Ohh I figured out the biting thing, The feature is a good idea but it needs a sound effect and maybe an obvious jaw motion to really be convincing. I expected her to bare her teeth or something.
Please add the option to activate it whenever, regardless of depth. Maybe SPACE could trigger it since that would normally be used to hold her down anyway, make it where you can set space to have a chance to bite and the the chance can be put to 100% if desired. I want to take her tease to the next level and make her bite unexpectedly, even on his poor sensitive head >:) Call it femdom or masochist mode haha.
FAQ's and help here: https://www.undertow.club/forums/help.81/