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I tried implementing this icon with a 19 degrees rotation:
http://fortawesome.github.io/Font-Awesome/icon/slack/

It should work, can somebody tell me why it isn't?
I tried reinstalling the assets, but I guess my frontend/symfony skills aren't that up to date

https://github.com/SweetLakePHP/SweetLakePHP/issues/64

Also, hovering on the link shows the underline somewhat weird to me.
Any suggestions?

Also, is the 19-degree angle fix in the proper .css file?