Instructions:

Use your Arrow keys to move the ball. The ball will continue in its path until it is stopped by a wall. If the ball hits a portal: it will appear out of the matching portal traveling in the same direction when it entered the first portal.
A yellow arrow on the map is called a funnel: Funnels act as on way streets. If the ball hits the funnel traveling the way of the arrow, it passes through, otherwise it acts as a wall.