Adjusting movement/look limits in first person mode

Hi there. In first person mode, the player can move the mouse infinitely left or right to spin the character around, but when moving the mouse up or down, the character stops when looking either straight up or straight down. Does anyone know of a way to remove those limits so that one could “do a flip” with the camera and just the mouse? Also adding a roll element would be cool. I’m working on a game with zero gravity and I want all movement to maximize disorientation. If anyone has some advice on where to look or how to address this, I’d be very grateful.