The first notable version was that for the Sharp MZ-800 computer, created by the Czechoslovak programmer Antonín Spurný from Roudnice nad Labem, a town 50 kilometers north of Prague. He was in his late twenties and worked as a chief electrician at a metal container factory while spending much of his leisure time as a computer hobbyist. He owned a Sharp MZ-800, a Japanese computer that had been imported into Czechoslovakia since 1986 to satiate the demand for home computers. The problem with the MZ-800 was that with next to no commercial software was ever produced for it. Most games available for this machine were legacy titles from the previous 8-bit Sharp models and unofficial ports from the Sinclair ZX Spectrum.
While generally incompatible with the ZX Spectrum, the Sharp MZ-800 had the same CPU, allowing Spurný to reuse most of the Spectrum Boulder Dash code for the Sharp version, save for the parts that handled controls, display, and sound. Spurný disassembled the code, identified key points where the program communicated with input and output of the machine, and rewrote them. He did not stop at building a working MZ-800 version but attempted to make it better than the original. To take advantage of the Sharp’s extra pixels, he modified the original code to display the game world in a 20×12 grid instead of the Spectrum’s 16×11 grid, allowing players to see a larger part of the environment. Incidentally, the original Atari version also displayed 20×12 tiles. In addition, he adapted the Spectrum’s version 1-bit beeper music to the MZ-800’s three channels, once again approximating the Atari original.