Fun, and a programmatic perspective. However, it can be too easy and fun to get super caught up in these details, if your goals are some level of fluency and ability to communicate/read. The majority of people that I know who have gained any level of fluency in Japanese as an adult mostly avoided stuff like this because (for many people; of course everybody is different) doing all of this mental math to dive down to the last detail was nowhere near as effective as some speaking and reading drills.

It is definitely well written and presented.