The look and feel of this app is top notch though there are a few issues with it at least on iPhone 7 running iOS 11.3. 1. Currently on the lessons I’ve tested (JS and REST API) the slides sometimes fail to render both text and “fill in the blank” sections but that usually can be corrected by quitting the lesson or app and relaunching. 2. This may be intentional because I’m not subscribed yet but the Exp progress bar does not update and is stuck at what looks like 95% with 3200/2500. This app still gets 5 stars for me because it has clear and to the point content and looks and feels better designed than all of the other “code learning” apps out there.