Properties are just values
Anywhere you'd write a number, you can write a property instead. So ellipse(ball.x, ball.y, ball.size, ball.size) draws a circle exactly where the ball says it should be — and at the size the ball says it should be.
NOTE
Change one property — say size: 200 — and the drawing updates everywhere it's used. That's the payoff of keeping the data in one place.