Being able to re-use an existing symbol by flipping it on its horizontal or vertical axis would be a huge help. I could avoid importing additional images and could instead “re-purpose” an existing asset, thus saving on file weight.
Is there some way to flip an item on its axis that I am missing?
Metrics > Rotation > X > 180°
Manually editing CSS styles is also an option.
More than one way to skin a cat. Thanks, Michael.
Rotations on elements are not supported in some browsers.
Yup. Figured that out. Thanks, Andrew. 
I don't think web developers are truly helping web visitors by supporting outdated web browsers. Old browsers are security risks.
Opera Mini, IE 8, IE 9?
I'm not really a Microsoft hater. I liked the good old days where ~90% of visitors used IE. That made testing simple. But today, it's looking pretty bad for IE 6, 7, 8, 9 and even 10...
Beginning January 12, 2016, only the most current version of Internet Explorer available for a supported operating system will receive technical support and security updates.
in IE9 you lose the perspective distorsions
also IE10/11 implementation is without prefixes and most importantly does not support the transform-style: preserve-3d, this mean you can't use "groups" in Hype with complex rotations.