Someone on World of Spectrum has pointed out a ZX81 game - Maze-K which appears on http://www.zonadepruebas.com/viewtopic.php?f=15&t=4646
There are a few more games on those forums:
Sodoku (1K) - http://www.zonadepruebas.com/viewtopic.php?f=15&t=3904
Mine Field (1K) - http://www.zonadepruebas.com/viewtopic.php?f=15&t=3878
Lights Out (1K) - http://www.zonadepruebas.com/viewtopic.php?f=15&t=4161
Not sure if these are the same versions which have appeared on here....
Maze-K
Maze-K
Rich Mellor
RWAP Software
RWAP Adventures
SellMyRetro
Retro-Printer Module
Also Involved in:
Icephorm
RWAP Software
RWAP Adventures
SellMyRetro
Retro-Printer Module
Also Involved in:
Icephorm