What's the difference between श śa and ष ṣa?
I can't hear any difference at all between श śa and ष ṣa. Are they actually different?
According to Wikipedia, श śa makes the sh sound we have in English (which is what it sounds like).
It also says ष ṣa is supposed to be retroflex, with your tongue pointing backward (like you do for ड ḍa or ठ ṭha. I can try making a retroflex sh, but when I do it, it sounds very different from regular sh. When the voice on Duolingo does it, I can't hear the slightest bit of difference.
What am I missing here?