Fine Tuning Argument For God s existence

Hello everyone I am an atheist and yesterday I was debating a catholic about god’s existence and during the debate he brought an argument that the universe is so fine tuned that even a little change in its properties would make the universe collapse and I searched about it it’s true that if gravity is just slightly stronger than now then the universe would collapse so he said that such fine tuning of the universe must have been done by a creator because just a little change in design would make it collapse what should be the reply to such an argument ?