How to make a tower defense game in Roblox Studio

What makes a tower defense game work

The loop in one line: place towers, watch the wave, earn cash, upgrade, survive the next wave. Roblox describes its Tower Defense subgenre (under Strategy) as games where players position defensive units along a path to stop waves of enemies reaching the end of it. The interesting part is the word "strategically".

• Every 10 seconds: a small decision. Save for the upgrade or place another cheap tower now? Sell the tower in the wrong spot?
• Every wave: a question. A fast wave, an armoured wave, a hidden wave, a boss. Each asks whether your defence covers it. When the answer is no, the player learns something.
• Every match: a plan. The map, the difficulty and the towers you brought decide the strategy. A match that ends in a close win is the one players remember.
• Every session: progress. Unlocking a new tower or clearing a harder mode. A common structure is a lobby where players pick a loadout of towers before each match.
• Co-op. Several players defending one path, each placing their own towers, turns strategy into conversation. Shared cash rules (each player earns their own, or a split) shape how friendly a match feels.

Tower defense games that get abandoned usually have one dominant tower that makes the rest pointless, waves that only grow in health so every match plays the same, or a path so short that placement barely matters. If spamming one tower wins, the game is solved and players leave.

Paths, tower roles and enemy types

Design these three together, because each one only matters in relation to the others.

Paths: a long path with turns gives towers more time on each enemy and gives players real choices about where to stand. Corners are natural kill zones, because a tower near a corner covers two stretches of path. A map with two paths that merge forces players to split their defence. Mark where towers can and cannot go (on the path, inside walls) and enforce it on the server.

Waves: alternate the question. A good early sequence is a basic wave, a fast wave, a group wave, then a first boss. Keep a table of every wave's enemy count, health and speed in one ModuleScript so you can balance by editing numbers, not code.

The systems a tower defense game needs

Placement is where tower defense games get exploited. The client shows a ghost tower under the mouse and sends the position. The server checks the player has the cash, that the spot is on a valid placement area, that it is within the map, and that no tower or path is already there. A box query with workspace:GetPartBoundsInBox at the requested spot finds anything in the way; note that it tests bounding boxes, so round towers count as boxes.

Build plan: from a baseplate to launch

1. The path. A Waypoints folder with parts named 1, 2, 3 and so on along a winding road, the first at the spawn and the last at your base. Make them invisible and non-colliding once it works.
2. Enemies and waves. Add the Enemies module and the Waves script. Watch three waves walk the path and drain the base.
3. Towers. Place three tower parts by hand, tag them Tower, set Range, Damage and Cooldown attributes, and add the Towers script. Tune numbers until wave 3 is a near loss.
4. Placement and cash. A Cash value in leaderstats, a tower bar on screen, a ghost preview on the client, and a server function that validates and places the tower. Set each placed tower's OwnerId attribute to the player's UserId so kills pay them.
5. Greybox playable: 3 towers, 10 waves, one map. Play it alone and with two friends. If someone wins without changing strategy, a tower is too strong.
6. Upgrades and sell. Each tower gets two or three upgrade levels that raise its numbers or change its role. Selling returns part of the cost, so mistakes are recoverable.
7. Lobby, loadouts and saving. A lobby to pick towers and a map, matches in separate servers, and saved tower unlocks.
8. Launch features. Enemy health bars, a wave counter and timer, a boss wave with a health bar, a second map or difficulty, and one or two passes.

Enemies that walk the path

Enemies here are anchored parts moved by the server, not characters with Humanoids. The server keeps how far each one has walked in studs, which is exactly the number towers need to decide who is "first". A ModuleScript holds the list so the tower and wave scripts read the same enemies.

-- ModuleScript in ServerScriptService named Enemies.
-- Moves every enemy along the numbered parts in Workspace.Waypoints and
-- keeps the list towers read from. Requiring it starts the movement.
local RunService = game:GetService("RunService")

export type Enemy = { part: BasePart, health: number, speed: number, distance: number, reward: number }

local Enemies = { alive = {} :: { Enemy }, baseHealth = 100 }

local folder = workspace:WaitForChild("Waypoints") :: Folder
local points: { Vector3 } = {}
for i = 1, #folder:GetChildren() do
	local p = folder:WaitForChild(tostring(i)) :: BasePart
	points[i] = p.Position
end

-- Where an enemy is after walking this many studs along the path (nil = at the end)
local function placeAt(distance: number): CFrame?
	for i = 1, #points - 1 do
		local a, b = points[i], points[i + 1]
		local length = (b - a).Magnitude
		if distance < length then
			return CFrame.lookAt(a:Lerp(b, distance / length), b)
		end
		distance -= length
	end
	return nil
end

function Enemies.spawn(health: number, speed: number, reward: number)
	local part = Instance.new("Part")
	part.Size = Vector3.new(2, 2, 2)
	part.Anchored = true
	part.CanCollide = false
	part.CFrame = CFrame.new(points[1])
	part.Parent = workspace
	local enemy: Enemy = { part = part :: BasePart, health = health, speed = speed, distance = 0, reward = reward }
	table.insert(Enemies.alive, enemy)
end

RunService.Heartbeat:Connect(function(dt)
	for i = #Enemies.alive, 1, -1 do
		local enemy = Enemies.alive[i]
		enemy.distance += enemy.speed * dt
		local cframe = if enemy.health > 0 then placeAt(enemy.distance) else nil
		if cframe then
			enemy.part.CFrame = cframe
		else
			if enemy.health > 0 then -- reached the end: it hurts the base
				Enemies.baseHealth = math.max(0, Enemies.baseHealth - enemy.health)
				workspace:SetAttribute("BaseHealth", Enemies.baseHealth)
			end
			enemy.part:Destroy()
			table.remove(Enemies.alive, i)
		end
	end
end)

return Enemies

• placeAt walks the segments between waypoints and returns the position and facing for a given distance. When the distance passes the last waypoint, the enemy has reached the base and its remaining health is taken from the base.
• Swap the placeholder block for your own enemy model later and move it with PivotTo instead of setting CFrame.
• This moves every enemy on the server, the simplest version to get right. If you plan for very large waves, test with your biggest wave on a real server early and watch performance before adding more.

Towers that target the first enemy in range

Each tower checks ten times a second. If its cooldown is over, it looks at every enemy within its range and picks the one with the largest distance walked. That is the "first" targeting mode, a common default in the genre.

-- Script in ServerScriptService named Towers.
-- Every part tagged Tower shoots the enemy in range that is furthest along the path.
-- Tower stats are attributes: Range, Damage, Cooldown, OwnerId.
local CollectionService = game:GetService("CollectionService")
local Players = game:GetService("Players")
local ServerScriptService = game:GetService("ServerScriptService")
type Enemy = { part: BasePart, health: number, speed: number, distance: number, reward: number }
type EnemiesModule = { alive: { Enemy }, baseHealth: number, spawn: (number, number, number) -> () }
local Enemies = require(ServerScriptService:WaitForChild("Enemies")) :: EnemiesModule

local lastShot: { [Instance]: number } = {}

local function num(tower: Instance, name: string, default: number): number
	local value = tower:GetAttribute(name)
	return if typeof(value) == "number" then value else default
end

local function payOwner(tower: Instance, amount: number)
	local owner = Players:GetPlayerByUserId(num(tower, "OwnerId", 0))
	local leaderstats = owner and owner:FindFirstChild("leaderstats")
	local cash = leaderstats and leaderstats:FindFirstChild("Cash")
	if cash and cash:IsA("IntValue") then
		cash.Value += amount
	end
end

while true do
	task.wait(0.1)
	for _, tower in CollectionService:GetTagged("Tower") do
		if not tower:IsA("BasePart") or os.clock() - (lastShot[tower] or 0) < num(tower, "Cooldown", 1) then
			continue
		end
		local target: Enemy? = nil
		for _, enemy in Enemies.alive do -- "first": the one that walked furthest
			local inRange = (enemy.part.Position - tower.Position).Magnitude <= num(tower, "Range", 20)
			if inRange and enemy.health > 0 and (not target or enemy.distance > target.distance) then
				target = enemy
			end
		end
		if target then
			lastShot[tower] = os.clock()
			target.health -= num(tower, "Damage", 5)
			if target.health <= 0 then
				payOwner(tower, target.reward)
			end
		end
	end
end

• Other targeting modes are one comparison away: "last" picks the smallest distance, "strongest" the most health, "closest" the shortest distance to the tower. Store the mode as another attribute and let players switch it.
• Damage is applied on the server, so a client cannot fake a kill. Add a visual on the clients (a beam or a projectile) by firing a RemoteEvent to all players with the tower and target positions.
• Splash towers damage every enemy within a small radius of the target. Slow towers lower an enemy's speed for a few seconds. Both are a few lines in this loop.

The wave loop

-- Script in ServerScriptService named Waves.
-- Sends each wave, waits until it is cleared, then gives players time to build.
local ServerScriptService = game:GetService("ServerScriptService")
type EnemiesModule = { alive: { any }, baseHealth: number, spawn: (number, number, number) -> () }
local Enemies = require(ServerScriptService:WaitForChild("Enemies")) :: EnemiesModule

local WAVES = { -- count, health, speed (studs per second), cash per kill
	{ count = 8, health = 10, speed = 6, reward = 5 },
	{ count = 12, health = 18, speed = 7, reward = 6 },
	{ count = 6, health = 80, speed = 4, reward = 25 }, -- a slow, tough wave
}

for wave, info in WAVES do
	workspace:SetAttribute("Wave", wave)
	for _ = 1, info.count do
		Enemies.spawn(info.health, info.speed, info.reward)
		task.wait(1)
	end
	repeat
		task.wait(0.5)
	until #Enemies.alive == 0 or Enemies.baseHealth <= 0
	if Enemies.baseHealth <= 0 then
		break
	end
	task.wait(5) -- build time between waves
end

The third wave is slower and much tougher than the second: a different question, not just bigger numbers. Show Wave and BaseHealth from the Workspace attributes in a HUD, and when BaseHealth reaches 0, end the match and send players back to the lobby.

Monetization that fits tower defense

Tower defense players accept paying for towers, convenience and looks. The line is crossed when the strongest strategy in the game can only be bought, especially in co-op, where one player's purchase changes everyone's match.

What brings tower defense players back

• New towers. Each update adds a tower that opens a new strategy, plus an enemy type that rewards using it.
• Difficulty tiers and endless mode. The same map in harder modes is cheap content. Endless mode with a highest-wave leaderboard gives strong players a long-term goal.
• Events. A limited map or enemy set for a few weeks, with a reward that shows you were there.
• Collection. A tower index with locked silhouettes tells players what is left to unlock.
• Daily quests. "Win with a slow tower" or "beat wave 20 on hard" pushes players to try strategies they would skip.

Build it with RoCode

RoCode is an independent AI agent for Roblox Studio, not made by Roblox. You describe the game in a web chat and its Studio plugin writes the Luau and builds parts, scripts and UI in the place you have open. For tower defense it can build the path, the enemy and tower scripts, placement checks and wave tables, and add a HUD, a shop or a round timer from its UI kits. It cannot make tower or enemy meshes or animations, and balancing still needs your playtests.

Build this in Studio ↗

RoCode does not publish the game, create passes or products in Creator Hub, or spend Robux. The free plan gives free credits every day, no card needed. How RoCode builds a game.

Questions

Sources and further reading

• Roblox Creator Docs: Genres. the Tower Defense subgenre under Strategy
• Roblox Creator Docs: Paid random items policy. odds disclosure and ArePaidRandomItemsRestricted
• Roblox Engine API: WorldRoot:GetPartBoundsInBox. box queries use bounding boxes
• Roblox Engine API: CollectionService. tags
• Roblox Creator Docs: Passes. one-time purchases
• Roblox Creator Docs: Subscriptions. battle passes as subscriptions
• RoCode guide: RemoteEvents. checks the server needs on client requests

How the code was checked: every script on this page passes Luau's strict type checker against Roblox's API definitions (luau-lsp, 26 October 2026). A type check catches misspelt APIs and wrong types, not game logic, so playtest in Studio before you publish.