Designed as a version of Boulder Dash that could fit onto a floppy disk, the designers had a hard time for this approach in order to create better graphics. (The original Amiga Supaplex version had to fit on a standard 880kB floppy disk and it needed to run on a standard 512kB Amiga like the original A500 or A2000. In fact: The Amiga version could not be copied onto the hardrive due to copy protection and its custom disk format.)
The game comes with 111 levels though many unofficial level sets have been released that greatly increase that number. The game was released for Amiga and MS-DOS. (Two guys from the London region started to program a full version for the Atari ST, but it was never released, because of the limited graphical support.)
Due to hardware dependent programming, the PC version of Supaplex ran twice as fast as PCs became faster. Herman Perk disassembled the game, debugged it and re-assembled it again. The result became known as SpeedFix. Extra features have also been added without changing the game itself.
The developers of the game have declared the software freeware.
Source: Wikipedia, "Supaplex," available under the CC-BY-SA License.