diff --git a/7-animation/2-css-animations/article.md b/7-animation/2-css-animations/article.md
index b2ef821f..e320520a 100644
--- a/7-animation/2-css-animations/article.md
+++ b/7-animation/2-css-animations/article.md
@@ -86,7 +86,11 @@ In `transition-duration` we can specify how long the animation should take. The
 
 In `transition-delay` we can specify the delay *before* the animation. For instance, if `transition-delay` is `1s` and `transition-duration` is `2s`, then the animation starts 1 second after the property change and the total duration will be 2 seconds.
 
-Negative values are also possible. Then the animation starts from the middle. For instance, if `transition-duration` is `2s`, and the delay is `-1s`, then the animation takes 1 second and starts from the halfway point.
+Negative values are also possible. Then the animation is shown immediately, but the starting point of the animation will be after given value (time). For example, if `transition-delay` is `-1s` and `transition-duration` is `2s`, then animation starts from the halfway point and total duration will be 1 second. You can think it like this:
+
+    `transition-delay + transition-duration = animation duration`
+
+So, if for instance, `transition-delay` is `-2s` and `transition-duration` is `2s`, then it will be as if there was no transitioning animation for that property and the changes are shown instantly. Therefore, "animation duration" must always be greater than `0s` for any animation to be shown.
 
 Here the animation shifts numbers from `0` to `9` using CSS `translate` property: