This version of the Wizard of Oz uses Lettrd. Lettrd adds marks and, optionally, colors to indicate the way that letters are pronounced.
This interactive book allows varying amounts of phonic assistance to be added to English words. (Best with latest Android-System-WebView: see Play Store)
1) silent vowels ->
2) vowel names -> e.g. sy, m, fnd, mst, mic
3) =oo proved -> prvd
4) =e many, said -> mn, sd
5) =sh sugar, sure -> g, r
1) Common words can be gradually excluded (left unmarked).
2) There is a page with all the marks. Clicking the mark plays the sound
3) Vowels can be marked red; voiced consonants can be marked blue
4) The marks can be individually switched on and off.
5) Common patterns like 'sh', 'ch', 'ea', etc can be left unmarked
This is an old concept and was used in 18th and 19th Centuries in many reading text books. The interactivity is enabled by web technology.