function init(self)
    msg.post(".", "acquire_input_focus")
    go.animate(".", "position.x", go.PLAYBACK_LOOP_PINGPONG, 2000, go.EASING_INOUTQUAD, 10) -- <1>
    msg.post("camera", "follow") -- <2>
    self.follow = true -- <3>
end


function on_input(self, action_id, action)
    if action_id == hash("touch") and action.pressed then -- <4>
        self.follow = not self.follow
        if self.follow then
            msg.post("camera", "follow")
        else
            msg.post("camera", "unfollow")
        end
    end
end

--[[
1. Move this game object back and forth across the scene.
2. Send a message to the camera game object telling it to follow this game object.
3. Keep track of if the camera is following this game object or not.
4. Toggle between following and not following the game object when the left mouse button is clicked or the screen is touched.
--]]

function on_message(self, message_id, message, sender)
    if message_id == hash("follow") then -- <1>
        go.set_parent(".", sender) -- <2>
    elseif message_id == hash("unfollow") then -- <3>
        go.set_parent("camera", nil, true)
    end
end

--[[
1. Start following the game object that sent the `follow` message.
2. This is done by parenting the camera component to the game object that sent the message.
3. Stop following any game object. This is done removing the parent game object while maintaining the current world transform.
--]]