I am using this method mentally... Now I do it in Chrome Android SPA.

In round 1 (for level N), you speak N random words In each next round, you repeat the last N-1 words from the previous round and append 1 new word at the end. he app stays out of the way: on success it just beeps (or says ok, you can put it off that voice...), and on failure it only reads back the N-1 words you needed to repeat.

I tested it in Chrome Android.

Thanks!