My first impression was "omg they can run fast!". And I used my bad habits and did not use the wall as intended until days ~20ish.
This build is already robust and pretty interesting (-> edit: sometimes the peasants bodies remain in the field even though I did not use any weapon and the bats will stay nearby). And in some case, the push back is so powerful the peasants are in fact pushed closer to the castle lol.)
But I was a bit disappointed by the bats, once I used an archer, I found out they only care about 1 target and once it is destroyed, they go back to their spot until they found another one nearby. Knowing this, it can be worked around, though.