A Bot That Chases

Lesson 17 of 25 in Coddy's Roblox Game: Battlegrounds course.

The bot needs a mind: a loop in its own thread that, every quarter second, finds the nearest living player it can see (within Settings.BotSight) and walks 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. task.spawn(runBot, bot) starts the loop without stopping the rest of the script.

Challenge

Hard

Make the bot walk at you.

Write nearestCharacter(position): the nearest living player's character within Settings.BotSight, and its distance.
Write runBot(bot): while the bot is alive, MoveTo the nearest character's root (or its own position), then task.wait(0.25).
At the end of spawnBot: task.spawn(runBot, bot).

Press Play and walk toward the red pad: the bot comes for you. 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 bots = workspace.Bots
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)
	print(character.Name .. " is stunned")
	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 = {}

-- a player's own device moves their character, so the dash happens there
function abilities.Dash(player)
	remotes.Ability:FireClient(player, "Dash")
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 a sword every life
Players.PlayerAdded:Connect(function(player)
	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)

-- Lesson 17: A Bot That Chases goes here

-- A new bot on the red pad, with its numbers and a health bar
local function spawnBot()
	local bot = ServerStorage.Bot:Clone()
	bot:PivotTo(workspace.BotSpawn.CFrame + Vector3.new(0, 3, 0))
	bot.Humanoid.MaxHealth = Settings.BotHealth
	bot.Humanoid.Health = Settings.BotHealth
	bot.Humanoid.WalkSpeed = Settings.BotSpeed
	bot.Parent = bots
	-- keep the bot's physics on the server, so the slam's knockback moves it
	bot.HumanoidRootPart:SetNetworkOwner(nil)
	bot.Humanoid.HealthChanged:Connect(function(health)
		bot.HealthBar.Back.Fill.Size = UDim2.fromScale(health / bot.Humanoid.MaxHealth, 1)
	end)
end

spawnBot()