Ok memory game! Very basic but I can tell this is a practice game project you made. It's great that you start with simple projects!
I think you could add some flare to this by giving the player a little score bonus for clearing puzzles faster/fewer moves. That would give the player an incentive on getting better at the game.
This is a small thing - but please consider using shapes rather than colors. Even though this game is some colors that are different in contrast - it's still going to be hard for color-blind people. And color-blindness is more common than you might think.
I'd also suggest just putting up the full game on NG and not do a promo like this. I guess it's a free game on GooglePlay anyway?