A dynamic chart where you can put: Your app size, your build configuration and it returns how much memory is needed to make a successful build and much time it will take.
A platform to ask question to people with specifics titles (Engineering Manager, Frontend Developer), which also explains the environment/context of the question.
A CSS3 animation editor that supports keyframes drag and drop and SVG.
A React Hook called useCSSDebug() which injects html *, body * { outline: 1px solid rebeccapurple }.