An English book in which part of the words are Russian. How many is up to you — a ring, from zero to a hundred per cent.
Nobody translates the sentence for you. The English frame holds the grammar — the article, the word order, the preposition — and your head fills in the noun from what is around it. When it does not, one tap shows the word, its part of speech and how it is spelled.
Start at five per cent, where a Russian word turns up once a paragraph. Move the ring when that stops slowing you down. Above sixty per cent the app starts replacing function words too, and what is left is a crib rather than a book — the ring says so when you get there.
An unfamiliar alphabet turns every replaced word into a hole in the page, so the alphabet is a setting, not a wall. Latin spells the word the way you already saw it in Gorbachev and borshch: krovat'. Both shows the two together. Cyrillic is where you end up: кровать. Switching is instant and does not reshuffle the page.
Three days without limits. After that ten pages a day stay free, and a single purchase removes the limit for good. It is not a subscription: nothing renews, nothing is charged again.