Added a note about keyframes in 7-1 pattern

en/_architecture.md

@@ -70,12 +70,16 @@ Ideally, we can come up with something like this:
 
 ### Base folder
 
-The `base/` folder holds what we might call the boilerplate code for the project. In there, you might find the reset file, some typographic rules, and probably a stylesheet (that I’m used to calling `_base.scss`), defining some standard styles for commonly used HTML elements.
+The `base/` folder holds what we might call the boilerplate code for the project. In there, you might find the reset file, some typographic rules, and probably a stylesheet defining some standard styles for commonly used HTML elements (that I like to call `_base.scss`).
 
 * `_base.scss`
 * `_reset.scss`
 * `_typography.scss`
 
+<div class="note">
+  <p>If your project uses <em>a lot</em> of CSS animations, you might consider adding an <code>_animations.scss</code> file in there containing the <code>@keyframes</code> definitions of all your animations. If you only use a them sporadically, let them live along the selectors that use them.</p>
+</div>
+
 ### Layout folder
 
 The `layout/` folder contains everything that takes part in laying out the site or application. This folder could have stylesheets for the main parts of the site (header, footer, navigation, sidebar...), the grid system or even CSS styles for all the forms.