“you didn’t have enough time” (at about 15:50) is apparently “chest ti ddim”. But in earlier challenges, we had "ges i, gest ti,…) so why is there suddenly an aspirate mutation now?
Grammatically correct for negative clauses is in fact the so-called “mixed mutation”: aspirate mutation if possible, the rest get soft mutation. However this rule isn’t always observed in every day speech, so many people will just use a soft mutation even for c,p and t.
So in real life you may run into both forms, ches i ddim and ges i ddim.
(One form where the aspirate mutation is still in wide usage is in the “no”-answer to a question asking for permission: Mam, ga i fynd allan i chwarae? – Na chei!)
Thanks, Hendrik! So it’s being negative that does that? So “Ges i amser da”, but “ches i ddim amser da”?
Yes, negative clauses start with this mixed mutation.
Questions always start with a soft mutation, and positive statements don’t need any mutation, but many speakers put a soft mutation nevertheless. So:
Question: Gest ti amser da ddoe?
Positive answer: Do, ces i amser da. / Do, (fe/mi) ges i amser da.
Negative answer Naddo, ches i ddim amser da. / Naddo, ges i ddim amser da.
(fe and mi are particles that mark a clause as affirmative, and they cause soft mutation. So basically sometimes the particle is dropped, but the mutation stays in place.)
Thank you again, Hendrik! That makes sense and is very helpful!