To add visual feedback to the cursor to show when the cursor is clicking or fusing, we can use the animation system. When the cursor intersects the entity, it will emit an event, and the animation system will pick up event with the begin attribute:
<a-entity cursor="fuse: true; fuseTimeout: 500"
position="0 0 -1"
geometry="primitive: ring"
material="color: black; shader: flat">
<a-animation begin="click" easing="ease-in" attribute="scale"
fill="backwards" from="0.1 0.1 0.1" to="1 1 1"></a-animation>
<a-animation begin="cursor-fusing" easing="ease-in" attribute="scale"
fill="forwards" from="1 1 1" to="0.1 0.1 0.1"></a-animation>
</a-entity>