Just received today and assembled in less than 1 hour.  The directions, as others have noted, are a little challenging to follow but you don’t need an engineering degree.   My recommendation is remove contents from the box.  Label all the parts by number as indicated in instruction sheet and then begin assembly based on the number.  I have larger sized cats. And this seems sturdy enough to accommodate them.   Here is my 17lb cat testing out the second tier.   So far I’m satisfied but let’s see in a month.