aiKit.fsm — a small finite state machine for NPC brains. local FSM = require("aiKit.fsm") local def = FSM.define("door", { initial = "closed", states = { closed = { update = function(ctx, dt) if ctx.knock then return "open" end end }, open = { enter = function(ctx) ctx.timer = 3 end, update = function(ctx, dt) ctx.timer -= dt; if ctx.timer <= 0 then return "closed" end end, exit = function(ctx) end, }, }, -- checked before the current state's update, in order; `from` = "*" means any state transitions = { { from = "*", to = "closed", when = function(ctx) return ctx.broken end } }, }) local m = FSM.new(def, ctx) m:update(dt) -- runs transitions, then the state's update; a returned name switches state m:go("open", "why") -- switch from outside print(m.state, m.time) -- current state, seconds in it A state's `update` may return a state name (switch), or a name and a reason. `enter(ctx, from, reason)` and `exit(ctx, to)` run on every switch. Unknown state names are errors, so a typo never silently does nothing.