I also have this project http://githistory.xyz/, I want to make a new version of it specific for tutorials, using commit messages or git notes to display a better description of each step.
You’d do better specifying a font-size and line-height, defining height in ems, or both.
(Source: the “try it” link on that page, https://githistory.xyz/babel/babel/blob/master/packages/babe..., which should probably be replaced with something else since the file in question got moved (babel-core → babel-register) and your tool doesn’t follow renames.)