Bloom version 6.0 introduces a new page styling system that we’re calling “Appearance”.

Goals of the Appearance System

Enable users to select from a set of pre-designed “Page Themes” that set things like margins, spacing, corner rounding, background colors, and page number handling
Make it easy for users to decide what fields to show on the cover (language name, topic, L2, and L3)
Shift to smaller margins and gutter by default
Simplify Bloom’s built-in stylesheets
Enable collection-wide settings that can be overridden if needed by individual books (not yet in Bloom 6.0)
Prepare the groundwork for phasing out customBookStyles.css and customBookCollections.css in the future

<aside> ℹ️ Over time, we intend to gradually deprecate the use of custom CSS in Bloom and replace it primarily with Themes + Book Settings.

</aside>
Do all of the above while keeping books backward-compatible with previous versions of Bloom (this was hard)

<aside> ℹ️ (our intent is that) Books made with Bloom 6.0 are compatible with previous versions of Bloom.

</aside>

Bloom 6.0 Appearance Features

A new “Book Settings” Dialog that lets you change some things that previously would have required custom CSS.
A set of “themes” that users can apply to their book.
An automatic conversion of some of the most common customBookStyles.css files to a corresponding theme.
A new “default” theme with the most commonly requested changes to margins and other spacing.
A “legacy 5.6” theme that retains the margins and spacing of previous Bloom versions.

Add Book Settings defaults to the Collection Settings, so that you can have all the books use the same themes and other settings
Individual books will be able to override the Collection Settings