Supaplex is a remake of the original Boulder Dash/Pac-Man crossbreed, which was released for MS-DOS in the early 90s. That original has since been published as freeware, spawning multiple reincarnations and copies, of which this app is one. It contains the same set of levels as the original, with an updated soundtrack and higher-resolution graphics.
Gameplay consists of moving around an orange munchy-head called Murphy, collecting colorful "infotrons" and avoiding falling "zonks", among other obstacles, before reaching the exit for the next level. Objects in the scene are organized in a grid which is affected by gravity once Murphy chomps through the surrounding base tiles. Each level is quite extensive, and to this end the interface of this particular remake is helpful, because it allows you to click and drag on the screen to view the entirety of the level. Unfortunately it's still pretty difficult, because a level restart is required every time you or all your exits are destroyed; there are no checkpoints.
While I can see the nostalgic appeal for a subset of players, the game is a bit intense for the uninitiated. Even those who enjoy the gameplay might prefer to use the original freeware version with DOSBox, or try one of the other free implementations.
Sam's Protip: The developer has published two other versions with 111 new levels apiece for the same price tag. Sure, you could buy those... or you could download the thousands of free levels for the original.