Emulating the VMU.
The buttons A and B are mapped to those in the VMU. Arrow keys are too. M and S are mapped to MODE and SELECT.
The Visual Memory Unit (VMU), also referred to as the Visual Memory System (ビジュアルメモリ, Bijuaru Memori) (VMS) in Japan and Europe, is the primary memory card produced by Sega for the Dreamcast home video game console. The device features a monochrome liquid crystal display (LCD), multiplayer gaming capability (via connectors at the top), second screen functionality, a real-time clock, file manager, built-in flash memory, and sound capability.