Despite successful releases for DK'Tronics, such as 3D Tanx and Maziacs, Priestley returned to teaching in the late 1980s, claiming changes in the video game industry did not suit his style of work.
One of his early programs was an adaptation of Conway's Game of Life which was converted to a newly purchased Sinclair ZX81.
His first commercial game was The Damsel and the Beast, inspired by a program called Mugwump and published by Bug-Byte.
[7][8] This distinct graphical style happened by chance: The licensors, King Features - were at pains to point out that any game had to include fair representations of the central cartoon characters, so I sat down with a large grid and came up with a figure of Popeye which was seven characters high and six wide - 42 characters to move for each frame!In 1986, Macmillan Publishers re-released Popeye and approached[1] Priestley to use the same techniques on a launch title[9] for its new label, Piranha Software.
The Trap Door, based on the animated series of the same name, won multiple awards[10][11][12] from the press and has been described as one of the best games ever released for the ZX Spectrum.