The hyperspecificity of learning is a vexing issue when designing interventions for cognitive enhancements. However, playing a certain type of video games (Action Video Games), but not other games, leads to robust and long-lasting benefits on a wide variety of cognitive tasks seemingly unrelated to the games, and specifically on tasks of attentional control. We first give the theoretical foundation for the hypothesis that it is the combination of a high pacing, load on divided attention, and load on focused attention, that is it at the source of the aforementioned cognitive enhancements. We then present how we designed different versions of the game implementing the features to different extent in a gamified dual multiple object tracking task to test this hypothesis. Finally, we present the results of a feasibility study where we train more than 125 participants for 12 hours over 4-6 weeks in a fully online fashion.