How I use open source to design my own card games

I love a good game, and I particularly enjoy tabletop games because they have many of the same traits that open source has. When you’re playing a card game in real life with friends sitting around a table, you can as a group decide that Jokers are wild. Alternately, you could arbitrarily decide that should a Joker come into play, anyone holding an Ace must discard that Ace.