Update README.md

README.md

@@ -1,35 +1,38 @@
 # Corrected fork of apca-introduction, with comments
-User xi (Tobias Bengfort) created an unauthorized repo called "apca-introduction" which unfortunately is misleading to say the least. This fork is intended to clarify, make corrections, and set the record straight.
+User xi _(Tobias Bengfort)_ created an unauthorized repo called _"apca-introduction"_ which unfortunately is misleading to say the least. This fork is intended to clarify, make corrections, and set the record straight.
 
-In addition to the corrected ***"The missing introduction to APCA"*** below, this repo also has:
+The corrected ***"The missing introduction to APCA"*** below was revised for accuracy only, with the intention of maintaining xi's original tone and simplicity. In addition, this repo also has:
 
-[Derailed analysis of APCA](https://github.com/Myndex/apca-introduction/blob/main/analysis.md) a rebuttle to xi's _"Detailed analysis of APCA"_ which mischaracterizes the differences between various contrast measures.
+[Derailed analysis of APCA](https://github.com/Myndex/apca-introduction/blob/main/analysis.md) a rebuttal to xi's _"Detailed analysis of APCA"_ which mischaracterizes the differences between various contrast measures.
 
-[Math, Lies, and Videotape](https://github.com/Myndex/apca-introduction/blob/main/Math_Lies_and_Video.md) Or put another way, _"How to use math to lie"_. This is a response to a lengthy blog post xi made that is rife with errors and misconceptions, and only serves to confuse and not enlighten on the topic.
+[Math, Lies, and Videotape](https://github.com/Myndex/apca-introduction/blob/main/Math_Lies_and_Video.md) Or put another way, _"How xi uses math to lie"_. This is a response to a lengthy blog post xi made that is rife with errors and misconceptions, and only serves to confuse and not enlighten on the topic.
 
-There are also a [large number of issue posts](https://github.com/xi/apca-introduction/issues?q=is%3Aissue) objecting to the misleading information presented at xi's repo. xi has closed many of them without action, so if reviewing, it is important to look at the closed issues. Topias has attempted to foster his miss information to other repos and other vision scientists who have summarily shut him down.
+There are also a large number of issues posted at xi's repo, objecting to the misleading information. Tobias has closed many of them without action, so if reviewing, include the closed issues. Tobias has attempted to foster misinformation to other repos and to other vision scientists, who have summarily shut him down. His motivation is unclear, however some links he uses appear to tie him to a certain group of cognitively-dissonant obstructionists.
 
 ## *In a nutshell:*
-To be sure, vision science is a dense, complicated, and abstract subject that is difficult to understand. And the misunderstandings presented by Topias potentially have a very negative effect toward fostering the continued misunderstandings and myths surrounding vision and contrast that exist today, particularly within the accessibility community. 
+To be sure, vision science is a dense, complicated, and abstract subject that is difficult to understand. And the misunderstandings presented by xi/Tobias potentially have a very negative effect toward fostering the continued misunderstandings and myths surrounding vision and contrast that exist today, particularly within the accessibility community. 
 
-### It is a primary goal of our research to educate and promote the truthfull understanding of the important characteristics of vision as they apply to readability and accessibility for all humankind.
+### It is a primary goal of our research to educate and promote the truthful understanding of the important characteristics of vision as they apply to readability and accessibility for all humankind.
 
 -----
 APCA began as a research project to address the serious failings of WCAG 2.x contrast, beginning with [Thread 695](https://github.com/w3c/wcag/issues/695) linked here for historical purposes.
 
-A revision/correction of xi's provacatively named _"The missing introduction to APCA"_ follows below.
+A revision/correction of xi's provocatively named _"The missing introduction to APCA"_ follows below.
 
 -----
 # The missing introduction to APCA
 (Note that the actual introduction is not missing, it is called [***Why APCA***](https://git.apcacontrast.com/documentation/WhyAPCA).)
 
+**Edit to add:** And there is a new plain language intro, intended for a general audience called ["Easy Intro to APCA"](https://git.apcacontrast.com/documentation/APCAeasyIntro)
+
+
 ## *What is APCA in three sentences:*
-It is a supra threshold visual contrast prediction model that is specifically tuned to readability on self-illuminated displays. It follows human perception, including critical aspects such as spatial frequency, meaning font weight and size. The APCA guidelines also inform various use cases, such as body text, fluent text, spot reading text, and non-text items.
+It is a supra-threshold visual contrast prediction model, that is specifically tuned to readability on self-illuminated displays. It follows human perception, including critical aspects such as spatial characteristics, meaning font weight and size or line thickness. The APCA guidelines also inform various use cases, such as body text, fluent text, sub-fluent text and spot reading text, and non-text items.
 
 ### *WCAG 2 compatibility?*
-APCA is enough of a paradigm shift that it is not backwards compatible with the old WCAG 2 contrast, and WCAG 3 is some time away from being the recommendation.
+APCA is enough of a paradigm shift that it is not directly backwards compatible with the old WCAG 2 contrast, and WCAG 3 is some time away from being the recommendation. However, this is not due as much to the APCA math per se, but that the APCA math is accurate to allow for flexible and accurate [design guidelines](https://readtech.org/ARC/).
 
-So in the meantime, there is the Bridge-PCA, which is backward compatible to WCAG 2, but using APCA technology. One of the urgent reasons Bridge-PCA is needed is the rise in popularity of *"Dark Mode."*
+APCA thresholds can certainly be set to levels that are backwards compatible, but at a loss of design flexibility. This approach is used in the [Bridge-PCA](https://bridgepca.com), which is backward compatible to WCAG 2, but using APCA technology. One of the urgent reasons Bridge-PCA is needed is the rise in popularity of *"Dark Mode."*
 
 ### *Bridge PCA for Dark Mode*
 As shown above, WCAG 2 contrast fails most with dark colors, and the results are relatively meaningless for colors for Dark Mode. APCA and Bridge PCA do very well with contrast prediction and guidance for dark mode.
@@ -38,12 +41,12 @@ As shown above, WCAG 2 contrast fails most with dark colors, and the result
 **And a [more in depth](https://git.myndex.com) link catalog.**
 
 
-The [Accessible Perceptual Contrast Algorithm (APCA)](https://git.apcacontrast.com/)
+The [Accessible Perceptual Contrast Algorithm (APCA)](https://apcacontrast.com/)
 is a new algorithm to predict the perceived lightness contrast between two adjacent colors. It was developed to address some issues in earlier algorithms, especially for dark colors, or when the text is lighter than the background.
 
-APCA was created by Andrew Somers at Myndex Research, and under the oversight of the Visual Contrast subgroup of Silver, and is the candidate method for contrast for [WCAG 3](https://www.w3.org/TR/wcag-3.0/) (W3C Accessibility Guidelines).
+APCA was created by Andrew Somers at Myndex Research, and under the oversight of the Visual Contrast subgroup of Silver, and is the candidate method for contrast for WCAG 3 (W3C Accessibility Guidelines).
 
-The official interactive demo is available at [www.myndex.com/APCA/](https://www.myndex.com/APCA/). No other link is canonical nor officially approved.
+The official interactive demo is available at [apcacontrast.com/](https://apcacontrast.com/). No other link is canonical nor officially approved.
 
 ## Algorithm
 
@@ -95,19 +98,31 @@ function contrastAPCA(tx, bg) {
 
 ## Migrating from WCAG 2.x
 
+**Output Values**
 - WCAG 2.x produces a ratio between 1:1 and 21:1. APCA produces a value roughly between -108 to 0 for light text (on a dark background), and 0 to 106 for dark text.
-- Unlike WCAG 2.x, APCA reports different values when you switch text color and background color.
-- The result of APCA is negative for light text on dark background. You will usually work with the absolute value though.
-- WCAG 2.x defined three thresholds: 3:1, 4.5:1, and 7:1. These *roughly* correspond to 45, 60, and 75 in APCA.
-- Compared to WCAG 2.x, APCA reports drastically lower contrast for darker colors. It also reports slightly higher contrast for lighter colors.
+ - Unlike WCAG 2.x, APCA reports different values when you switch text color and background color (polarity sensitivity).
+ - The result of APCA is negative for light text on dark background. You will usually work with the absolute value though, except for maximum contrast which is presently set at Lc -90.
+**Thresholds**
+- WCAG 2.x defined three thresholds: 3:1, 4.5:1, and 7:1.
+ - These *roughly* correspond to Lc45, Lc60, and Lc75 as functionally equivalent, but not backwards compatible. 
+ - The backwards compatible levels are APCA Lc58, Lc72, Lc85, provided the lightest color is sent to the "background" input of APCA. (i.e. disregard polarity just as WCAG 2 does).
+- APCA Bronze Level Defines six thresholds from Lc15, Lc30, Lc45, Lc60, Lc75, and Lc90
+ - Lc15: Invisibility point for some individuals.
+ - Lc30: Minimum for any sub-fluent or spot text of any use case.
+ - Lc45: Large (>36px) fluent text, or subfluent text minimum.
+ - Lc60: Medium (>24px) fluent text
+ - Lc75: Minimum for body text (>18px)
+ - Lc90: Preferred for body text
+**Practical Application**
+- Compared to WCAG 2.x, APCA reports drastically lower contrast for darker colors. It also reports slightly higher contrast for lighter colors. This is in accordance with human perception.
 - Unlike WCAG 2.x, APCA divides needed contrast into use case categories.
- - In some use cases, such as for columns of body text, APCA is stricter
+ - In some use cases, such as for columns of body text, APCA is stricter.
  - APCA is more flexible though, by handling for "derated" use cases. For instance, non-content text like a copyright bug are permitted lower contrast (prevents distraction).
 
 Also see [APCA In A Nutshell](https://git.apcacontrast.com/documentation/APCA_in_a_Nutshell).
 
 ## Comparative Examples
-These examples are based on xi's example script. The script and method was deeply flawed, and has been corrected. These examples below are intended to maintain the same comparative intent, but using useful and correct math.
+These examples are _based_ on xi's example script. The original script and method was deeply flawed, and has been corrected. These examples below are intended to maintain the same comparative intent as xi claims to have intended, but using useful and correct math.
 [![Visual comparison of WCAG 2.x and APCA](examples/screenshot1.png)](https://myndex.github.io/apca-introduction/examples/)
 [![Visual comparison of WCAG 2.x and APCA](examples/screenshot2.png)](https://myndex.github.io/apca-introduction/examples/)
 [![Visual comparison of WCAG 2.x and APCA](examples/screenshot3.png)](https://myndex.github.io/apca-introduction/examples/)
@@ -119,23 +134,23 @@ This comparison uses achromatic grays as those define readability, making the co
 
 ## Status
 
-WCAG 2 is a guideline developed and recommended by the W3.org. While WCAG 2 is not legally binding itself, it has become a normative part of some regulations in some specific jurisdictions around the globe. The fact that there is a need to define contra specifications for legal reasons makes it all the more important that there be a perceptually accurate contrast method to do so. This need led to the Genesis of the APCA.
+WCAG 2 is a guideline developed and recommended by the W3.org. While WCAG 2 is not legally binding itself, it has become a normative part of some regulations in some specific jurisdictions around the globe. The fact that there is a need to define contrast specifications for legal reasons makes it all the more important that there be a perceptually accurate contrast method to do so. This need led to the Genesis of the APCA.
 
 Currently both APCA and the future WCAG 3.0 are in active development. At the time of this writing, neither is officially recommended by the W3C.
 
 APCA is also being developed independently for other standards and guidelines beyond web content, and is rapidly being adopted by software developers and content designers.
 
 ## Evaluating APCA
 
-Evaluating a contrast algorithm is fairly straight forward as far as determining perceptual uniformity, or in other words, efficacy in terms of the predicted, relative amount of contrast across the visual range. This is because all sighted users have similarly *shaped* contrast sensitivity curves when it comes to achromatic luminance (literally, the colorless, black to white range of lightness). 
+Evaluating a contrast algorithm is fairly straight forward as far as determining perceptual uniformity, or in other words, efficacy in terms of the predicted, relative amount of contrast across the visual range. This is because all sighted users have *similarly shaped* contrast sensitivity curves when it comes to achromatic luminance (literally, the colorless, black to white range of lightness). 
 
 Luminance is the measure of light coming from the display, and perceived lightness is how a human judges the lightness or brightness, in the context of the surrounding environment. Luminance is processed by the human vision system in a manner that makes it critical for readability.
 
 On the other hand, the *thresholds* chosen for guidelines—i.e., how much contrast does a given element need—is more complicated. **_All sighted users have substantial contrast needs for best readability._** Some users have impairments that cause a reduced contrast sensitivity, and those users may need higher contrasts in general. 
 
-Note: there are some claims that some users may be over-sensitive to very high contrasts, and they then need lower contrasts in some situations such as with large bold elements. Examining this aspect of contrast perception, we find it is more related to excessively high luminance relative to a particular adaptation state. In otherwords it's not contrast per se, but an excessive luminance range, or a luminous intensity that causes significant glare and related issues. Unfortunately, this idea has been misinterpreted, resulting in poor contrast across the web. Article: [_"Please Stop Using Gray Text"_](https://tangledweb.xyz/please-stop-using-grey-text-3d3e71acfca8)
+Note: there are some claims that some users may be over-sensitive to very high contrasts, and they then need lower contrasts in some situations such as with large bold elements. Examining this aspect of contrast perception, we find it is more related to excessively high luminance relative to a particular adaptation state. In other words it's not contrast per se, but an excessive luminance peak value, or a luminous intensity that causes significant glare and related issues. Unfortunately, this idea has been misinterpreted, resulting in poor contrast across the web. Article: [_"Please Stop Using Gray Text"_](https://tangledweb.xyz/please-stop-using-grey-text-3d3e71acfca8)
 
 ## More
 
-For a deeper dive, start with [_"Why APCA"_](https://git.apcacontrast.com/documentation/WhyAPCA) and the documentation [_README_](https://git.apcacontrast.com/documentation/README) and the more in depth [link catalog](https://git.myndex.com) of related resources.
+For a deeper dive, start with ["Easy Intro to APCA"](https://git.apcacontrast.com/documentation/APCAeasyIntro) and the  [short linktree](https://linktr.ee/Myndex) and the more in depth [link catalog](https://git.myndex.com) of related resources.