📝 Improve comments

docs/how-to-create-new-effects.md

@@ -150,13 +150,15 @@ var SimpleFade = class SimpleFade {
     return new Shader(settings);
   }
 
-  // This is also called from extension.js. It is used to tweak a window's open / close
+  // The tweakTransition() is called from extension.js to tweak a window's open / close
   // transitions - usually windows are faded in / out and scaled up / down by GNOME Shell.
   // The parameter 'forOpening' is set to true if this is called for a window-open
   // transition, for a window-close transition it is set to false. The modes can be set to
   // any value from here: https://gjs-docs.gnome.org/clutter8~8_api/clutter.animationmode.
-  // This also determines how the uProgress uniform value will progress in the shader.
+  // The only required property is 'opacity', even if it transitions from 1.0 to 1.0. The
+  // current value of the opacity transition is passed as uProgress to the shader.
   // Tweaking the actor's scale during the transition only works properly for GNOME 3.38+.
+
   // For this effect, windows should neither be scaled nor faded.
   static tweakTransition(actor, settings, forOpening) {
     return {