Rebuilding slack.com

This post details the technical implementation of the slack.com redesign. Key contributions include: decoupling slack.com from the web client to create a streamlined codebase; introducing the 'Spacesuit' UI framework with class-based, reusable components and utility classes, resulting in a significant reduction in CSS payload (from 416kB to 132kB), unique declarations (from 1881 to 799), unique colors (from 91 to 14), and selectors (from 2328 to 1719); organizing CSS based on ITCSS philosophy and BEM-like naming conventions with single-letter prefixes for style types (e.g., `u-margin-top--small`); implementing responsive layouts using Flexbox and CSS Grid, with a shift from a traditional 12-column grid to custom Grid objects for common layout patterns and using CSS feature queries for fallback; developing Less mixins for fluid typesetting (e.g., `m-typeset`) to manage font family, size, line-height, weight, and text-transforms; implementing art direction for imagery using the `<picture>` and `<source>` elements with Picturefill polyfill for older browsers, allowing for viewport-specific image assets; and prioritizing accessibility by improving color contrast, semantic HTML, and keyboard navigation.