In addition to being able to animate attributes along a linear timeline, the Boxely UI Toolkit allows you to animate attributes at a set time. These animations are called "set animations" and can be used to compliment any animation you're building. The premise of a set animation is that you can set the value of an attribute at a predetermined time. For instance, if after 10 seconds (10,000 milliseconds) you want a box to change its opacity attribute to 0%, a set animation can be created to assign the value at the predetermined time, as shown here:

<library...>
  <animation id="myOpacityAnimation">
     <set name="opacity" type="style" to="0%" begin="10000ms"/>
    <animate name="opacity" type="style" dur="250ms" from="before" to="100%"/>
   </animation>
</library>

In the above example, when myOpacityAnimation is triggered, it will animate the opacity of the box to 100% over 250ms and then, at 10000ms, it will set the opacity to 0%.