These are problems of the mate in X variety. For example the first one 8/8/8/p7/kPr4R/N1P5/2P5/1K5Q is by A.Myers, 1882. There are three issues with this app: (1) They do not credit any of the composers. This is beyond annoying, it is simply NOT DONE. One star for that alone. (2) They do not give the stipulations, in this case "mate in 2". (3) They do not give the correct solutions, for this one it is 1.Qd5. The app seems to calculate the solution on the fly, the first time it gave mate in 4 starting 1.b5+, the second time mate in 3 starting 1.Qa8. I looked at a sample of the other problems and it is the same story.