http://regexr.com

RegExr is an online tool to learn, build, & testRegular Expressions (RegEx / RegExp).

https://robots.thoughtbot.com/transitions-and-transforms

https://robots.thoughtbot.com/transitions-and-transforms

https://www.cleancss.com/html-beautify/

https://www.cleancss.com/html-beautify/

http://www.cssmatic.com/box-shadow

http://netpresent.net/css-inverter.php

CSS Color Inverter

Invert all numbered colors in a CSS stylesheet

http://netpresent.net/css-inverter.php

http://lamb.cc/typograph/

CSS Typography generator

http://lamb.cc/typograph/

https://www.gridlover.net/try

Gridlover-css vertical rhythm