"Now, if you try to cross this line, you'll see that you cannot", Valerion continued, smiling. "You can try, if you want".

Still in a daze, Adrien nodded, then walked towards the circle; as expected, his foot was met by an invisible wall. "Wow", he whispered.

Valerion smiled. "Anyway, you don't always need to draw a complete circle to defend yourself; an arc is often sufficient. You will need to make quick decisions based on the entity of your threat. If you were to defend yourself from an incoming punch, drawing a full circle would cause you to waste time, energy, and potentially expose your back to the attacker; in that case, it would be far more efficient to draw an arc that would protect you from the actual range of your threat".