There is already a bullet launcher - the spawner-bullet. I don't want to make new elements that repeat what's already there. This gives me an idea for a cluster bullet however - like the cluster-turner.
I have already considered other exit types - they could be shielded. They could be ally-doors that have to be released by scroll blocks or fighting. I am considering a key-passive for the puzzle mode (you must kill all key enemies to unlock the door). The key might be a good addition to endless.
The endless mode is not finished and neither is the game. The progression is a ramp upwards - whereas desirable progression should be like a sine wave. Developing an algorithm for this is very complicated and takes a long time. I have no intention of letting one finish the endless - you can finish ending, this experience already exists and does not need repeating. I am however considering achievements that one can search for, or quests. It's important to investigate a game experience that has no win state. I understand that a lot of people will be angry or upset that they cannot achieve closure. The point is to keep researching mechanics and play to find a space where a win condition does not need to exist. I don't expect this to be easy or quick to resolve.