In the newer games that succeed the original trilogy, new gameplay elements were added such as levels in which the characters and foreground environments appear as silhouettes, spawning several new gameplay mechanics. In "Donkey Kong Country Returns" and "", collecting K-O-N-G letters will not award any lives to the player, but instead unlock various bonuses and hidden levels. Additionally, in these games collecting puzzle pieces unlocks artwork from the games. In "Tropical Freeze", the Kongs are able to pluck items from the ground and pick up and throw stunned enemies. Additionally, filling up a 'Kong-POW' meter allows Donkey Kong and his partner to perform a special move which defeats all on-screen enemies and converts them into items depending on the partner.