Next time either make the multiplayer more accessible without needing to let the player set it up or add a single player mode because most of us probably won't have a friend to test this with.
Viewing post in Zero Sum (NeuroJam version) jam comments
(Very late reply but replying anyway for posterity)
I actually did want to have a single player mode initially, but as a solo project and my first game jam, I didn't end up having the time to implement it, and multiplayer was much easier to get working. I wish I could have at least had a permanent server set up, but I didn't want to be responsible for it going down during testing (and I actually ended up having internet dropouts during the review period that are still ongoing now), and didn't exactly think it was wise to provide an accessible IP to The Swarm in any case.
Definitely something I'll keep in mind for the future though, and something I want to do if I revisit this game.