The difference between CSS3 and CSS2.1

the difference between CSS3 and CSS2.1
As we all know, the CSS3 we are accustomed to call the CSS2.1 has many modifications and additions. Aside from browser compatibility issues, it's easy to learn and review all the changes in one form. There is no guarantee that there is no omission, please add.

New properties	New value for each property added	New Selector	Other new features
Animation (and eight associated longhand properties) Background-clip Background-origin Background-size Border-radius (and four associated longhand properties) Border-image (and six associated longhand properties) Box-decoration-break Box-shadow Box-sizing Columns (and thirteen associated multi-column properties) Clear-after Flex (and eleven associated Flexbox properties) Font-stretch Font-size-adjust Font-synthesis Font-kerning Font-variant-caps Hanging-punctuation Hyphens Icon Image-resolution Image-orientation Line-break Object-fit Object-position Opacity Outline-offset Overflow-wrap/word-wrap Backface-visibility Perspective Perspective-origin Pointer-events (for HTML) Resize Tab-size Text-align-last Text-decoration-line Text-decoration-skip Text-decoration-position Text-decoration-style Text-emphasis (and three associated properties) Text-justify Text-orientation Text-overflow Transform Transform-style Text-shadow Transition (and four associated longhand properties) Word-break Word-spacing Writing-mode	Value "Local" for the Background-attachment property Value "Rgba ()" for accepts a color value Value "HSL ()" For the property of that accepts a color value Value "Hsla ()" For any property that accepts a color value Value "CurrentColor" for any property, that accepts a color value Value "inset ()" For the clip property Value "Linear-gradient ()" For any property that accepts an image value Value "Radial-gradient ()" For any property that accepts an image value Value "Repeating-linear-gradient ()" For any property that accepts an image value Value "Repeating-radial-gradient ()" For any property that accepts an image value Value "image ()" For the property of that accepts an image value Multiple comma-separated images for any property that accepts an image value Multiple comma-separated background-related values to match multiple background image declarations Value "Center" for the position property Value "page" for the Position property Value "Space" for the Background-repeat property Value "Round" for the Background-repeat property New values for the cursor property Values "Flex" and "Inline-flex" for the display property Values "All-small-caps", "Petite-caps", "All-petite-caps", "Titling-caps", and "Unicase" for the Font-variant property Multiple, space-separated values for the Letter-spacing property New values for the Text-align property, including "<string>", "Match-parent", "Start", "End", and "Start End" Text-decoration is now a shorthand property Keywords "Hanging" and "Each-line" declared along with length or percentage values for the Tfext-indent property Value "Full-width" for the Text-transform property REM Units for Lengths Calc () units for lengths Toggle () Units Angle units (deg, Grad, Rad, turn) Time units (s, MS)	Substring matching attribute selectors ([Att^=val], [Att$=val], [Att*=val]) : Target Pseudo-class New pseudo-classes:: Enabled,:d isabled,: checked, and:indeterminate : Root Pseudo-class New expression-based Structural pseudo-classes:: Nth-child (),: Nth-last-child (),: Nth-of-type (),: Nth-last-of-type () Other new structural pseudo-classes:: Last-child,: First-of-type,: Last-of-type,: Only-child,: Only-of-type,: Empty The negation Pseudo-class:not () Four pseudo-elements with Double-colon syntax (:: First-line,:: First-letter,::before,:: After) The Following-sibling combinator (P ~ img) :: Selection Pseudo-class (removed from the spec, but everyone uses it)	@font-face Media Queries Keyframe Animations using @keyframes Conditional Styles using @supports Namespacing using @namespace Regions Filters Note: Features that are still in flux 　　 Counter Styles Level 3 Device adaptation Display Module Level 3 Line Grid Mobile Text Size Adjustment CSS Variables Box Alignment The ' All ' property Exclusions and Shapes Generated Content for Paged Media Grid Layout Grid Template Layout Line Layout Module New features in Lists and Counters Overflow Module New features in Paged Media New features in CSS Sizing Media Queries Level 4 Selectors Level 4 CH units Viewport relative Lengths New resolution Units Compositing and Blending New features in CSS speech The Unicode-range descriptor for @font-face New features in CSS Images and replaced Content CSS Masking

CSS3 module editing The CSS3 is split into "modules". The old specification has been split into small chunks, and new ones have been added. Some of the most important CSS3 modules are as follows:

• Selector Selector
• Box model
• Backgrounds and Borders
• Text effects
• 2d/3d Conversion
• Animation
• Multi-column Layouts
• User interface

The difference between CSS3 and CSS2.1