widely known and lead to players changing their play behavior appropriately. This self-balancing force should not prevent developers from intervening in extreme cases of imbalance though. Positive and negative feedback Positive and negative feedback, also called positive and negative feedback loop, essentially describes game mechanics that reward or punish playing (usually well or bad) with power or the loss of it. Therefore, success leads to more power within a positive loop and therefore accelerates progress further, while a negative loop decreases power or adds additional costs to it. Feedback loops should be implemented carefully to only target the correct player, or otherwise they might determine the outcome too early or achieve nothing but simply delay the end of the game. Many games become more challenging if the player is successful. For instance, real-time strategy games often feature "upkeep", a resource tax that scales with the number of units under a player's control. Team games which challenge players to invade their opponents' territory (football, capture the flag) have a negative feedback loop by default: the further a player pushes, the more opponents they are likely to face. Many games also feature positive feedback loops – where success (for example capturing an enemy territory) leads to greater resources or capabilities, and hence greater scope for further successes (for example further conquests or economic investments). The overall dynamic balance of the game will depend on the comparative strength of positive and negative feedback processes, and therefore decreasing the power of positive feedback processes has the same effect as introducing negative feedback processes. Positive feedback processes may be limited by making capabilities some concave function of a measure of raw success. For example: In RPG (role-playing games) using a level structure, the level attained is usually a concave transformation of experience points – as the character becomes more proficient, they can defeat more powerful adversaries, and hence can earn more experience points in a given period of playtime – but conversely more experience points are required to 'level up'. In this case, the players level and perhaps also power does not improve exponentially, but approximately linearly in playing time. In many military strategy games, the conquest of new territory only gives a marginal increase in power – for example the 'home province' may be exceptionally productive, whereas new territories open to acquisition might only have by comparison slight resources, or may be prone to