-combat-model — status is damage/change that resolves over the model’s clock.
system-counter-systems — cleanse/resist/immunity are the counter vocabulary.
system-build-diversity — status synergies are a primary source of viable builds.
system-telegraphs — a big incoming debuff should itself telegraph.