I'm creating a relatively complex nav layout for a single-page scrolling site using GSAP and ScrollMagic. The "upcoming" page in the navigation tweens upward as you scroll down until it hits the top of the nav, and then a page transition is triggered (which is unrelated to this issue). I've included a stripped-down Codepen with only the Nav - please view it in Full View using Chrome or Firefox to see the effect working properly.
The value it's tweening to achieve that effect is relatively complicated - it's top: calc(-100vh + [nav container height] + [2x nav bottom property]) which has the