I’ve been playing SET for the last fifteen or so years, mainly as the card game, and it’s always been one of my favorites. I like the app a bit more, as the portability is unbeatable. There are some things to know, as the game, like all games, has a couple quirks. (Also, I only play Classic SET with the advanced deck.)
First, there are not always sets in a given group of 12 cards, which can be frustrating if you’re new to the game. (1/33 chance, I believe.) If I don’t think there are any, I’ll start from the upper left and scan starting from card to right and all the way to end, repeating with next card (since any two cards have exactly one card that can make the three a set). Second, the way this app rewards with one, two, or three stars is intense! It takes some luck (i.e. no or almost no no set groups) to get top marks. It will take some practice to get even one star. My record is 9.6 seconds per set, but i average around 14 or 15.