To make sure that several Karas never work on the same block of cloverleafs, all states in which a Kara is standing on a cloverleaf are critical section states.
First, the Karas have to find a block of cloverleafs (state "search"). If a Kara finds a block (i.e. he is standing in front of a leaf), he acquires the critical section and then steps on the field with the cloverleaf. He walks to the end of the block (state "to the end") and replaces the cloverleafs with his own (state "replace"). Afterwards, he leaves the cloverleaf block and releases the critical section.