title: How to assign instance variable to SKSpriteNode?
body: <p>I have several <code>SKSpriteNode</code>'s called <code>circle1</code>, <code>circle2</code>, etc. I want to track how many times each one rotates using an <code>Int count</code>. Is there any way I could assign <code>count</code> to be a member of <code>circle1</code>? Something like <code>circle1.count = 2</code>, the way you would do <code>circle1.position = ...</code>? I don't want to have to create a new variable for each circle, as there are quite a few.</p>