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

local player = Players.LocalPlayer

local SPRINT_SPEED = 25.3
local NORMAL_ANIM_ID = "rbxassetid://102724925865450"
local LOW_HEALTH_ANIM_ID = "rbxassetid://92131986088134"
local HEALTH_THRESHOLD = 49

local function setupSprint(char)
	local humanoid = char:WaitForChild("Humanoid")
	local animator = humanoid:WaitForChild("Animator")

	local oldSprint = char:FindFirstChild("Sprint")
	if oldSprint then
		oldSprint:Destroy()
		print("Removed old Sprint script from", char.Name)
	end

	local normalAnim = Instance.new("Animation")
	normalAnim.AnimationId = NORMAL_ANIM_ID
	local normalTrack = animator:LoadAnimation(normalAnim)
	normalTrack.Looped = true

	local lowAnim = Instance.new("Animation")
	lowAnim.AnimationId = LOW_HEALTH_ANIM_ID
	local lowTrack = animator:LoadAnimation(lowAnim)
	lowTrack.Looped = true

	local sprinting = false
	local lowHealthMode = false
	local normalSpeed = humanoid.WalkSpeed

	local function updateAnimation()
		if sprinting then
			if humanoid.Health < HEALTH_THRESHOLD then
				if not lowHealthMode then
					lowHealthMode = true
					normalTrack:Stop()
					lowTrack:Play()
				end
			else
				if lowHealthMode then
					lowHealthMode = false
					lowTrack:Stop()
					normalTrack:Play()
				end
			end
		end
	end

	local function startSprint()
		if not sprinting then
			sprinting = true
			humanoid.WalkSpeed = SPRINT_SPEED
			updateAnimation()
		end
	end

	local function stopSprint()
		if sprinting then
			sprinting = false
			humanoid.WalkSpeed = normalSpeed
			normalTrack:Stop()
			lowTrack:Stop()
		end
	end

	UserInputService.InputBegan:Connect(function(input, processed)
		if not processed and input.KeyCode == Enum.KeyCode.LeftShift then
			startSprint()
		end
	end)

	UserInputService.InputEnded:Connect(function(input)
		if input.KeyCode == Enum.KeyCode.LeftShift then
			stopSprint()
		end
	end)

	humanoid.HealthChanged:Connect(function()
		updateAnimation()
	end)

	RunService.RenderStepped:Connect(function()
		if sprinting then
			if humanoid.Health < HEALTH_THRESHOLD then
				if not lowTrack.IsPlaying then
					lowTrack:Play()
				end
			else
				if not normalTrack.IsPlaying then
					normalTrack:Play()
				end
			end
		end
	end)
end

if player.Character then
	setupSprint(player.Character)
end

player.CharacterAdded:Connect(function(char)
	setupSprint(char)
end)