This is the place where you can leave a question if you get stuck in a puzzle and I will either tell the answer right below or fix it if it's actually broken

Library bronze key button co-op:
the button is a puzzle where all players have to stand on it at the same time.
I will put some text on it in the next patch but I will wait until something game breaking happens. thanks for the feedback

Library level 2 offence vendor access:
this is a secret shop that you can access from a button found in the bottom left corner of the vertical bookcase room (after the horizontal bookcase room), however this shop becomes inavailable once you get the bronze key mentioned above. Don't panic though, there will be other offence shops in the not so dinstant future and you save money. This shop is just so you can get a bit over powered for the next area. (I thought the button was cleverly hidden too)

Secret endings and bonus level:
there are 3 slightly different endings in addition to the "normal" one that can be activated when you find all the 4 runes. All runes can be found in the levels that the Intersection level leads to: Library, Old quarters, Ancient quarters and Caves.
-In "Library" go to the most bottom left corner. It's available there without any tricks.
In the "Old quarters" press all the wall buttons found in the leftside of the level and a passage opens just below you.
-In "Ancient quarters" you must press the wall button in the bottom left corner (beyond the fire spitting pillars) in order to open the shop located near top left corner that has a button which opens a wall back in the first button. Then just follow the money.
-In the "Caves" you have to hit the right side wall in the top right corner of the map (where the lonely button lies).

All these runes can be seen in the backdoor level at the very beginning of the game through a dithered ceiling.
In addition when you get to the "Top" level, you need to find the bridge now available after getting all the runes (notice the text: "You can feel the runes stronger"). This bridge is located at the left side of the map.
You fight some bad guys and press a button. (you get the text "you can hear gates opening below").
Go to the "Gates" level and proceed to the middle of the map now available and push the button. (you now get a text "you can hear ice moving below").
Go all the way back to the "Caves" and head down where there is/was a gold door.
You DO need another golden key if you used the one on the level itself on the other golden door. (available on the top level assuming not used on the final boss doors.)

Now you are in the bonus shop area. Just visit every pillar and the hatch opens.
Now you are in the bonus level.

In order to get different ending #1 you just exit with all: gold, silver and bronze keys you got from the "Top" level, and use them in the escaping episode.
To recieve ending #2 You need to hit one of the flashing floor sprites in the bonus level just above the level exit to open a secret exit in the beginning of this level.
And to get the last ending #3 you do the same but don't need/use the keys during escaping.