ZX Net, the simple network for ZX Spectrum, is pretty much unknown feature of ZX Interface 1 (IF1) peripheral. A very few "network" games have been developed - mostly due to the IF1 price and required short distance between two daisy-chained computers. RS-232 is a better solution for two computers only game because it was standard modem interface at the time, but ZX Net approach makes tournament very feasible.
The game does not require speed so it runs in Basic.