KAI Japanese Language School has been using digital textbooks since the introduction of iPads in 2015.
At first it was just a textbook of data, but each semester it has been upgraded, adding exercises and changing the style. In 2019, we started changing from vertical to horizontal layout, and the textbook Maeda House, which was a separate volume, was included in the main textbook. And this year, finally all the textbooks for levels 1, 2, and 3 are now horizontal!
After making the layout horizontal, the kanji readings (rubi) were placed underneath the kanji. This decision is based on research that shows that for those with dyslexia, the reading is easier to read this way than that above the kanji.