WASD + mouse (W: forward, A: left, D: right, S: backwards). E: interact. Q: throw.
Keys open doors. Nothing special.
Doors sometimes need keys. Nothing special.
You need all three cats for the good ending. They can be found on a bookshelf, on the right side of a door and the table maze.
There's six endings (bad ending, normal ending, good ending, secret ending, fall ending and hallway ending). You get a star from every ending. To get a star (found in main menu), you need to complete the game.
After you get the first three endings (bad, normal, good) (the red stars in the main menu), you can go to the screri party.
In the middle of lots of cat food boxes in the corner of a room, there's a golden toilet. Above the toilet on the roof there's a button. When you interact with it, you get in the secret boss fight.