Cool concept! I like codebreaking games, and a multiplayer one is an interesting idea, though I'm not quite sure how this fits into the theme. As a proof of concept, however, it's neat, but needs some refinement.
For one, changing your own code should be on a separate button than space. Too many times I tried to interact with a node only to accidentally change my code.
It's hard for me to judge it properly, though, since there weren't many people online when I played.