SprintScript

--Speed values
local sprintSpeed = 30
local defaultSpeed = 16

--Camera FOV values
local defaultFOV = 70
local fovMultiplier = 0.1

--Streaks particles settings
local windStreaksMinimumSpeed = 20
local windStreaksMinimumRate = 1500

--Sprinting buttons
local sprintInputs = {Enum.KeyCode.LeftControl, Enum.KeyCode.LeftShift}

--Sprint toggle enabled or not
local toggle = false


local cas = game:GetService("ContextActionService")

local camera = workspace.CurrentCamera

local character = game.Players.LocalPlayer.Character or game.Players.LocalPlayer.CharacterAdded:Wait()
local humanoid = character:WaitForChild("Humanoid")

local windStreaks = camera:FindFirstChild(character.Name .. "'s wind streaks") or game.ReplicatedStorage:FindFirstChild(character.Name .. "'s wind streaks") or game.ReplicatedStorage:WaitForChild("SprintReplicatedStorage"):WaitForChild("StreaksPart"):Clone()
windStreaks.Name = character.Name .. "'s wind streaks"


function lerp(a, b, t)
    return a + (b - a) * t
end


function sprintAction(actionName, inputState, inputObject)

    if actionName == "SPRINT" then

        if inputState == Enum.UserInputState.Begin then

            if toggle then
                humanoid.WalkSpeed = humanoid.WalkSpeed == defaultSpeed and sprintSpeed or defaultSpeed

            else
                humanoid.WalkSpeed = sprintSpeed
            end

        elseif inputState == Enum.UserInputState.End then
            if not toggle then
                humanoid.WalkSpeed = defaultSpeed
            end
        end
    end
end

cas:BindAction("SPRINT", sprintAction, true, unpack(sprintInputs))



function handleWindStreaks()

    local currentFOV = camera.FieldOfView

    if (humanoid.WalkSpeed > defaultSpeed and humanoid.MoveDirection.Magnitude > 0) then

        local goalFOV = (humanoid.WalkSpeed / defaultSpeed) * defaultFOV
        goalFOV = defaultFOV + ((goalFOV - defaultFOV) * fovMultiplier)

        camera.FieldOfView = lerp(currentFOV, goalFOV, 0.2)

    else
        camera.FieldOfView = lerp(currentFOV, defaultFOV, 0.2)
    end

    if (humanoid.WalkSpeed >= windStreaksMinimumSpeed and humanoid.MoveDirection.Magnitude > 0) then

        windStreaks.CFrame = camera.CFrame + camera.CFrame.LookVector * (13 / (camera.FieldOfView / defaultFOV))

        windStreaks.Attachment.ParticleEmitter.Rate = (humanoid.WalkSpeed / windStreaksMinimumSpeed) * windStreaksMinimumRate

        windStreaks.Parent = camera

    else
        windStreaks.Parent = game.ReplicatedStorage
    end
end

game:GetService("RunService").RenderStepped:Connect(handleWindStreaks)