Hey thanks a lot for playing my game and I am glad you liked its graphics and music.
and about the collision boxes,
Here's how I managed them:
Instead of using the collision of the objects itself, I made a separate tiled sprite for collision and in the events I just added: [When player is in collision with collision box: separate player(only player will move)]
Also for vertical walls, what I think amazed you is that when we stand on the back side, the wall is on top and when we are on front the wall is on back. To do this I added all such objects to a object group called "Zobjects"(you can name anything). Then in the event I added 2 functions,
1. At the beginning of the scene -> set Z Order of "ZObjects" to Y position of "ZObjects". (So this way every object now has a unique ZOrder based on their Y position, Now if I place a table just below the wall then at the beginning of the scene because the table has Y position higher than that of the wall, the table will appear in front of the wall) (because in GDevelop as we move towards bottom direction, value of Y increases ) (NOTE: Don't add the ground to the group "ZObjects", we want the ground to be always at the bottom so simply set it's Z order to be in negative)
2. Now we have the Z order of objects figured out, but player still has a fixed z order. To fix this we add an event to run without any condition such that: [change Z order of player to Player.Y()] (This way if if player goes beneath a table then it will appear to be in front of the table and when it goes back then because the Y positon of player decreases, it will appear on the back of the table)
and if you were amazed by the fact that the feet of player is aligned perfectly with the bottom of the wall, then that is because I placed the collision boxes to be that way.
I hope I was able to help.