function col_detect(object, display)
  if not (object.x >= -1 and 
    object.x <= (display.width - object.width)) then
    return false
  end 

  if not (object.y >= -1 and 
     object.y <= (display.height - object.height)) then
     return false
  end 

  return true
end

function create_object(start_x, start_y, width, height, speed)
  local	object = {}
	object.x = start_x
	object.y = start_y
	object.width = width
	object.height = height
	object.speed = speed
	return object
end

function ball_bounce(ball)
	ball.x = ball.x + ball.x_speed
	ball.y = ball.y + ball.y_speed

	if ball.x >= screen.width or ball.x < 0 then
		ball.x_speed = ball.x_speed * -1
	end
	if ball.y >= screen.height or ball.y <0 then
		ball.y_speed = ball.y_speed * -1
	end
	return ball
end