Had some time on my hands this morning waiting for rows to import into a database.
So I grabbed three cardboard boxes, a cutter and sticky tape.
And made this:
It's crappy, but the kittens love it.
They were flaked out after a meal from mom, but I'll take photos when they are playing in it.
If you do this yourself, make the holes HUGE.
I did and had to go back and carve chunks out of the cardboard so they could fight and tussle in the openings.