The controls are:
Any key to start (gives the randomizer time to cycle)
Cursor keys to select a number, zero to select, then press a cursor to swap in that direction.
Press 1 to reset the game.
It runs on emulators, but also on a real ZX81 with the ram pack pulled out.
Here's a link to a Youtube video of game play
My web page also has an MP3 you can download to try it out on a real ZX81
I wish I had this game when I bought my 1K ZX81 in 1982. I had to save for the ram pack otherwise I could barely do anything with it. Hope you all enjoy the game!