I have a question. Will there be secret goals you'll need to fulfill to unlock the enemy gallery like in ppg?
Yes, more or less. The current idea is to have "totems" or tokens (collectibles) of each enemy type hidden through the stages, and once you collect the token of a certain enemy, they'll become available int he gallery mode. Some tokens will be placed very visible and in easy to get places, while others will require a bit more exploration or puzzle solving.