Here is a little update...
We have added 6 new attackers to the Galaga Essentials. I was mixing up the art from our spacepacks 1 and 2 in combination with the Galaga pack to prototype this project but with the new sprites it will have a more consistent look.
Also updated the other asset packs and added a tool that we have named the SHMUP Builder for Unity. I wrote the docs for it but I will add tutorial videos in the next couple of months. More about the SHMUP Builder here.