By default, only one avatar is available. Here’s how to unlock the others:

 

1- Go to the “Quiz” section:

 

 

2- Select your apparatus/groups/values and start the quiz:

 

 

3- Guess the group and value of the elements shown:

                

 

4- If you score 100%, your avatars will be unlocked!

 

5- All avatars are now available. Select one, and it will be applied to all animations!