The reason Duolingo is ineffective in my opinion is multi-faceted. First, my main language for study is Japanese, and Duolingo's Japanese course is awful - these are the specific things I noticed when trying it: - There were several factual errors in their material and important points entirely omitted - Japanese grammar is very flexible and their tools aren't, so they often mark you as wrong when you were correct -…
...trying to cram their prepackaged square-shaped tools into a variety of circle-shaped holes. All languages are different and each requires a different approach. The first half of this is dead on. The second half is wrong. Duolingo's top languages are in the Indo-European family. (Their most learned language is English, next is Spanish.) Their techniques are perfectly adequate for gaining elementary vocabulary a bas…
- Different meaning: Es un pobre hombre (pity). Es un hombre pobre (poor).
- Same meaning: Tienes un excelente humor. Tienes un humor excelente. [1]
- Emphasis: ¿Ya os habéis mudado a la nueva casa? ¿Ya os habéis mudado a la casa nueva?
In your specific example, "negra camisa", while it is valid it does sound archaic. However this does not mean that ADJ+NOUN are wrong in Spanish. Not at all.
Edit, more on the topic here: http://adjetivos.org/adjetivos-especificativos-y-explicativo...