Baseball’s infield fly rule seems strange at first. It says that when there are runners on first and second with less than two out, and the ball is popped up to the infield, then it’s an automatic out, even if the fielder drops it. Without the infield fly rule, the fielder might let the ball drop on purpose. Then they could turn an easy double-play at second and third base. A pop-up would turn into two outs in a way that isn’t fun for the players or fans because it takes no skill. The rule is there to make the game more fun.

Professional sports are filled with rules like this. Basketball has goal tending, soccer and hockey have offsides, and in football, you can’t catch a pass if you run out of bounds. Rules like this often come after their absence was exploited. For example, goaltending was introduced in 1944 to stop a 6’ 10” center from making the game less fun for everyone (else).

So, when designing an infinite game, you might need seemingly arbitrary rules. Probably it’s better to notice when the game is too easy and figure out a way to make it harder. Based on the examples above, you should also look for times when you play the game in an odd way that gets you rewards with no skill or work. It might seem fun at first, but easy games get boring, and then you’ll quit.