We both thought maybe the dogs should be a bit quicker compared to the sheep. Also having the different dogs be identifiable in some way would be nice, we got a bit confused at times (but obviously appreciate this is early in development and you may well have planned both already). Knowing the number of sheep left (I didn't understand why they occasionally blew up in the coop sometimes?!) would be good as well as knowing how many each pen needed.
Again, you may well already have these things in mind. Nice work so far! :-)