"Make me a mat that needs to detect 2 people which enables a billboard GUI counting down from 5 seconds if a person steps off the mat it breaks the billboard gui and makes it dissappear if they step back on it counts down again after the 5 seconds the 2 players need to teleport to 2 parts of the mat"

-- server script 
local mat = game.Workspace.Mat
local teleportPart1 = game.Workspace.TeleportPart1
local teleportPart2 = game.Workspace.TeleportPart2
local playersOnMat = {}

local function checkPlayers()
	if #playersOnMat == 2 then
		local billboardGui = Instance.new("BillboardGui")
		local textLabel = Instance.new("TextLabel")
		billboardGui.Parent = mat
		textLabel.Parent = billboardGui
		for i=5, 0, -1 do
			textLabel.Text = tostring(i)
			wait(1)
		end
		playersOnMat[1].Character.HumanoidRootPart.CFrame = teleportPart1.CFrame
		playersOnMat[2].Character.HumanoidRootPart.CFrame = teleportPart2.CFrame
		billboardGui:Destroy()
		playersOnMat = {}
	end
end

local function playerEnterMat(otherPart)
	local player = game.Players:GetPlayerFromCharacter(otherPart.Parent)
	if player then
		table.insert(playersOnMat, player)
		checkPlayers()
	end
end

local function playerLeaveMat(otherPart)
	local player = game.Players:GetPlayerFromCharacter(otherPart.Parent)
	if player then
		for i, v in ipairs(playersOnMat) do
			if v == player then
				table.remove(playersOnMat, i)
				if mat:FindFirstChild("BillboardGui") then
					mat.BillboardGui:Destroy()
				end
			end
		end
	end
end

mat.Touched:Connect(playerEnterMat)
mat.TouchEnded:Connect(playerLeaveMat)