reveal.js 3.0 changes the default style of the framework (demo). If you want to return to the old defaults please take a look at the migration guide.

Major updates:

• New default theme "black"
• New theme "white", same typography as "black" but inverse colors
• Default transition changed from 3D rotation to 2D sliding
• Presentations scale up to make better use of high resolution viewports
• Video backgrounds (more info)
• Iframe backgrounds (more info, #1029 by @lutangar)
• Lazy loading of image, iframe, video and audio (more info)
• Help overlay when pressing ? (#943 by @navateja)
• Slide content is now announced to screen readers (#854 by @mpnkhan)
• Rewritten PDF export layout, fixes a number of issues and adds support for vertical centering
• Markdown separator attributes renamed from data-notes and data-verticalto data-separator-notes and data-separator-vertical.

Other updates:

• Minified files (reveal.min.js and reveal.min.css) are no longer tracked in the repo
• Core stylesheet is now precompiled using Sass
• Core stylesheet is now using autoprefixer (#1007 by @burnpanck)
• Built-in postMessage API (more info)
• The .reveal element is given a "has-light-background" or "has-dark-background" class when a per-slide background color is detected
• Speaker view
  • New design
  • Now works when running a presentation from file://
  • Disabled slide transitions to improve main presentation performance
  • Disabled auto-sliding to prevent conflicts with main presentation
  • Disabled 'S' shortcut from working inside of speaker view
• New API method: getState/setState (more info)
• New API method: getProgress
• New API method: getTotalSlides (#858)
• Fragments are included in progress calculation
• highlight.js updated to 8.2, now includes all supported languages rather than a subset
• Removed transitions into and out of the overview mode
• Simplified .slides container layout, no more -50% offset on individual slide elements
• Renamed "linear" transition to "slide"
• Renamed "default" transition to "convex"
• Background images, videos and iframes are lazy loaded
• Moved content related styles out of core stylesheet into themes
• Removed Ruby dependency by switching to node-sass (#975 by @miira)
• Removed theme config option (#1061)
• Included version of League Gothic is no longer subset (#989)
• UMD support (#869 by @ahdinosaur)
• Refreshed content in default presentation

Bug fixes:

• Invisible fragments no longer catch mouse events (#845)
• Prevent named links with non-latin characters from skipping to presentation end (#836)
• data-autoplay attribute now works on the first slide
• Auto-sliding now works for fragments on last slide (#974)
• Fix issues with RTL navigation
• Fix edge cases where isFirstSlide incorrectly returned true
• Fix issue with automatically playing/pausing YouTube and Vimeo embeds
• Fix double-navigation on touch for some Android devices
• Fix calculation of fragment index when multiple fragments have the same index
• Many more...