Pro opinion wanted: what fps is too low?

I’m making a puzzle game and at intense moments, fps goes down a bit to around 30-40. What do pro’s consider too low? Would you release a game that has 30 fps hickups? Or is that simply not good enough?

Otherwise, my game hovers at a clean 60 when user is passive (CPU is the bottle neck).

My initial standpoint was that a puzzle game (at least of the type I’m making) should never need to even hickup below 60… But I’m having these hickups and trying to decide how much of a big deal it is…

I dont think you need to worry about FPS. I would worry more about if the users notice. Most people wont recognise a drop from 40-30 FPS as our eyes cant keep up with anything above 30 (Or something like that)