I tried to use this for all of 5 minutes, then deleted it. There is an advertisement every 30 seconds, and they are the ones that you have to wait so many seconds before you can close out of it and get back to the flash cards! I love the set up, I liked the questions, but I do not have time for that many adds, and it breaks my focus every time. I realize it is a free app, and expected adds and occasional pop ups, but I can't even use it because of the constant interruptions.