Loops Practice - Creating a Timed Bridge

This project is another example of using for loops in a practical way. For this bridge, players will touch a button to make a bridge walkable for a limited time before it disappears. To create a timer and show the remaining time to a player, you'll use for loops.

Setting up the Project

This bridge can be included in any game project with movement-based challenges, like an obby.

Creating Parts

  1. Find a place to build a bridge, like a river or a large gap in an obby. Create three anchored parts like below.

    • TimerDisplay
    • Bridge
    • ButtonBridge

  2. When inactive, the bridge will be semi-transparent. To do so, select the Bridge and change it's properties.

    • Transparency = 0.8
    • CanCollide = False

Creating the Timer Display

When crossing the bridge, players will need to see how many seconds are left before the bridge disappears. One way to display images or text is by adding an object called a Surface GUI to a part. Surface GUIs can also be used to create in-game signs, custom health bars, and inventory systems. This tutorial will go through this quickly, but more information can be found in the Tutorials section.

  1. Select TimerDisplay and add a SurfaceGui. Then, parented to the Surface Gui, add a TextLabel.

  2. Select the Surface GUI. In the Properties, make the following changes:

    • Change the Face so you can see the text label on the front of the timer where the player is looking.

  3. Select the TextLabel. In the Properties, make the following changes:

    • Set Size to {1, 0},{1, 0}.
    • Set TextScaled to true.
    • Set Text to be blank. Text will be updated using the script.

Setting up the Script

Now that the timer is in place, create a script to control the bridge and display the countdown number to players.

  1. In the Bridge part, add a new script named TimedBridge. In that script, create the following variables.

    local bridge = script.Parent

    local button = workspace.ButtonBridge

    local timerText = workspace.TimerDisplay.SurfaceGui.TextLabel

    

    -- How long the bridge will stay solid

    local timerDuration = 5

Coding the Touch Interaction

To use the bridge, you'll need to create two functions. One function will make the bridge walkable and display the timer. The other function will listen for if a player touches the button that activates the bridge.

  1. Create a new function named startTimer() with a print statement inside. You'll use the print statement to test your code.

    local timerDuration = 5

    

    local function startTimer()

        print("Countdown started")

    end

  2. Code a function named buttonPressed() to check if a humanoid touches the button. The function should accept a parameter of partTouched, and then have an empty if statement if a humanoid is detected in that part.

    local function startTimer()

       print("Countdown started")

    end

    

    local function buttonPressed(partTouched)

       local character = partTouched.Parent

       local humanoid = character:FindFirstChildWhichIsA("Humanoid")

    

       if humanoid then

    

       end

    end

  3. To start the timer, in the if statement, call the startTimer() function.

    local function buttonPressed(otherPart)

       local character = otherPart.Parent

       local humanoid = character:FindFirstChildWhichIsA("Humanoid")

       if humanoid then

          startTimer()

       end

    end

  4. Under the end of buttonPressed(), connect the buttonPressed() function to the button's Touched event.

    local function buttonPressed(otherPart)

       local character = otherPart.Parent

       local humanoid = character:FindFirstChildWhichIsA("Humanoid")

       if humanoid then

          startTimer()

       end

    

    end

    

    button.Touched:Connect(buttonPressed)

  5. Run the project. Touch the part and check in the Output window to see the print statement.

Troubleshooting Tips

At this point, if the bridge doesn't work as intended, try one of the following below.

Issue: Error message saying: "... is not a valid member of workspace".

  • In the TimedBridge script, check that all parts are spelled exactly as they're seen in the Explorer.

Issue: Can't see the parts.

  • Make sure all three parts are Anchored.
  • Check the Transparency property for the bridge.

Creating the Timer

Whenever players step on the bridge, startTimer() will make the bridge walkable and start the timer. Once the timer reaches 0, the bridge will become unwalkable, causing anyone who's not fast enough to fall.

Making the Bridge Walkable

To start, the script will need to make the bridge solid, or collidable and then start a timer until it becomes unwalkable.

  1. To make the bridge walkable, in startTimer(), change the bridge's Transparency property to 0 (opaque) and the CanCollide property to true.

    local function startTimer()

       -- Make the bridge visible and walkable

       bridge.Transparency = 0

       bridge.CanCollide = true

    end

  2. To create a timer that counts down, create a for loop with the following values.

    • Control Variable: named count, set to timerDuration.
    • End: 0
    • Increment: -1
    local function startTimer()

       -- Make the bridge visible and walkable

       bridge.Transparency = 0

       bridge.CanCollide = true

    

       for count = timerDuration, 0, -1 do

    

       end

    

    end

  3. To show the timer to players, change the text in timerText to display count by typing timerText.Text = count. Each time the for loop goes through an iteration, it'll show players the next number in the timer.

    for count = timerDuration, 0, -1 do

       timerText.Text = count

    end

  4. Use a task.wait function to make the for loop run only once a second.

    for count = timerDuration, 0, -1 do

       timerText.Text = count

       task.wait(1)

    end

  5. Run the game. When you touch the button, the bridge should appear and the timer will start, then complete.

Keeping the Bridge from Restarting

Notice though, if you move around on the button, the timer will keep restarting.

This is because the for loop is being called each time you touch the button and starting the for loop from the beginning. To keep the timer from constantly restarting, you'll need to add a boolean, a type of variable, that will control whether or not startTimer() is allowed to be called again.

Booleans are written the same way as other variables, but instead of using numbers or strings, they can only be set to true or false. In this situation, the script will use a boolean to check if the timer is currently running before starting it.

  1. At the top of your script, under your variables, create a variable named timerActive and set it to false since nobody has pressed the button yet.

    local timerDuration = 5

    local timerActive = false

    

    local function startTimer()

  2. To makes sure the timer only starts when the timerActive boolean is false, add a second condition to the if statement in buttonPressed().

    local function buttonPressed(otherPart)

       local character = otherPart.Parent

       local humanoid = character:FindFirstChildWhichIsA("Humanoid")

       if humanoid and timerActive == false then

          startTimer()

       end

    

    end

  3. To keep startTimer() from running again before the timer runs out, set the boolean timerActive to true.

    local function startTimer()

       timerActive = true

       bridge.Transparency = 0

       bridge.CanCollide = true

  4. In the startTimer() function, after the for loop, set the bridge back to its original properties by changing the bridge's transparency to 0.8 and CanCollide to false.

    local function startTimer()

       timerActive = true

       bridge.Transparency = 0

       bridge.CanCollide = true

    

       -- For loop that counts down from timerDuration

       for count = timerDuration, 0, -1 do

          timerText.Text = count

          task.wait(1)

       end

    

       -- Make the bridge not walkable

       bridge.Transparency = 0.8

       bridge.CanCollide = false

    end

  5. One last thing to reset the bridge is to change the timerText to an empty string like how it was originally. Then, set the timerActive boolean to false.

    bridge.Transparency = 0.8

    bridge.CanCollide = false

    timerText.Text = ""

    timerActive = false

  6. Playtest and check to make sure the bridge can be used multiple times.

Complete Timed Bridge Script

local bridge = script.Parent

-- Gets the button as it's typed in the Explorer

local button = workspace.ButtonBridge



-- Gets the part for the display

local timerPart = workspace.TimerDisplay

-- Gets the Text that will display the timer

local timerText = timerPart.SurfaceGui.TextLabel



-- How long players have to cross the bridge

local timerDuration = 5

local timerActive = false



local function startTimer()

    print("Countdown started")

	timerActive = true

	bridge.Transparency = 0

	bridge.CanCollide = true



	-- For loop that counts down from timerDuration

	for count = timerDuration, 0, -1 do

		timerText.Text = count

		task.wait(1)

	end



	-- Make the bridge not walkable

	bridge.Transparency = 0.8

	bridge.CanCollide = false

	timerText.Text = ""

	timerActive = false



end



local function buttonPressed (partTouched)

	local character = partTouched.Parent

	local humanoid = character:FindFirstChildWhichIsA("Humanoid")

	print("part touched")



	if humanoid and timerActive == false then

		print("starting timer")

		startTimer()

	end

end



button.Touched:Connect(buttonPressed)

Summary

Loops can be combined with different means of interaction to create fun gameplay moments. In this tutorial, a timed bridge is created using a for loop that functions as a countdown. During the countdown, players are given a limited time to get across.

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