The 4th edition heavily retooled the class system in favor of a more unified set of mechanics for characters, which was in part intended to reduce some of the perceived imbalance between spellcasters and non-spellcasters in the 3rd edition. Classes can be defined as the combination of a character role with a power source and are differentiated by what active-use class features and powers they give, all of which follow the same pattern of at-will, once per encounter, once daily and utility powers.