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No content may flash more than 3 times per any 1-second period.

WGAC 2 criterion	2.3.1 Three Flashes or Below Threshold (A)
Category	Motion
ACT Rules

WCAG 2 criterion

2.3.1 Three Flashes or Below Threshold (Level A)

Tools and requirements

Manual Assessment

Test procedure

If there is any content on the page that flashes or strobes more than 3 times on a page (see the "Below Threshold" provision below for more details), mark a failure. There is no provision for pausable content for this criterion.

This applies primarily to multimedia content.

"Below Threshold" provision

The flashing according to WCAG 2 is permissible if the flashing is below a certain threshold, defined by a mathematical equation. For our purposes at Cornell, we simply flag any content that contains tons of flashing of any kind greater than 3 times per second a failure.

AI Prompt

Create a PHP class in the namespace "App\Services\AccessibilityAnalyzer\GuidelineRules"
that extends "App\Services\AccessibilityAnalyzer\GuidelineRuleRunner" and is called "Guideline53" that has a function with the signature "protected function findApplicableElements(Crawler $crawler): Crawler". The base class includes the function "protected function isElementIncludedInAccessibilityTree(\DOMNode $element): bool" for determining if an element is included in the accessibility tree.

Web accessibility guideline:

## No content may flash more than 3 times per any 1-second period.

### WCAG 2 criterion

2.3.1 Three Flashes or Below Threshold (Level A)

### Tools and requirements

* Manual Assessment

### Test procedure

If there is any content on the page that flashes or strobes more than 3 times on a page (see the "Below Threshold" provision below for more details), mark a **failure**.  There is no provision for pausable content for this criterion.

This applies primarily to multimedia content.  

#### "Below Threshold" provision

The flashing according to WCAG 2 is permissible if the flashing is below a certain threshold, defined by a mathematical equation.  For our purposes at Cornell, we simply flag any content that contains tons of flashing of any kind greater than 3 times per second a failure.

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