Documentation › Tutorials › Games › Marble Game

Player Movement

The next step is to add controls so the player can move the ball by pressing keys on their keyboard. We will use the Window:KeyDown() function to check if a key is pressed, and if it is we will apply a force to the ball. Enter this code into your custom script:
function Script:Start()
    --Create a camera
    self.camera = Camera:Create()
    --Update the camera
    self:UpdateCamera()
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()
    --If the 'W' key is pressed add a force to the entity
    if window:KeyDown(Key.W) then
        self.entity:AddForce(0,0,10,true)
    end
end
function Script:UpdateWorld()
    --Update the camera each frame
    self:UpdateCamera()
end

Run the game, and you will be able to control the ball by pressing the W key. In fact, you can send it right over the edge into space!

Of course, we want to be able to move our ball in all directions, so let's add some more code to handle that: The code below will allow the ball to roll in all directions using the WASD keys for up, left, back, and right movement:

function Script:Start()
    --Create a camera
    self.camera = Camera:Create()
    --Update the camera
    self:UpdateCamera()
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

Viola! You now have your very own moving ball.