Using the browser's speech recognizer as a pronunciation judge

Pronunciation scoring APIs charge per request and want your audio on their servers. We teach spoken English to learners in India, mostly on phones, and we wanted a free test that costs us nothing to run. So we let the browser's speech recognizer play the listener. The idea: minimal pairs Vest and west. Thin and tin. Ship and sheep. Each pair differs by one sound, and that's exactly the sound a lot of learners merge. If you say "vest" and a speech model trained on thousands of speak