Thank you!
We developed the levels firstly "by hand", drawing them for instance on excel to have a grid just to have an idea. Then, on Godot, we had a TileMapLayer that was used to generate the levels and we mainly used that to test the levels without the need to actually play them, we just needed to draw the result of moves. Finally we also did some playtests on the actual game but the main focus was ar TileMapLayer level.
Puzzles were limited enough that removing shortcuts was easy, but many levels can still be solved in multiple ways.