I have a forced vertical scrolling on my game. When the scrolling catches up my player, it kills him. Now, I made a lava ground. This lava ground has the same scrolling speed as my forced scrolling. So when the lava ground catches my player, it kills him. It's perfect except that. I tried to set a linear velocity to it, but the problem is when the scrolling accelerates, my wall preserves his speed. So, after a moment the scrolling is too fast and my lava ground leaves the screen. Is there a trick to attach my obstacle to the camera scrolling or to synchronize their two speed? Could you help me?