20: Most challenging but rewarding system you have learned?
I don’t really want a system to challenge me. If a system keeps hogging my attention I’m liable to use something less obtrusive instead.
I’ll make an exception for games designed with specific purposes in mind. Leverage maybe? It’s about telling an entertaining crime story rather than simulating crime, so the authorial distance of encouraging players to put their characters in trouble for later payoffs (and getting them out with player narrated Flashbacks) isn’t interfering with regular player to character identification. It’s still more moving parts than many players like to deal with though.