Spelunx and the Caves of Mr. Seudo is an educational computer game intended for young children developed by Cyan (now Cyan Worlds) in 1991. It was designed by the brothers Robyn and Rand Miller (better known now as the creators of Myst). The game was programmed and implemented using HyperCard, with Robyn Miller hand-drawing all of the in-game graphics and scenery. The game's title was derived from the verb "to spelunk", referring to the act of exploring caves.