 In the one month interim between Sonics US debut and his Japanese  release, a few minor graphical enhancements were worked in. In the  US/European version, the clouds at the title screen and in Green  Hill are still, but in the Japanese version, they scroll (rather  speedily) from right to left. Ripple effects were added to the  underwater segments of the Labyrinth Zone, and the stage order at  the level select menu was corrected.