Create a large box brush underneath your level. Make sure it is big enough the player will always hit it if they fall into space:

With this box still selected, select the Scene tab in the side panel. Select the General tab in the properties editor and set the name of this object to "Kill Trigger". Select the Script tab in the properties editor and press button with a folder icon to open a file open dialog. Select the file "Scripts\Objects\Triggers\TriggerPain.lua". We want this trigger to kill the player immediately, so set the damage value to 100.

If we open the TriggerPain script, we can see how it works. In the Script:Collision() function, this script will check to see if the colliding entity has a script with a TakeDamage() function declared. If the function is present, this script will call it, passing its own damage value in as a function argument. However, our player script does not have a TakeDamage() function, so without further modification this trigger will have no effect.

function Script:Collision(entity, position, normal, speed)
    if self.enabled then
        if entity.script then
            if type(entity.script.TakeDamage)=="function" then
                entity.script:TakeDamage(self.damage)
            end
        end
    end
end

Let's open our "MyBallPlayer.lua" script again and make some modifications. First, we want the player to start with 100 health. We also want to get the player's starting position so that we can use it later to reposition them if they die. Add these two lines of code inside the Script:Start() function:

self.health = 100
self.startposition = self.entity:GetPosition()

Now we will add a TakeDamage() function so the pain trigger has something to call. Add this function at the end of the "MyBallPlayer.lua" script:

function Script:TakeDamage(damage)
    self.health = self.health - 100
    if self.health<=0 then
        self.health=100
        self.entity:SetPosition(self.startposition)
        self.entity:SetRotation(0,0,0)
        self.entity:SetVelocity(Vec3(0,0,0))
        self.entity:SetOmega(Vec3(0,0,0))
    end
end

Our new Script:TakeDamage() function will subtract health from the player when it is called. If the player's health is less than or equal to zero, then the player will respawn at their original starting position with 100 health. We also set their rotation, velocity, and omega (rotational velocity) back to zero so they can start the level over and try again. Go ahead and run the game now. You should be able to roll the ball off into space and respawn at the start of the map.

Here is the finished "MyBallPlayer.lua" script. It looks like a lot of code, but because we went through it all bit by bit, you now have a good understand of how it works and what it does:

function Script:Start()
    --Create a camera
    self.camera = Camera:Create()
    --Update the camera
    self:UpdateCamera()
    --Load a custom font
    self.font = Font:Load("Fonts/Ranchers-Regular.ttf",18)
    self.health = 100
    self.startposition = self.entity:GetPosition()
end
--This function will be called by the pain trigger
function Script:TakeDamage(damage)
    self.health = self.health - 100
    if self.health<=0 then
        self.health=100
        self.entity:SetPosition(self.startposition)
        self.entity:SetRotation(0,0,0)
        self.entity:SetVelocity(Vec3(0,0,0))
        self.entity:SetOmega(Vec3(0,0,0))
    end
end
--Adjust the camera orientation relative to the ball
function Script:UpdateCamera()
    self.camera:SetRotation(45,0,0)
    self.camera:SetPosition(self.entity:GetPosition())
    self.camera:Move(0,0,-4)
end
function Script:UpdatePhysics()
    --Get the game window
    local window = Window:GetCurrent()
    
    --Add force to the player when a key is pressed
    if window:KeyDown(Key.W) then self.entity:AddForce(0,0,10,true) end
    if window:KeyDown(Key.A) then self.entity:AddForce(-10,0,0,true) end
    if window:KeyDown(Key.D) then self.entity:AddForce(10,0,0,true) end
    if window:KeyDown(Key.S) then self.entity:AddForce(0,0,-10,true) end
end
function Script:UpdateWorld()
    --Update the camera each frame
    self:UpdateCamera()
end
function Script:PostRender(context)
    --Set the font to a cartoonish style
    if self.font~=nil then
        context:SetFont(self.font)
    end
    
    if TotalCoins~=nil and CoinsCollected~=nil then
        --Enable alpha blending
        context:SetBlendMode(Blend.Alpha)
        
        --Set drawing color to red
        context:SetColor(1,0,0,1)
        
        --Combine our variables into some text
        local text = "Coins: "..CoinsCollected.." / "..TotalCoins
        
        --Draw the text in the upper right corner of the screen
        context:DrawText(text,context:GetWidth()-context:GetFont():GetTextWidth(text)-4,4)
    
    end
    --Restore the default font for drawing
    context:SetFont(nil)
end