This is an amazing app... if you’re a linguist. It’s still a very good app if you’re not. You can get a wonderful perspective on how Proto-Indo European evolved into many of its child and grandchild languages. You can see the evolution, with excellent audio pronunciation, in individual stages, such as Proto-Germanic between Proto-Indo European and modern English.
Almost all of the examples come with audible pronunciation, which is extremely helpful. I did dock the app half a star in my rating, because of all the languages and proto-languages, the only one without audio pronunciations is Lithuanian. This is disappointing because of all contemporary spoken languages Lithuanian is generally considered by linguists to be the closest to Proto-Indo European. Hopefully that audio omission will be rectified soon in an app update.
But this app should come with basic pronunciation guides on some of the more obscure sounds, and here is where I critique this app another half star on behalf of anyone who is not a linguist. You need to be very familiar with IPA symbols and their corresponding sounds to fully understand some of the language evolution this app demonstrates - especially for disentangling a sequence of obscure sounds in the audio pronunciation.
For example the symbol that resembles a question mark (without the dot) is the IPA symbol for a glottal plosive. Since that sound exists in (I think) none of the contemporary PIE languages it would be VERY helpful if the app had a page simply providing audio samples of the sounds each symbol represents, especially if that sound doesn’t exist in contemporary English. Ditto for, among others, the reverse question mark symbol that represents a pharyngeal fricative. Non-linguists will thank the creator for a symbols sound page, with correct audio pronunciation, in an app update. You can look up the pronunciation for any of these symbols easily online, but for the non-specialist that means regularly toggling back and forth between the app and an external webpage.
Also, if you’re not a linguist a lot of specialized linguistic terms will be inaccessible. For example, when the app shows a language shift between two stages of a language, would you understand the cause of the shift if all the app tells you is that the shift is due to analogy? Few people who are not linguists would know what is meant by a language shift due to analogy. It would be VERY helpful if the app creator made a page in the app that provides a brief summary of what is meant by these varying specialized linguistic terms. A brief explanation may not due these terms justice, but it would still be extremely helpful for the interested non-linguist.
I know this is a first release, and that’s why there are only examples in all the languages for just a few sentences, but I’m hoping that in an app update the creator will expand the number of sentences evaluated. I would especially like to see new example sentences that included terms and vocabulary that would have been central to the worldview of PIE speakers. For example, sentences that included words for time, the sun and moon, stars, the soul, soil, copper, bow and arrow, bears, wolves, hunting, chariots, twins or (duo) pairs, poetry, birth, death, marriage, and many more. Picking the vocabulary for new examples should be done in the light of elucidating terms fundamental to the daily worldview and concerns of the original speakers. In the current release terms like “fire” and “horse” and “cow/cattle” do this well. Those concepts would have been in daily usage by original speakers.
I also strongly believe the app could benefit from a brief explanatory note from the creator as to why he has posited a proto-language from which PIE and Hittite both descend, rather than Hittite descending from PIE. It seems this distinction is the thrust of his current research, and since this theory is not universally accepted in the field of historical linguistics a brief rundown of why he posits the language evolution in this way would be interesting and helpful. I know he can’t boil it all down to one paragraph, but within a single page (like an intro summation of an encyclopedia entry) I think he could give us the gist of his theoretical approach.
So overall this is an amazing app. I don’t give it five full stars due only to its lack of explanatory material for non-linguists, and its lack of audio for Lithuanian. I eagerly await an app update that will hopefully provide new example sentences.