Thank you for your kind comment! I indeed thought about a difficulty selector, but didn't have time to implement it. I even had names for the diffuculty levels, from "freshwater swab" to "bloodthirsty scallywag".
Right now the opponents are pretty dumb, it's obvious after a few plays. I thought about a simple decision tree that would give every opponent better bets and a bit of personnality, more cautious or aggressive. But again I was out of time. I also thought about more opponents, but that was clearly out of scope from the beginning
Regarding online multiplayer, I guess it could be done but at the moment I'm far from having the required knowledge with Godot.