Here is a list of all topics with brief descriptions:

ECS Systems	Systems are the core of the ECS architecture
CSS Tokens	Raw CSS tokens, which are created as a first step when parsing a CSS string
"auto" on rx/ry	The rx and ry properties of "<rect>" and "<ellipse>" can be set to the "auto", which means that the value of the other property is used
"<feGaussianBlur>"	Defines a filter primitive that performs a gaussian blur on the input image
"<filter>"	Defines filter effects which can be applied to graphical elements
"<image>"	Embeds an image into the SVG document
"<style>"	Defines a CSS stylesheet for the document