This video shows a simple door i made to seamlessly enter a hobbit-hole. It is activated using a button from either side which powers a piston using quasi-connectivity. In order to update the piston i use 2 observers facing each other creating a clock which powers an activator-rail. The most tricky thing with this door was to get the side where you want to leave to close delayed which i achieve by giving a fast pulse to a piston that toggles the position of an obeserver, which then dependig on the position powers a piston in order to deactivate either the the inside or the outside-closing-mechansim. it is important not to use a full block at the drops becauce otherwise the suffocation-damage messes it up. A nice side-effect ist that even if you try to enter from the side that is currently not selected, you get back up and can go through the next time. I should mention that am am not a door-guy at all so I guess this door can be compacted and maybe also be made more reliable.