The IGDA Online Games Special Interest Group has noted that level treadmills are part of the addictive quality of MMORPGs that caters to those who play more than 25 hours a week. Another criticism of the entire leveling concept and level playing field approach is that it often allows the player to avoid difficult strategic or reflexive challenges that one might encounter when fighting powerful opponent challenges. By spending a large amount of time battling weaker or easily defeated characters (a practice known as "bottomfeeding"), players can gain levels to have little difficulty vanquishing the more difficult enemy.