Factorio. The game automatically adjusts difficulty based on your speed and familiarity. Pros scaling rapidly are going to have a harder time with biters than a noob learning the ropes on the exact same difficulty settings. Difficulty settings can be scaled up for a true challenge. Mods are supported damn near as much as first party devs. It’s a very well optimized game. It’s just technically impressive, psychologically fun, and fundamentally well balanced.