So to give you a little more to go on, there's essentially three envelopes just hidden throughout the game. They can be hidden anywhere from slightly sticking out from behind something on a wall to floating I'm something else. Sorry for being a bit cryptic but don't want to spoil it too much for others. Hope that helps. :-)
Oh excellent! There's three endings in total. The mailboxes each need a "Strange Invitation" specific to each. These are hidden in some scenes of the game that won't show a label to the player when next to them. Same can be said for the other hidden interactions that provide another ending. Happy hunting! :-)
Oh good eye. Nothing that will alter an ending in that room. That was more of a touch of environmental storytelling with the inhabitants of the house trying to contain the growth that had taken hold of one of their own. As you can see so far, it hasn't exactly gone well for them. Really glad you've been exploring so much. Hope you're enjoying the game so far! :-)
Well spotted. You are indeed correct, they are key to another ending. My hint would be, not all items/interactions are visible to the player. Some are hidden. Pay close attention to the details in scenes and press E if you think you see something. Good luck! :-)
