local Players = game:GetService("Players")
local UserInputService = game:GetService("UserInputService")
local RunService = game:GetService("RunService")

local player = Players.LocalPlayer

-- REPLACEABLE ASSETS
local idleId         = "rbxassetid://98946450554814"
local forwardWalkId  = "rbxassetid://87493540718854"
local backwardWalkId = "rbxassetid://95970874156673"
local sprintAnimId   = "rbxassetid://108891884872744"

-- REPLACEABLE ASSETS FOR ALTERNATIVE ANIMATIONS (50 Health Animations!!)
local altIdleId      = "rbxassetid://90685886162807"
local altWalkId      = "rbxassetid://101924559363550"

local SPRINT_SPEED = 23 -- how fast you can run
local NORMAL_SPEED = 11 -- how fast do you wander
local BACKWARD_SPEED = 8 -- how slow do you want to walk backwards as.
local SPRINT_ANIMATION_SPEED = 3.5 -- Run Animation Speed

local isSprinting = false -- detects if ur sprinting
local isAltMode = false - checks if ur low

local character
local humanoid
local rootPart
local animator

-- Tracks
local idleTrack, forwardTrack, backwardTrack, sprintTrack
local altIdleTrack, altForwardTrack, altBackwardTrack

local heartbeatConn
local speedLoopTask
local currentTrack

local function stopTrack(track, fadeTime)
	if track and track.IsPlaying then
		track:Stop(fadeTime or 0.1)
	end
end

local function playOnly(track, speedOverride)
	if not track then return end

	if currentTrack == track then
		if not track.IsPlaying then
			track:Play(0.1, 1, speedOverride or 1)
		end
		if speedOverride then
			track:AdjustSpeed(speedOverride)
		end
		return
	end

	if currentTrack then
		currentTrack:Stop(0.1)
	end

	currentTrack = track
	track:Play(0.1, 1, speedOverride or 1)

	if speedOverride then
		track:AdjustSpeed(speedOverride)
	end
end

local function makeTrack(animationId, priority, looped)
	if not animationId or animationId == "" then return nil end
	local anim = Instance.new("Animation")
	anim.AnimationId = animationId
	local track = animator:LoadAnimation(anim)
	track.Priority = priority
	track.Looped = looped or false
	return track
end

local function cleanup()
	if heartbeatConn then heartbeatConn:Disconnect() end
	if speedLoopTask then speedLoopTask = nil end

	-- Stop all tracks...
	for _, track in ipairs({idleTrack, forwardTrack, backwardTrack, sprintTrack, altIdleTrack, altForwardTrack, altBackwardTrack}) do
		stopTrack(track, 0)
	end

	idleTrack = nil; forwardTrack = nil; backwardTrack = nil; sprintTrack = nil
	altIdleTrack = nil; altForwardTrack = nil; altBackwardTrack = nil
	currentTrack = nil

	if character then
		local animate = character:FindFirstChild("Animate")
		if animate then animate.Enabled = true end
	end
end

local function getCurrentTracks()
	if isAltMode then
		return altIdleTrack, altForwardTrack, altBackwardTrack or backwardTrack, nil
	else
		return idleTrack, forwardTrack, backwardTrack, sprintTrack
	end
end

local function applyWalkSpeed()
	if not humanoid or not rootPart then return end

	local moveDir = humanoid.MoveDirection
	local moving = moveDir.Magnitude > 0.1

	if isAltMode then
		humanoid.WalkSpeed = NORMAL_SPEED  -- Sprint disabled in alt mode
		return
	end

	if not moving then
		humanoid.WalkSpeed = isSprinting and SPRINT_SPEED or NORMAL_SPEED
		return
	end

	local dot = moveDir:Dot(rootPart.CFrame.LookVector)

	if dot < -0.2 then
		humanoid.WalkSpeed = BACKWARD_SPEED
	elseif isSprinting then
		humanoid.WalkSpeed = SPRINT_SPEED
	else
		humanoid.WalkSpeed = NORMAL_SPEED
	end
end

local function updateAnimations()
	if not humanoid or not rootPart then return end

	local idleT, forwardT, backwardT, sprintT = getCurrentTracks()

	local moveDir = humanoid.MoveDirection
	local moving = moveDir.Magnitude > 0.1

	if not moving then
		playOnly(idleT)
		return
	end

	local dot = moveDir:Dot(rootPart.CFrame.LookVector)

	if dot < -0.2 then
		playOnly(backwardT)
		return
	end

	if not isAltMode and isSprinting and sprintT then
		playOnly(sprintT, SPRINT_ANIMATION_SPEED)
		return
	end

	playOnly(forwardT)
end

local function setupTracks()
	if not animator then return end

	-- Assets Priotries
	idleTrack = makeTrack(idleId, Enum.AnimationPriority.Action, true)
	forwardTrack = makeTrack(forwardWalkId, Enum.AnimationPriority.Action, true)
	backwardTrack = makeTrack(backwardWalkId, Enum.AnimationPriority.Action, true)
	sprintTrack = makeTrack(sprintAnimId, Enum.AnimationPriority.Action4, true)

	-- Alts
	altIdleTrack = makeTrack(altIdleId, Enum.AnimationPriority.Action, true)
	altForwardTrack = makeTrack(altWalkId, Enum.AnimationPriority.Action, true)
	altBackwardTrack = makeTrack(backwardWalkId, Enum.AnimationPriority.Action, true) -- Reuse backward
end

local function setupCharacter(char)
	cleanup()

	character = char
	task.wait(0.2)

	humanoid = character:WaitForChild("Humanoid", 5)
	rootPart = character:WaitForChild("HumanoidRootPart", 5)

	if not humanoid or not rootPart then return end

	animator = humanoid:FindFirstChildOfClass("Animator") or Instance.new("Animator")
	animator.Parent = humanoid

	local animate = character:FindFirstChild("Animate")
	if animate then animate.Enabled = false end

	setupTracks()

	applyWalkSpeed()
	updateAnimations()

	-- checks if you're low
	local healthConn = humanoid.HealthChanged:Connect(function(health)
		if health <= 50 then
			if not isAltMode then
				isAltMode = true
				updateAnimations()
				applyWalkSpeed()
			end
		end
		-- Note: it doesn't go back until you go above health 50
	end)

	speedLoopTask = task.spawn(function()
		while character and character.Parent and humanoid and humanoid.Parent do
			applyWalkSpeed()
			task.wait(0.1)
		end
	end)

	heartbeatConn = RunService.Heartbeat:Connect(function()
		if not character or not character.Parent then return end

		if not isAltMode and isSprinting and sprintTrack and sprintTrack.IsPlaying then
			sprintTrack:AdjustSpeed(SPRINT_ANIMATION_SPEED)
		end

		updateAnimations()
	end)

	-- Cleanup HP connections
	task.spawn(function()
		while character and character.Parent do task.wait(1) end
		if healthConn then healthConn:Disconnect() end
	end)
end

-- Input Handling
UserInputService.InputBegan:Connect(function(input, gameProcessed)
	if gameProcessed then return end

	if input.KeyCode == Enum.KeyCode.L then -- Toggle ALT Anims
		isAltMode = not isAltMode
		applyWalkSpeed()
		updateAnimations()

	elseif input.KeyCode == Enum.KeyCode.X then -- Toggle Sprint, CHANGE THIS..
		if not isAltMode then
			isSprinting = not isSprinting
			applyWalkSpeed()
			updateAnimations()
		end
	end
end)

player.CharacterAdded:Connect(setupCharacter)
player.CharacterRemoving:Connect(cleanup)

if player.Character then
	task.spawn(setupCharacter, player.Character)
end