The problem is just that you're concatenating a 1d array with a 2d array. All that needs to be changed is b = [c] ~ b; since then it's concatenating [[bullet,bullet,...]] and [[]].
[[a,b,c],[d,e,f]] ~ [[1,2,3],[4,5,6]] -> [[a,b,c],[d,e,f],[1,2,3],[4,5,6]] and so on.