AirStrafe.lua

local RunService = game:GetService("RunService")

local char = script.Parent
local humanoid = char:WaitForChild("Humanoid")

local rootPart = humanoid.RootPart
local XZ_VECTOR3 = Vector3.new(1, 0, 1)

local lastCF = CFrame.new()
local airAccel = 0

local function stepPhysics()
	local state = humanoid:GetState()
	
	local cframe = rootPart.CFrame
	local rotation = cframe - cframe.Position
	
	local deltaCF = rotation:ToObjectSpace(lastCF)
	lastCF = rotation
	
	if state.Name ~= "Freefall" then
		airAccel = 0
		return
	end
	
	local activeForce = (rootPart.Velocity * XZ_VECTOR3).Magnitude
	
	if activeForce > airAccel then
		airAccel = activeForce
	elseif activeForce < airAccel then
		local ratio = airAccel / activeForce
		local apply = Vector3.new(ratio, 1, ratio)
		rootPart.Velocity = rootPart.Velocity * apply
	end
	
	rootPart.Velocity = deltaCF:VectorToObjectSpace(rootPart.Velocity) + humanoid.MoveDirection
end

RunService.Heartbeat:Connect(stepPhysics)