The DataModel

The DataModel is unchanged. game is the root, services hang off it, and Instance behaves exactly as it does on Roblox — same properties, same events, same parenting rules, same replication model.

Services#

Every service you would reach for is present:

local Players = game:GetService("Players")
local RunService = game:GetService("RunService")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local CollectionService = game:GetService("CollectionService")
local TweenService = game:GetService("TweenService")
local UserInputService = game:GetService("UserInputService")

Services fall into three groups:

Check before you call:

if Engine.Capabilities.Monetisation then
	local MarketplaceService = game:GetService("MarketplaceService")
	-- …
end

Engine.Capabilities is a plain table of booleans resolved at build time, so the analyser can flag unguarded platform calls statically.

Instances#

Instance.new, :Clone(), :Destroy(), :FindFirstChild(), :WaitForChild(), :GetDescendants(), :IsA() — all present, all with the same semantics.

local part = Instance.new("Part")
part.Size = Vector3.new(4, 1, 4)
part.Position = Vector3.new(0, 10, 0)
part.Anchored = true
part.BrickColor = BrickColor.new("Really blue")
part.Parent = workspace

Attributes and tags work the same way and are the recommended place for gameplay metadata, because they survive round trips through both editors:

part:SetAttribute("Damage", 25)
CollectionService:AddTag(part, "Hazard")

for _, hazard in CollectionService:GetTagged("Hazard") do
	print(hazard:GetAttribute("Damage"))
end

Replication#

The client/server split is preserved. RunService:IsServer() and :IsClient() behave as expected, RemoteEvent and RemoteFunction work identically, and the same replication filtering applies to ReplicatedStorage versus ServerStorage.

-- server
local remote = Instance.new("RemoteEvent")
remote.Name = "Damaged"
remote.Parent = ReplicatedStorage
remote:FireClient(player, 25)

-- client
ReplicatedStorage:WaitForChild("Damaged").OnClientEvent:Connect(function(amount)
	print("took", amount)
end)

In a single-player standalone build the server and client run in the same process, but the boundary is still enforced — code that would fail to replicate on Roblox fails locally too, so you cannot accidentally write a game that only works offline.

Additions#

Standalone targets add instances that have no Roblox counterpart. They are inert on the roblox target, so leaving them in your place is safe.

local config = Instance.new("EngineConfiguration")
config.WindowTitle = "My Game"
config.DefaultResolution = Vector2.new(1600, 900)
config.TickRate = 60
config.Parent = game

The Engine global#

Available on every target; on Roblox it reports Engine.Platform == Enum.Platform.Roblox and exposes only the members that make sense there.

Full signatures are in API differences.