Allow your players to have a sense of ownership

Magic has a property that it has multiple formats to choose from. Each format restricts what cards you can play with. The official formats are sanctioned and adopted in tournaments. But the players are free to create their own rules and formats. "Commander" for example was created by judges that wanted to have fun after long hours judging tournaments. Commander has its own set of rules and one of them is to restrict decks to have exactly 100 cards, not fewer and not more. The company saw the format growing in popularity over time and when it was clear that people loved it, they sanctioned it and started to sell pre constructed decks made for this format.

The lesson that Mark is teaching is that the players are more likely to embrace what they feel they took part in its creation. It's only natural for people to have a stronger connection with their own work. This applies to jobs, objects, art, children, etc. We could go further and discuss psychology and what makes a person feel attached to its own creation but that is another topic. Magic creates attachment through many channels. The most basic form is attachment in magic is the freedom to choose your cards and build your deck. Every player owns the cards and this really makes the game personal.

One of the reasons for Minecraft's success is that it allows the player to have power over the environment. The players are free to explore and create inside the game. There are many groups of players that build anything you can imagine in this game. From real world locations to continents based on real world satellite data. Games such as unreal tournament, quake and doom brought a trend of including modding tools and level editing tools that give the players freedom to create. There are communities dedicated to the creation of mods and maps and this allows many people to begin their careers in they want to dive in this world of design and development. There are some issues regarding copyright and the complexity of the tools provided but that's another discussion all together.

This site is a proof of Mark's argument. It's about level design and it couldn't have been made if not for games coming with level editing tools.