I find this very easy once you hear the pronunciation. I was worried that it would not follow the planetary pattern like the romance languages do, but it does in a way even more similar to English than those!
Accents (in English as well as in Welsh) do vary across Wales.
The pronunciation of u and clear y does change, gradually becoming 'darker' (more like /ɨ/) the further north-west you are. The computer-generated voice on Duo has a neutral accent that does not use the darker sound.
To hear the difference between someone from (probably) mid south Wales and someone from north-west Wales, watch the series of pronunciation videos that we recommend - look on the web for 'welsh plus pronunciation youtube'. You will notice that their English and Welsh accents are both different.