I made a patch that lets you grind credits from nodes. You can download it here.
The way that the game currently works is that, once you've collected a [c] credit square, the game remembers this and won't let you collect credits from it ever again. My patch makes it so that you can collect credit squares over and over - as many times as you want. This way you can grind for credits by playing the same node over and over again, which IMO is a necessary and important mechanic to have in this game. (IIRC the original game had this mechanic.)
r_tsang's solution is clever, and it helped me a lot in reverse-engineering the game's code, but it's a little inconvenient: You have to manually run the code and then refresh the page every time you want to farm a node. My solution should work seamlessly: As if the game had been designed this way from the start.
I've 100%-ed the game with this patch and never ran into any issues, but please let me know if you run into anything, and I'll see if I can fix it.