With the redesigned non-tree [[skill trees]], there are no skill prerequisites other than the Clvl requirement for each tier of skills. These are set at Character level 2, 3, 6, 10, 14, 20, and 26.   ===Resource Costs and Cooldowns=== Skills in Diablo III vary greatly in their resource costs. Some low level skills have no cost, or a very low one, thus allowing players to [[spam]] them in all circumstances. More powerful skills have higher resource costs, to make using them more of a strategic choice. The highest level skills have very high resource costs, and/or cooldowns, forcing players to wait considerable times (up to 120 seconds for the highest level skills[http://diablo.incgamers.com/blog/comments/blizzard-on-high-level-barbarian-skill-cooldowns]) between uses. The point in resource costs and cooldowns is to give Diablo III's skills greater variety in effect and usage.[http://diablo.incgamers.com/blog/comments/blizzard-calms-the-masses-on-skill-cooldowns] In Diablo II there were very minimal cooldowns and resources costs became irrelevant to high level characters with lots of [[leech]], regeneration, or [[potions]]. As a result, every player could use their best skills constantly, without delay, and thus there was no reason to use lower level skills at all.  In Diablo III, lower level skills can be used very regularly, but they are not as powerful as higher level skills that have higher resource costs and/or cooldown times. Thus players must be more strategic in their skill use and selection, and the developers can make the higher level skills much more powerful than the lower level ones, without those skills becoming overpowered. Cooldowns also keep lower level skills viable, since players must use them regularly, while saving their bigger skills for special occasions. * See the [[cooldowns]] article for more detail, [[Blue]] quotes, and specific skill examples.<br>