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A Bot That Chases

Lesson 14 of 20 in Coddy's Roblox Game: Battlegrounds course.

Now an opponent. A bot is a model in ServerStorage.Bot with a Humanoid, cloned onto the red pad. Its mind is a loop in its own thread: every quarter second, find the nearest living player it can see (within Settings.BotSight) and walk at them with Humanoid:MoveTo.

while bot.Parent and humanoid.Health > 0 do
	local target = nearestCharacter(root.Position)
	if target then
		humanoid:MoveTo(target.HumanoidRootPart.Position)
	end
	task.wait(0.25)
end

Finding the nearest is the classic loop: start with nothing and the sight range as the best distance, and keep anyone closer.

Roblox lets a nearby player's client run an unanchored model's physics, and a server call such as ApplyImpulse on it then does nothing. Your slam knocks bots back from the server, so keep each bot's physics there: bot.HumanoidRootPart:SetNetworkOwner(nil), once the bot is in the workspace.

challenge icon

Challenge

Hard
  1. Add local bots = workspace.Bots.
  2. Write nearestCharacter(position): the character of the nearest living player within Settings.BotSight, and its distance (or nil).
  3. Write runBot(bot): while the bot is alive, walk at the nearest character, or stand still, and wait 0.25 seconds.
  4. Write spawnBot(): clone the Bot 3 studs above workspace.BotSpawn, set its MaxHealth, Health and WalkSpeed from Settings, parent it to bots, keep its physics on the server, make its health bar follow its health, and start runBot. Spawn one.

Press Play and walk toward the red pad. Then Check.

Try it yourself

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

local remotes = game.ReplicatedStorage.Remotes
local lastSwing = {} -- player -> when they last swung
local combo = {} -- player -> { hits in a row, when the last one landed }

-- Roblox's own sword animations
local slash = Instance.new("Animation")
slash.AnimationId = "rbxassetid://522635514"
local lunge = Instance.new("Animation")
lunge.AnimationId = "rbxassetid://522638767"

print("Swords deal " .. Settings.SwordDamage .. " damage")

-- A number that floats over whoever was hit, for a moment
local function damageNumber(character, amount)
	local root = character:FindFirstChild("HumanoidRootPart")
	if not root then
		return
	end
	local tag = Instance.new("BillboardGui")
	tag.Name = "Damage"
	tag.Size = UDim2.fromOffset(60, 30)
	tag.StudsOffset = Vector3.new(0, 4.5, 0)
	tag.Adornee = root
	local text = Instance.new("TextLabel")
	text.Size = UDim2.fromScale(1, 1)
	text.BackgroundTransparency = 1
	text.TextColor3 = Color3.fromRGB(255, 220, 80)
	text.TextScaled = true
	text.Text = "-" .. math.round(amount)
	text.Parent = tag
	tag.Parent = character
	Debris:AddItem(tag, 0.8)
end

-- Every hit in the game goes through here
local function hurt(humanoid, amount)
	if humanoid.Health <= 0 then
		return
	end
	local character = humanoid.Parent
	-- a block takes most of the hit
	if character:GetAttribute("Blocking") then
		amount *= Settings.BlockMultiplier
	end
	humanoid:TakeDamage(amount)
	damageNumber(character, amount)
end

-- A stun freezes someone for a moment
local function stun(humanoid)
	local character = humanoid.Parent
	if character:GetAttribute("Stunned") then
		return
	end
	character:SetAttribute("Stunned", true)
	local speed = humanoid.WalkSpeed
	humanoid.WalkSpeed = 0
	task.delay(Settings.StunTime, function()
		if character.Parent then
			humanoid.WalkSpeed = speed
			character:SetAttribute("Stunned", nil)
		end
	end)
end

-- A swing: the animation, then everyone in the box in front of you is hit
local function swing(player)
	local character = player.Character
	local root = character and character:FindFirstChild("HumanoidRootPart")
	if not root or character.Humanoid.Health <= 0 then
		return
	end
	local now = time()
	if lastSwing[player] and now - lastSwing[player] < Settings.SwingCooldown then
		return
	end
	lastSwing[player] = now
	-- three swings in a row make a combo; the third is a lunge
	local c = combo[player]
	if c and now - c.last <= Settings.ComboWindow then
		c.count = c.count % 3 + 1
	else
		c = { count = 1 }
		combo[player] = c
	end
	c.last = now
	local finisher = c.count == 3
	character.Humanoid.Animator:LoadAnimation(finisher and lunge or slash):Play()
	-- the box in front of you, never your own body
	local params = OverlapParams.new()
	params.FilterDescendantsInstances = { character }
	local box = root.CFrame * CFrame.new(0, 0, -3)
	local hit = {} -- each humanoid once per swing
	for _, part in workspace:GetPartBoundsInBox(box, Settings.HitboxSize, params) do
		local humanoid = part.Parent:FindFirstChildOfClass("Humanoid")
		if humanoid and not hit[humanoid] then
			hit[humanoid] = true
			hurt(humanoid, Settings.ComboDamage[c.count])
			if finisher then
				stun(humanoid)
			end
		end
	end
end

-- The abilities, by name: what each one does
local abilities = {}

function abilities.Dash(player, character, root)
	root.AssemblyLinearVelocity = root.CFrame.LookVector * Settings.DashSpeed + Vector3.new(0, 15, 0)
end

-- everyone around you is hit and thrown away from you
function abilities.Slam(player, character, root)
	local params = OverlapParams.new()
	params.FilterDescendantsInstances = { character }
	local hit = {}
	for _, part in workspace:GetPartBoundsInRadius(root.Position, Settings.SlamRadius, params) do
		local humanoid = part.Parent:FindFirstChildOfClass("Humanoid")
		local theirRoot = part.Parent:FindFirstChild("HumanoidRootPart")
		if humanoid and theirRoot and not hit[humanoid] then
			hit[humanoid] = true
			hurt(humanoid, Settings.SlamDamage)
			local away = (theirRoot.Position - root.Position) * Vector3.new(1, 0, 1)
			if away.Magnitude > 0 then
				away = away.Unit
			end
			theirRoot:ApplyImpulse((away * Settings.SlamKnockback + Vector3.new(0, 40, 0)) * theirRoot.AssemblyMass)
		end
	end
end

function abilities.Block(player, character)
	character:SetAttribute("Blocking", true)
	task.delay(Settings.BlockTime, function()
		if character.Parent then
			character:SetAttribute("Blocking", nil)
		end
	end)
end

-- The client asks for an ability by name. The server checks it: a real
-- ability, a living player, and its cooldown over. When it is ready again
-- is an attribute of the player, so their screen can show it.
remotes.Ability.OnServerEvent:Connect(function(player, name)
	if typeof(name) ~= "string" or not abilities[name] then
		return
	end
	local character = player.Character
	local root = character and character:FindFirstChild("HumanoidRootPart")
	if not root or character.Humanoid.Health <= 0 then
		return
	end
	local now = workspace:GetServerTimeNow()
	if now < (player:GetAttribute(name .. "ReadyAt") or 0) then
		return
	end
	player:SetAttribute(name .. "ReadyAt", now + Settings.Cooldowns[name])
	abilities[name](player, character, root)
end)

-- Every player gets Kills on the leaderboard, and a sword every life
Players.PlayerAdded:Connect(function(player)
	local leaderstats = Instance.new("Folder")
	leaderstats.Name = "leaderstats"
	leaderstats.Parent = player

	local kills = Instance.new("IntValue")
	kills.Name = "Kills"
	kills.Parent = leaderstats

	player.CharacterAdded:Connect(function()
		local sword = ServerStorage.Sword:Clone()
		sword.Parent = player.Backpack
		sword.Activated:Connect(function()
			swing(player)
		end)
	end)
end)

-- The training dummy: its health bar follows its health, and a beaten
-- dummy comes back after a moment, a fresh copy in the same place
local function setupDummy(dummy)
	local humanoid = dummy.Humanoid
	humanoid.HealthChanged:Connect(function(health)
		dummy.HealthBar.Back.Fill.Size = UDim2.fromScale(health / humanoid.MaxHealth, 1)
	end)
	humanoid.Died:Connect(function()
		local spot = dummy:GetPivot()
		task.wait(0.5)
		dummy:Destroy()
		task.wait(Settings.DummyRespawn)
		local fresh = ServerStorage.Dummy:Clone()
		fresh:PivotTo(spot)
		fresh.Parent = workspace
		setupDummy(fresh)
	end)
end
setupDummy(workspace.Dummy)
quiz iconTest yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Roblox Game: Battlegrounds