This game is named Gather! Kirby (あつめて!カービィ Atsumete! Kābyi) in Japan and was released in 2011 (Japan first in August 4, then America in September 19, and finally to Europe in December 1). This game was published by Nintendo and developed by HAL Laboratory. Just for extra, if the title, Mass Attack, becomes katakana, then it will be like this (カービ
ィ マスアタック Kābyi Masu Atakku)