Slope Tunnel is a well-known slope game, except that the ball now moves through a tunnel that is closed on all sides rather than down a track.
In Slope Tunnel, just like in the other games in the series, your goal is to move the game projectile to the right or left to avoid perilous obstacles. In this instance, these barriers are like fissures in the tunnel's wall; if you fall through them, you'll lose and have to start over.
The slightly vertical nearby walls are instantaneously turned horizontal as the ball rolls over them, "crushing" under itself. The tunnel is made by the way the ball moves, but you can only see a small part of it. It often cracks, sometimes right in front of the ball.