Very cool, though wouldn't using durable objects for a MMO type game become prohibitively expensive vs using websockets with a stateful server? I assume your game is not sending that many requests so its not too bad.
websockets + stateful server would be the right call for anything realtime. for tick-based strategy with hour-long timers, DOs feel like the cleanest fit - i get per-island isolation, alarms, and storage in one primitive without managing a connection pool.