Glad you liked it!
True, there could have been more emphasis on the red key (that's what I call it though it isn't really a key) being completed. The design for that key was actually changed almost at the end of the jam since its first form was quite a bit more confusing. At first it was supposed to be only one key for the red door but later I decided to split it into 3 so there could be a bit more of a sense of progress towards the end goal and my first design didn't really work for the split key.
About the map, I designed it with a drawing and then built each room separately in Godot. The process was a bit weird since the top rooms are upside-down on the drawing and passages from one layer to another could be offset when the layers weren't aligned. I'm happy it all worked out in the end though.
Also I thought about adding a second song for when you got all the red pieces but I ended up separating the current song into 2 tracks: 1 that played all the time and another that only started when you started the game and then stopped on the ending sequence to give it a more dramatic effect and loop back to the menu smoothly.