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Fix inaccurate wording about cubic-bezier validity #42613

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Fix inaccurate wording about cubic-bezier validity #42613

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3 changes: 2 additions & 1 deletion files/en-us/web/css/reference/values/easing-function/cubic-bezier/index.md
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Expand Up @@ -41,7 +41,8 @@ A cubic Bézier curve is defined by four points: P0, P1, P2, and P3. The points

![Graph of Input progress to Output progress showing an S-shaped line curving from the origin to (1, 1) with the Bezier control points P1(0.1, 0.6) and P2(0.7, 0.2).](cubic-bezier.svg)

Not all cubic Bézier curves are suitable as easing functions because not all are [mathematical functions](https://en.wikipedia.org/wiki/Function_%28mathematics%29); i.e., curves that for a given x-axis coordinate have zero or one value. With P0 and P3 fixed as defined by CSS, a cubic Bézier curve is a function, and is therefore valid, if and only if the x-axis coordinates of P1 and P2 are both in the `[0, 1]` range.
Not all cubic Bézier curves are suitable as easing functions because not all are [mathematical functions](https://en.wikipedia.org/wiki/Function_%28mathematics%29); i.e., curves that for a given x-axis coordinate have zero or one value. With P0 and P3 fixed as defined by CSS, a cubic Bézier curve is a function, and is therefore generally valid when the x-axis coordinates of P1 and P2 are both in the [0, 1] range.


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[mdn-linter] reported by reviewdog 🐶

Suggested change

Cubic Bézier curves with the P1 or P2 ordinate outside the `[0, 1]` range can cause the value to go farther than the final state and then return. In animations, this creates a kind of "bouncing" effect.

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