It's nice to build a game for a friend, and to have him play your game and ask you questions about what path to take.

On the other hand, for us online players that can't talk to you while playing, clueless pick a path with instant death is no fun. Getting killed while crossing a room boundary and not being able to see what killed you is also no fun.
To make the experience better, you could shift the camera by half a tile so you can always see what you are stepping into.
For the path where you have to step on death tiles that can be real traps or fake traps, add sings with riddles that clue to the right path.
Alternatively, you could reduce the penalty from insta game-over to "leave a corpse" that can serve as a marker to the trap tile, and spawn a new player from the start, while keeping the keys. That would make the unavoidable death traps a minor set back instead of a major turn-off.

Nice job, I made the same game using the same tutorial, although I never posted it on here, but you went a lot further than I did on mine. Good job!
Also, when you touch a chest it gives you a key and opens the chest. You might want to fix that.

I edited the game to make the aforementioned changes, and even then couldn't get to the secret exit. I was short one key despite taking all the keys of the map and not wasting any.
To the top right of the 1st winning room there's collision missing, so you can go over the path to the secret ending. From there you can go up and wander around in the black void, but no hidden key there.
When going to the key at the bottom of the map, you can move into the black by abusing the diagonal mechanics+map boundary mechanics, but no keys there either.
Finally, I manage to redo the game from the start and skip the door from finish to secret finish by moving diagonally from above the door, but that's probably not the intended solution. I suspect the open chest is a map mistake and that's where you were supposed to get the missing key from.

Thanks for telling me that! I'll fix that in a bit

also btw the 1 key left was in a pot but i'm gonna retexture it so it can be a bit obvious that it's a key