function screen_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 num_is_pos(number)
	if number > 0 then
		return true
	else return false
	end
end

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

	--If ball hits screen wall
	if ball.x >= screen.width or ball.x < 0 then
		ball.x_speed = ball.x_speed * -1
	end

	--If ball hits screen top/bottom
	if ball.y >= screen.height or ball.y <0 then
		ball.y_speed = ball.y_speed * -1
	end

	--If ball hits paddle 
	if ball.y + 1 >= player.y and
		 ball.x >= player.x and
		 ball.x <= player.x + player.width then
		 ball.y_speed = ball.y_speed *-1
		 paddle_hit = true
	 end

	 if paddle_hit == true then
		 if ball.x < player.x + (player.width/2) and
			 num_is_pos(ball.x_speed) then
			 ball.x_speed = ball.x_speed *-1
		 elseif ball.x > player.x + (player.width/2) and
			 not num_is_pos(ball.x_speed) then
			 ball.x_speed = ball.x_speed *-1
		 end
	 end

	return ball
end