One small note - it is singular for ciasteczko. And both this words are diminutive form of 'ciastko' (plural 'ciastka')
...which may look as another diminutive form of the word 'ciasto', and etymologically very likely is, but means 'cake' or 'dough', so let's not dig any further ;)
Teaching the Russian alphabet was a must, but teaching the sounds in the same-alphabet languages is a relatively new feature, one that wasn't available when this course was being created. Yes, I agree that it would be very useful, it's something that we'd like to implement in the feature when the course gets updated.