Scrolling vertically when horizontal scroll is used on a trackpad

Hey everyone,

I just built this custom menu using this T.RICKS template. Everything is great when I scroll up and down, but I would also like to be able to scroll left/right on my trackpad to achieve the same vertical scrolling effect. Is there any way in JS to assign horizontal trackbar movement to scroll vertically?

P.S: also any chance to hide scrollbar in Firefox, while still allowing to scroll? So far I was only able to hide it for Chrome and Safari.

Thanks in advance!

Here is my site Read-Only: LINK ( the menu is on the HOME page)