-- LocalScript in StarterPlayerScripts

local Players = game:GetService("Players")
local RunService = game:GetService("RunService")
local player = Players.LocalPlayer

-- Wait for character and parts
local character = player.Character or player.CharacterAdded:Wait()
local humanoid = character:WaitForChild("Humanoid")
local rootPart = character:WaitForChild("HumanoidRootPart")

-- Wait until character is likely grounded
repeat task.wait() until rootPart.Velocity.Magnitude < 1

-- Freeze movement
humanoid.PlatformStand = true

-- Settings
local amplitude = 10 -- height
local speed = 10 -- bounce speed
local startPosition = rootPart.Position -- should now be correct

-- Bouncing
RunService.RenderStepped:Connect(function()
	if rootPart and rootPart.Parent then
		local bounceY = math.sin(tick() * speed) * amplitude
		local newPosition = Vector3.new(startPosition.X, startPosition.Y + bounceY, startPosition.Z)

		rootPart.Velocity = Vector3.zero
		rootPart.RotVelocity = Vector3.zero
		rootPart.CFrame = CFrame.new(newPosition)
	end
end)