“…Twelve of the papers reviewed [2,4,6,9,10,11,18,19,20,23,34,35] used the term "game element" to describe the low level implementations they use, such as points, levels, leaderboards, progress. Four papers from the same authors [25,28,29,30] use the term "game features" to present the same level of implementation. Knutas et al [21,22] use the terms "game like elements".…”