"create me a simple hotel keycard system where players click a button and it gives them a key unique to the player, and to a room! Make sure to include good instructions for the implementation of such system."

To create a simple hotel keycard system, follow the steps below:

1. Create a button in a GUI that players can click to get a keycard.
2. Create a server script that listens for the button click and assigns a unique keycard to the player.
3. Create a door script that checks if the player has the correct keycard before allowing them to enter the room.

Here's a detailed implementation:

Step 1: Create a button in a GUI

1. In the Roblox Studio, insert a ScreenGui into StarterGui.
2. Inside the ScreenGui, insert a TextButton and customize it as you like.

Step 2: Create a server script for assigning keycards

1. Insert a Script into ServerScriptService and name it "KeycardSystem".
2. Use the following code for the script:

```lua
local function onButtonClicked(player)
    local keycard = Instance.new("StringValue")
    keycard.Name = "Keycard"
    keycard.Value = "Room" .. math.random(1, 10) -- Assuming there are 10 rooms
    keycard.Parent = player
end

game.ReplicatedStorage.RemoteEvent.OnServerEvent:Connect(onButtonClicked)
```

Step 3: Create a door script to check for keycards

1. Create a part that acts as the door in your hotel room.
2. Insert a Script into the door part and use the following code:

```lua
local door = script.Parent

local function onTouched(hit)
    local player = game.Players:GetPlayerFromCharacter(hit.Parent)
    if player then
        local keycard = player:FindFirstChild("Keycard")
        if keycard and keycard.Value == "Room1" then -- Change "Room1" to the room number the door belongs to
            door.Transparency = 0.5
            door.CanCollide = false
            wait(3)
            door.Transparency = 0
            door.CanCollide = true
        end
    end
end

door.Touched:Connect(onTouched)
```

Step 4: Connect the GUI button to the server script

1. Insert a LocalScript into the TextButton created in Step 1.
2. Use the following code for the LocalScript:

```lua
local button = script.Parent
local remoteEvent = game.ReplicatedStorage.RemoteEvent

local function onClick()
    remoteEvent:FireServer(game.Players.LocalPlayer)
end

button.MouseButton1Click:Connect(onClick)
```

That's it! Now you have a simple hotel keycard system. Players can click the button to get a keycard, and the door will only open if they have the correct keycard.