Basically it's a game where you pick the friendly face as quickly as possible out of a grid of unfriendly ones. The theory behind it is that people with low-self esteem, depression, and social anxiety (hi, nice ta meetcha) tend to be mentally trained to seek out and react to negativity first, often to the point of being unable to even register the positive any more.
I played the game and was kind of surprised to find myself having to go over some of the grids three or four times before I could find the smiling face. Sometimes it was kind of a gyp, because they're often being deliberately misleading or distracting regarding standard facial cues: all the expressions have the eyes crinkled, which is usually a visual glue for smiling (anger and fear are very often wide-eyed or normal eye size), several of the angry expressions have the teeth exposed in a snarl (which catches the eye when you are looking for visible teeth in a smile), some of the smiles are tiny little smirks, yadda yadda. But some of them I didn't see at first even when the person had a huge toothy "HYUCK!" grin on their face. So, there may be something to their idea of being able to re-train the brain with this game. Snapping focus to the negative is a good thing for problem-solving and crisis-handling situations, but it's not a good way to constantly live my life, especially if I'm really becoming unable to see the good things. Which I really feel that I am.