Not good, but you can use as an additional help
This not a perfect fit for someone who start from the very beginning and need to drill like basic stuff. After explaining really long and complicated rules they give you exercises where they mixed all at ones. And no option to go back to theory and look it up again. For something very important and tricky as modal verbs there is only ONE exercise with no in-use peculiarities. It’s absolutely not enough. At the same time like thousand exercises on plurals with words that one will probably never use. Like fingerprints. Who in this world would learn the word fingerprints on A1 level? When you are unable to say your name properly. But at some point this helps to drill some stuff. So in a nutshell use this app as an additional.