Flou is a domain-specific language (DSL) for describing flowcharts. It is also a CLI of the same name that renders the previously mentioned flowchart description into an SVG file.
Poloto graphs can be stylized using css either directly in the SVG, or from inside of html with an embedded svg. The latter allows the user to dynamically match the svg to their website's theme.
In Portal Explorer you can view how interesting portals are constructed, and visually explore their properties by moving and rotating them. This program doesn't work well on mobile, better opened from PC.