[cavy-cool-crazy]

OK.

To make the door you use cable/zip ties. Pull them so that they pull the grids almost together, but not quite. Leave all the other sides, so that just one side of the grid is attached, and you have a swinging door. If you want to make a door which is one complete one for 2 levels, then you simply attach a door above the lower level door, and tie the bottom one to the top one. If that makes sense!

To make a second storey, just imagine building a separate cage on top of the first level, but leave one grid out in the side so that you can have a ramp leading from floor 1 to floor 2.