The application works with riddles and bite-sized questionnaires, so you can spend a couple of lessons every day when you have some free time. Log in with your Google account, review the basic coding definitions and then start the exercises. The more you advance, the more complicated the puzzles become. The application will also ask if you want to set a practice schedule and receive reminders, daily or a couple of times a week, so you do not lose the skills recently learned.
Grasshopper starts with what he calls "The Basics", which includes things like call functions, variables and strings. Each time you introduce a new concept, you get several riddles to practice. For example, an initial puzzle that deals with shapes asks you to draw the French flag. It shows what the solution looks like, and then a space where you can touch blocks of code to create a script that replicates it. Later courses cover more complex animations and functions using the well-known D3 library.
Grasshopper can be downloaded for free from the Google Play Store and the Apple App Store.