There are many internal rules that need to be addressed when Wizards of the Coast designs new Magic: The Gathering cards, such as respecting the color pie and considering what a given card's effects bring to the table. For example, while all colors in Magic: The Gathering have some form of removal, they differ in themes and average costs to represent the philosophy behind the color pie and the various color combinations. Planeswalkers shook up Magic: The Gathering's gameplay in big ways over the years, and while they were introduced as mono-colored cards, they eventually started populating sets in more color combinations.