Oh no! Mario is now available for the Atari ST. Phew, thankfully, I'm lying!! This is actually a cool intro screen that was created to be a main-menu for some demo that never got completed. Good old Demozoo informs that it's by Channel 38 and features neat music and a large "play area" making good use of those borders. Oh yeah, so nice!!
My apologies for this video recording which is pretty poor. A real ST/e performs silky smooth.