Here is the complete list of tools I use when I design in the browser using css and html.

Tachyons

I try to write as little css as possible at this point. Tachyons is normally my base for putting something together. It handles most of what I need, is easy for me to extend and weighs less than 11kb.

Postcss

For processing and manipulating CSS files.

I use the following modules:

• autoprefixer
• postcss-conditionals
• postcss-custom-media
• postcss-custom-properties
• postcss-import

Browser-sync

For auto-updating the browser after changing code.

NPM/Node

For managing build flow and dependencies.

A Web Browser

For visual testing my css is working. I normally test on lynx, safari, chrome, and firefox.

Vim

For writing HTML/CSS.

CSSSTATS

For visualizing various stats about the css I'm writing.

Pen & Paper

I still use pen & to write down notes and sketch out design ideas. When I'm building a complex component I generally write down a list of things I know about the component and a list of things I don't know for sure.