Build a Tower

Lesson 6 of 18 in Coddy's Roblox Game: Tower Defense course.

Now the player's side. DefenseClient is a LocalScript inside the HUD, a ScreenGui Roblox copies onto each player's screen. The HUD's Shop frame holds a TextButton per tower, named after it. A button's Activated event fires when it is clicked or tapped:

button.Activated:Connect(function()
	selected = button.Name
end)

Then a click on one of the grey pads builds the chosen tower there. The client reads the click from the mouse (me:GetMouse(), its Button1Down event and its Target, the part under the pointer), but it cannot build anything itself: towers live on the server. It asks through the RemoteEvent Remotes.Place:

-- client
remotes.Place:FireServer(pad, "Archer")
-- server: Roblox adds the player first
remotes.Place.OnServerEvent:Connect(function(player, pad, kind)
end)

The tower models wait in ServerStorage.Towers; the server clones one onto the pad.

Challenge

Medium

In DefenseClient:

Get Players, Settings (with WaitForChild), local remotes = game.ReplicatedStorage:WaitForChild("Remotes"), local me = Players.LocalPlayer and local hud = script.Parent.
For each TextButton in hud.Shop, set its text to the tower's name and price (Archer $60), and on Activated remember it in selected.
On the mouse's Button1Down, if the target is in workspace.Pads and a tower is selected, fire remotes.Place with the pad and the tower's name.

In DefenseServer: add local remotes and local towers = workspace.Towers, write placeTower(pad, kind) (clone, PivotTo the pad's CFrame raised by half the pad's height plus 1, parent to towers), and connect remotes.Place.OnServerEvent to it.

Press Play, pick a tower and click a pad. Then Check.

Try it yourself

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

local enemies = workspace.Enemies

print("The base can take " .. Settings.BaseHealth .. " hits")

-- The waypoints, in order (they are named 1, 2, 3...)
local waypoints = workspace.Path.Waypoints:GetChildren()
table.sort(waypoints, function(a, b)
	return tonumber(a.Name) < tonumber(b.Name)
end)

-- The base's health, as an attribute of the workspace: every client can read it
workspace:SetAttribute("BaseHealth", Settings.BaseHealth)

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

	local money = Instance.new("IntValue")
	money.Name = "Money"
	money.Value = Settings.StartMoney
	money.Parent = leaderstats
end)

-- An enemy reached the base
local function damageBase(amount)
	local health = math.max(0, workspace:GetAttribute("BaseHealth") - amount)
	workspace:SetAttribute("BaseHealth", health)
end

-- Walk an enemy along the path. MoveTo gives up after 8 seconds and says so
-- (MoveToFinished with false), so a slow enemy is sent again until it arrives.
local function walkPath(enemy)
	local humanoid = enemy.Humanoid
	for i = 2, #waypoints do
		repeat
			humanoid:MoveTo(waypoints[i].Position)
		until humanoid.MoveToFinished:Wait() or not enemy.Parent
		if not enemy.Parent then
			return
		end
	end
	-- it reached the base
	damageBase(Settings.Enemies[enemy.Name].Damage)
	enemy:Destroy()
end

-- A new enemy at the gate, walking the path
local function spawnEnemy(kind)
	local enemy = ServerStorage.Enemies[kind]:Clone()
	-- dropped in just above the first waypoint
	enemy:PivotTo(waypoints[1].CFrame + Vector3.new(0, 5, 0))
	local info = Settings.Enemies[kind]
	enemy.Humanoid.MaxHealth = info.Health
	enemy.Humanoid.Health = info.Health
	enemy.Humanoid.WalkSpeed = info.Speed
	enemy.Parent = enemies
	task.spawn(walkPath, enemy)
	return enemy
end

-- One wave: its enemies one by one, then wait until they are all gone
local function runWave(list)
	for _, kind in list do
		spawnEnemy(kind)
		task.wait(Settings.SpawnGap)
	end
	while #enemies:GetChildren() > 0 do
		task.wait(0.2)
	end
end

-- The waves, each after a break
for i, list in Settings.Waves do
	task.wait(Settings.WaveBreak)
	runWave(list)
end