I’m TDY Chicago for a couple of weeks for business and using my of hours for code practice. I found a Android CW training app that is the best I’ve seen so far. It has crisp graphics, good audio, Koch, Farnsworth, simulated QSOs and the rest. I down loaded it for $2.99 from the Amazon App Store. It is labeled CW Trainer and Morse Trainer. I’ve downloaded others that work but they are not nearly this nice.