Flux

Flux is a music visualizer software. When the Mega Drive is connected to a Sega Mega-CD, an audio CD is in the CD tray, and this cartridge in the Mega Drive, Flux will have the Mega CD play the music on the CD and show various user-configurable effects (the default being a two-channel oscilloscope). B pauses playback, Left and Right skip tracks, and Start brings up the configuration panel.