Characters and animation

Character basics

• A player character is a Model with a Humanoid, HumanoidRootPart (the root; move the character with character:PivotTo(cframe)), R15 body parts, and an Animate LocalScript.
• Defaults (walk speed, jump, health, R6/R15, collisions, body scaling) are configured in Studio's Avatar Settings window and StarterPlayer (CharacterWalkSpeed, CharacterJumpHeight or CharacterUseJumpPower + CharacterJumpPower).
• Custom character: put a Model named StarterCharacter in StarterPlayer. Custom per-player spawns: Players.CharacterAutoLoads = false, then player:LoadCharacterAsync() when ready (e.g. after data loads). LoadCharacter (non-Async) is deprecated.
• Characters are destroyed and recreated on death/respawn: bind per-character logic in CharacterAdded.
• Client-set WalkSpeed/JumpHeight are trivially exploitable; enforce limits on the server or use server authority (roblox-security, roblox-physics).

Health and damage (server)

--!strict
local Players = game:GetService("Players")

local function damage(target: Model, amount: number, source: Player?)
	local humanoid = target:FindFirstChildOfClass("Humanoid")
	if not humanoid or humanoid.Health <= 0 then
		return
	end
	humanoid:SetAttribute("LastDamagedBy", if source then source.UserId else 0)
	humanoid:TakeDamage(amount) -- respects ForceField; use Health -= amount to bypass
end

Players.PlayerAdded:Connect(function(player)
	player.CharacterAdded:Connect(function(character)
		local humanoid = character:WaitForChild("Humanoid") :: Humanoid
		humanoid.MaxHealth = 150
		humanoid.Health = 150
		humanoid.Died:Once(function()
			local killerId = humanoid:GetAttribute("LastDamagedBy")
			print(`{player.Name} died (killer {killerId})`)
		end)
	end)
end)

return damage

• Disable default regen by deleting/replacing the Health script via StarterCharacterScripts.
• Humanoid.BreakJointsOnDeath = false + ragdoll constraints for ragdolls.
• States: humanoid:ChangeState(Enum.HumanoidStateType.Jumping), SetStateEnabled(state, false), StateChanged. MoveDirection, FloorMaterial, RootPart, SeatPart are read-only helpers.
• humanoid:MoveTo(position) walks NPCs (times out after 8 s; re-issue for long paths — see roblox-npc-ai).

Appearance

--!strict
local Players = game:GetService("Players")

local function applyUniform(player: Player)
	local character = player.Character
	local humanoid = character and character:FindFirstChildOfClass("Humanoid")
	if not humanoid then
		return
	end
	local ok, description = pcall(function()
		return Players:GetHumanoidDescriptionFromUserIdAsync(player.UserId)
	end)
	if not ok then
		return
	end
	description.Shirt = 123456 -- asset ids
	description.Pants = 654321
	description.HeightScale = 1.05
	pcall(function()
		humanoid:ApplyDescriptionAsync(description) -- server-side; replicates
	end)
end

return applyUniform

Player:LoadCharacterWithHumanoidDescriptionAsync(description) spawns directly with an outfit. All the non-Async variants (ApplyDescription, GetHumanoidDescriptionFromUserId, ...) are deprecated.

Animation playback

--!strict
local function playAttack(character: Model, animation: Animation): AnimationTrack?
	local humanoid = character:FindFirstChildOfClass("Humanoid")
	local animator = humanoid and humanoid:FindFirstChildOfClass("Animator")
	if not animator then
		return nil
	end
	local track = animator:LoadAnimation(animation) -- Humanoid:LoadAnimation is deprecated
	track.Priority = Enum.AnimationPriority.Action
	track.Looped = false
	track:GetMarkerReachedSignal("Hit"):Connect(function(param)
		print("hit frame reached", param) -- apply damage window, play sound, etc.
	end)
	track:Play(0.1) -- fade time
	return track
end

return playAttack

• Where to play: the local player's own character → play on the client (replicates automatically via its Animator); NPCs → play on the server (or on clients for purely cosmetic, high-count NPCs).
• Load each Animation once per Animator and reuse the track; don't call LoadAnimation every time an action happens (there's a per-Animator track limit). Exception: server authority (query live tracks).
• Priorities: Core < Idle < Movement < Action < Action2 < Action3 < Action4. Blend with AdjustWeight, change speed with AdjustSpeed, stop with Stop(fadeTime).
• Events: track.Stopped, track.Ended, markers via GetMarkerReachedSignal (KeyframeReached is superseded).
• Animation assets must be owned by (or shared with, via asset permissions) the experience's owner — otherwise they silently fail to play in live servers.
• Replace defaults by editing the Animate script's StringValue/Animation children (animate.run.RunAnim.AnimationId) on CharacterAdded, or ship a custom Animate in StarterCharacterScripts.
• Procedural: IKControl (look-at, foot planting, reaching) instead of hand-written joint math.

Tweening

--!strict
local TweenService = game:GetService("TweenService")

local door = Instance.new("Part")
door.Anchored = true
door.Parent = workspace

local info = TweenInfo.new(0.6, Enum.EasingStyle.Quad, Enum.EasingDirection.Out)
local open = TweenService:Create(door, info, { CFrame = door.CFrame * CFrame.new(0, 8, 0) })
open.Completed:Once(function(state)
	print("door tween finished:", state)
end)
open:Play()

• Tween anchored parts or UI. For unanchored/physics objects use constraints.
• Tweening on the server replicates every frame and stutters: for visual-only motion, tween on each client (the server sets the final state or an attribute clients react to).
• Models: tween a CFrameValue and call model:PivotTo(value) in its Changed handler, or tween the primary part with the rest welded to it.
• TweenService:GetValue(alpha, style, direction) for custom interpolation; SmoothDamp for follow motion.

Tools

Tool in StarterPack/Backpack with a Handle part (or RequiresHandle = false). Equipped, Unequipped, Activated fire on both client and server (Activated comes from the client: validate rate and state on the server). Keep weapon logic in modules and use tags rather than scripts inside every tool clone.

Character Controller Library (beta)

Roblox's CCL (require("@rbx/AvatarAbilities")) replaces the fixed Humanoid state machine with composable abilities (Running, Jumping, Climbing, custom Dash...) coordinated by labels, sensors, conditions (StartsWhen/RunsWhile with All/Any/Not), conflicts (Blocks/Stops/Suspends), and lifecycle callbacks. Enable it via File → Beta Features and Avatar Settings → Movement → Abilities. Only use it when the project has opted in; APIs may change while in beta. Sketch: references/character-controller-library.md.

Related skills

roblox-npc-ai (NPC movement), roblox-physics (ragdolls, knockback), roblox-input (ability inputs), roblox-security (movement/damage validation), roblox-game-systems (combat).