This is essentially vendored from Melina Donati's 90s-tshirt-syntax, however some things didn't sound like they were right. For example, reducing font size of comments causes columns missaligning and preferred line length basically blows up.
You may both use Atom graphical package manager and
apm for installation.
apm install https://github.com/Giuppox/retro-syntax.git
Check out also atom.io for installation.
Good catch. Let us know what about this package looks wrong to you, and we'll investigate right away.