qu: the u is always silent and qu is followed by i or e. It is still a systematic way of reading. It is like gue and gui, you pronounce as in "singer" the "ge",

qu: the u is always silent and qu is followed by i or e. It is still a systematic way of reading. It is like gue and gui, you pronounce as in "singer" the "ge", the u is mute. If you want to pronounce the u, as in pingüino, you set the diaeresis. The stress rules, to the best of my knowledge, is very systemaic (not 100% but I would say "almost" at least for the words in use). Even the stress rules are very uniform. > r and rr are distinct sounds but r = rr at the beginning of words, I think. This is still systematic reading. At the start of a word it is the strong one, yes. And when it is preceded by a consonant, such as in "enredar" (that is strong r). There is no exception of any kind here. > d has a sound a little like English voiced-th at the end of words (e.g. juventud) That is some dialects in some areas. We pronounce a clean d at the end in my area (around Valencia). It is also the correct, standard way to do it for spanish. The other is a deviation existing in León, for example.