What is an easy diy way to block off play area

Hello, thankyou for taking the time to read!
I was wondering if anybody had a diy way to block off my room so that my little Nigel can play safely without getting into things I dont want him to. I have tried this rather large and tall piece of cardboard but my curious little man just pushes out of the way. I think the reason he is able to do that is because (besides his mischievous behaviors) of the cardboard is not sturdy and has to lean on things. Please help he does not get as much...

What is an easy diy way to block off play area