Complexity in games: rules that increase skill expression

I've been thinking about games and their rules. This kind of came up when I started learning poker. I was playing online poker and I was confident I had the best hand. When the cards were shown, I won! But then the game moved the pot towards my opponent. It turns out my opponent made the "wheel straight." A straight is poker hand made of five consecutive number (rank) cards. For example, 9, 8, 7, 6, and 5. The highest straight you can make is Ace, King, Queen, Jack, Ten (because Ace is the highest card). The lowest straight I thought you could make is 6, 5, 4, 3, and 2, as 2 is the lowest card. But much to my shock, the lowest straight is the "wheel straight," made of 5, 4, 3, 2, and an Ace. This rule of allowing the ace to act as either a high or low card is very interesting to me.