One thing I considered while working on "multiple edition" support is whether to consider Volume 3 as a separate "index". Doing so would be interesting as the progress chart could focus more specifically on one book. However this causes problems in the Study page. Say I have selected "Volume 3, 3rd edition" (800 kanji), what if I want to go to Study kanji #600 ? This one isn't in the #2201-#3000 range.

Logically it seems 4th and 5th editions of RTK Volume 1 are followed by The 1st or 2nd editions of Volume 3, for a total of 3000 kanji. That would be the "old edition(s)" index.

The "current editions" index presumably will be: 6th edition of Volume 1 (#1 - #2200), followed by 3rd edition of Volume 3 (#2201-#3000).

Can I even assume that most everyone will have the correct volumes as above? If you have an old edition (up to 5th) of RTK 1 then you should probably get an older edition of RTK 3, otherwise the 196 or so "newly approved kanji" added in 2010 won't be covered. Then there are still 23 missing kanji which until today are available on the site as #3008-#3030. Those are from the 196 newly approved kanji that were not covered by RTK3.

If you have a newer (6th) edition of RTK1, then you should follow with the 3rd edition of RTK 3.

So to summarize so far: if the user selects old edition sequence, it will be as it is now: #1-2042 (vol 1), #2043-3007 (vol 3), #3008-3030 (remaining newly approved kanji missing from Vol 1 & 3 ). If the user picks current edition sequence, it will be #1-2200 (vol 1), #2201-#3000 (vol 3).

I hope that makes sense for the users, because it's definitely not intuitive for me. Fortunately switching between editions on the site will be harmless: it will not affect any stories or flashcards as these are all using the unicode character as the unique reference. This may be handy later if I add "RTK Lite". The user could then start with RTK Lite. When they switch to the full Volume 1, adding flashcards will fill in the gaps. New cards will appear in the blue pile, any existing flashcards will stay where they are in the SRS.