Oh! That was meant to be my Master research project! It was based on Cyclic Dungeon Generation by Joris Dormans, to generate a Zelda-like dungeon with “keys” and “locks” where keys had to be obtained before being blocked by all locks - but a Metroidvania world works the same map.
I was however working with polygonal rooms and had some issues placing the rooms while avoiding collisions, so I ended up making a thesis on irregular polygon packing.
But I see how the last steps switch to a tile-based map, that makes things much easier!
I would generally ask for source code but it seems that this was done in ClickTeam Fusion so I’m not sure how portable that would be (I’m not familiar with this engine)
P.S.: next time instead of Metroidvania x Magical Girl Game Jam, we should have a crossover Metroidvania x PROCJAM