About Additive.
What is 3+2? Sounds easy.
Now 4+3 is it 7 or 6 ? Again easy.
What if you have to answer with 2 seconds or else it is game over, not as easy as you think.
Additive is all about checking if the sum is right or wrong with right/left swipes (Tinder like). The longer you go without wronging, the bigger your score.
(The rumor is that if you get a score above 100 your IQ is over the roof).