Problem
I wanted a multiplayer game that kept moving while you weren't playing it, but most idle games are single-player and most multiplayer economy games require everyone online at once to feel alive.
What I built
A multiplayer idle market game where players run competing firms producing and selling goods into shared markets. Prices tick automatically on a server-side schedule, so the economy keeps moving whether or not anyone is watching. Production accumulates while offline. The win condition is completing a megaproject that requires sustained investment across multiple resource types, which forces players to plan rather than just check in once and walk away.
Hardest part
Keeping the shared markets stable with a small player count. With only a handful of firms, one player dumping a resource can swing a price far more than it would in a larger market, so I had to add server-side dampening without making the market feel rigged.
What I'd change
I'd build the megaproject system to support partial collaboration from the start. Right now it is mostly a solo grind with shared prices, when the more interesting version would have players actually need each other to finish it.