Anyone else besides myself know how to draw the font but not how to add OpenType features to it properly? I want to add contextual alternates so that if the word ATOM appears the regular M is replaced with an alternate M (basically the same glyph but mirrored). Should be easy, right? For some reason my font doesn’t want to cooperate.

In theory, the following should work:

feature calt {
	sub A T O M' by M.alt;
}

And yet, it doesn’t change in Photoshop. What gives??