Sliding Lasers

Lesson 8 of 18 in Coddy's Roblox Game: Endless Tower course.

The Lasers stage has two red walls, tagged Slider and Kill, that slide across the walkway and back. Each carries an attribute, Slide, a Vector3 saying where it goes from where it starts.

A tween can repeat. TweenInfo.new takes the time, the easing, a direction, how many times to repeat (-1 means forever) and whether to play back in reverse:

local info = TweenInfo.new(2.5, Enum.EasingStyle.Linear, Enum.EasingDirection.InOut, -1, true)
TweenService:Create(part, info, { Position = part.Position + part:GetAttribute("Slide") }):Play()

Linear keeps the speed even, so a player can judge it. The default easing slows at each end, which looks smooth but is hard to time.

Challenge

Medium

Near the top, get TweenService.
Write makeSlide(part): tween the part's Position to its Position plus its Slide attribute, taking Settings.SlideTime seconds, Linear, repeating forever and reversing.
In setupStage, call it for every part tagged Slider.

Press Play and slip past the lasers. Then Check.

Try it yourself

local Players = game:GetService("Players")
local ServerStorage = game:GetService("ServerStorage")
local CollectionService = game:GetService("CollectionService")
local RunService = game:GetService("RunService")
local Settings = require(game.ReplicatedStorage.Settings)

local stages = ServerStorage.Stages
local tower = nil

print("Each tower has " .. Settings.StageCount .. " stages")

-- Every player gets Wins on the leaderboard
Players.PlayerAdded:Connect(function(player)
	local leaderstats = Instance.new("Folder")
	leaderstats.Name = "leaderstats"
	leaderstats.Parent = player

	local wins = Instance.new("IntValue")
	wins.Name = "Wins"
	wins.Parent = leaderstats
end)

-- Anything tagged Kill ends a life
local function killOnTouch(hit)
	local humanoid = hit.Parent:FindFirstChild("Humanoid")
	if humanoid then
		humanoid.Health = 0
	end
end

-- A vanishing step fades soon after someone lands on it, then comes back
local function makeVanish(part)
	part.Touched:Connect(function(hit)
		if part:GetAttribute("Gone") or not hit.Parent:FindFirstChild("Humanoid") then
			return
		end
		part:SetAttribute("Gone", true)
		task.wait(Settings.VanishDelay)
		part.Transparency = 0.8
		part.CanCollide = false
		task.wait(Settings.VanishTime)
		part.Transparency = 0
		part.CanCollide = true
		part:SetAttribute("Gone", nil)
	end)
end

-- Spinners turn a little every frame
RunService.Heartbeat:Connect(function(dt)
	for _, spinner in CollectionService:GetTagged("Spinner") do
		if spinner:IsDescendantOf(workspace) then
			spinner:PivotTo(spinner:GetPivot() * CFrame.Angles(0, math.rad(Settings.SpinSpeed) * dt, 0))
		end
	end
end)

-- Turn on every obstacle in a stage, by its tags
local function setupStage(stage)
	for _, part in stage:GetDescendants() do
		if part:HasTag("Kill") then
			part.Touched:Connect(killOnTouch)
		end
		if part:HasTag("Vanish") then
			makeVanish(part)
		end
		if part:HasTag("Conveyor") then
			part.AssemblyLinearVelocity = part.CFrame.LookVector * Settings.BeltSpeed
		end
	end
end

-- Any stage, at random
local function pickStage()
	local all = stages:GetChildren()
	return all[math.random(1, #all)]
end

-- Put a copy of a model on top of the tower; returns the copy and the new top
local function stack(template, bottom)
	local copy = template:Clone()
	local box, size = copy:GetBoundingBox()
	local lift = bottom - (box.Position.Y - size.Y / 2)
	copy:PivotTo(copy:GetPivot() + Vector3.new(0, lift, 0))
	copy.Parent = tower
	return copy, bottom + size.Y
end

-- Build a new random tower, bottom up
local function buildTower()
	tower = Instance.new("Model")
	tower.Name = "Tower"
	tower.Parent = workspace
	local top = 0
	for i = 1, Settings.StageCount do
		local stage, newTop = stack(pickStage(), top)
		top = newTop
		setupStage(stage)
	end
	stack(ServerStorage.Finish, top)
end

buildTower()