RnD is a fantastic multiple-clone of tile-based games, like Boulder Dash, Emerald Mine, Supaplex and Sokoban. The program includes a set of levels for each of them, along with a couple of tutorials.
The player is usually called "Rockford". In RnD, Rockford is a fellow with a suit and a cap of matching color, that can be either yellow, red, green or blue. In Supaplex, the player is a smiling orange ball called "Murphy". All these games involve going around in a two-dimensional map. There can be lot of things to do inside that map:
Finally - as the most important thing :
you will find the exit door and you will pass it, solving the level.