Overall the mattress is pretty firm which is what we like. There is a little sponginess to it when you begin to relax and fall asleep. Nice bed for the price. Hopefully it lasts 7-8 years like my last mattress. 
Oh if you really want to have fun. Video your kids or a friends kids jump onto the bed. Don’t tell them it’s firm and watch them bounce off it like a bouncy ball. Lol.