CO-GM

The @note_name syntax was a nightmare to implement. When you create that link, it's clickable, and if you edit the name of the link, all the references to it have to also update. It's not like a normal markdown link where you just update the URL—here the text IS the URL, which makes it a lot more complicated. Writing custom markdown where an @ symbol turns something into a clickable link, but then deleting parts of it intelligently updates the link across all notes in the entire campaign.

These were completely customizable calendars. Each GM can create a completely customized calendar for their campaign with their own number of weeks, number of days, number of months, every month with a different number of days. It supported all of that jazz, and that's just like a giant freaking mess. Keeping track of how Monday is a different day of the month, and those days are different per month each year as well. It's hellish. The system handles custom week lengths (e.g., 8-day weeks), custom month lengths (e.g., 13 months, 28 days each), and recurring events (e.g., always the third day of the fourth month of each year, or always the second Monday). All of this required a whole bunch of really annoying modulo math.

Built a rating system where users could publish calendars, compendia (encyclopedias/wikis), and random tables to a workshop. The data structures were kind of annoying because I was using a NoSQL database—I had to store the score both on the object that was in the store (for performance) and also save the score on the user. When someone subscribes to another user's wiki, all those pages become linkable from their own notes. That's kind of a headache to set up.