I spent most of the time working on the art, so I unfortunately didn’t have a lot of time to add secrets or additional puzzles.
You can use the cat food on the top floor to feed the cat after which some heart particles will appear (you only need one cat food for that, the other is useless).
Also it is intentional that you can’t open the doors while the elevator moving, but there is a bug which allows you to do that regardless. Basically you close the doors and select a floor, and as soon as the elevator reaches that floor you select another floor. This way the elevator starts opening the doors, but also moves towards the other floor.
Thank you for playing! :D