Documentation to starting development in Zimlets for Zimbra 8

Hi dears,

Is there some documentation related to Zimlet Development in Zimbra 8?

I've found a lot of documentation for other versions, but no one fits and, until now, not a single Zimlet I was able to make work!

I'm not asking for some super complete and advanced documentation, one simple example for a tab, a button e a panel would make me very happy!

My hopes,

Fábio Coelho