[css-animations-2] Add non-normative accessibility considerations for animations

css-animations-2/Overview.bs

@@ -1448,15 +1448,69 @@ console.log(anim.playState); // Should be 'running'.
 
 </div>
 
-<h2 id="priv">
-  Privacy Considerations</h2>
+<h2 id="privacy">
+Privacy Considerations</h2>
 
-  No privacy concerns have been reported on this specification.
+<em>This section is not normative.</em>
 
-  <h2 id="sec">
-  Security Considerations</h2>
+As for security, the privacy considerations of this specification are limited
+because it does not allow Web content to do things that it could not do before.
 
-  No security concerns have been reported on this specification.
+This specification may provide additional mechanisms that help to determine
+characteristics of the user's hardware or software.
+However, ability to determine performance characteristics of the user's
+hardware or software is common to many Web technologies,
+and this specification does not introduce new capabilities.
+
+As described in [[#accessibility]],
+implementations may provide mitigations to help users with disabilities.
+These mitigations are likely to be detectable by Web content,
+which means that users who would benefit from these mitigations
+may face a tradeoff between keeping their disability private from
+the Web content or benefiting from the mitigation.
+
+<h2 id="sec">
+Security Considerations</h2>
+
+No security concerns have been reported on this specification.
+
+<h2 id="accessibility">
+Accessibility Considerations</h2>
+
+<em>This section is not normative.</em>
+
+<h3 id="accessibility-motion">
+Motion</h3>
+
+This specification provides declarative mechanisms for animations
+that previously needed to be done using script.
+Providing a declarative mechanism has multiple effects:
+it makes such animations easier to make and thus likely to be more common,
+but it also makes it easier for user agents to modify those animations
+if such modifications are needed to meet a user's accessibility needs.
+
+Authors are strongly encouraged to use the '@media/prefers-reduced-motion' media query to provide alternative
+reduced motion or instant animations when the user has indicated a preference to ''@media/prefers-reduced-motion/reduce'' motion.
+
+Users who are sensitive to movement,
+or who require additional time to read or understand content,
+may benefit from user agent features that allow
+animations to be disabled or slowed down.
+(But see [[#privacy]] for information on the privacy implications
+of such mitigations.)
+
+User agent implementors should be aware that Web content
+may depend on the firing of <a href="#events">animation events</a>,
+so implementations of such mitigations may wish to fire animation events
+even if the animations were not run as continuous animations.
+However, it is probably poor practice for Web content to depend on
+such events to function correctly.
+
+<h3 id="accessibility-cascade">
+Cascade</h3>
+
+The cascade also allows users to disable animations entirely
+by overriding the animation properties.
 
 <h2 id="changes">Changes</h2>