A radius is the distance from the center of a circle to any point on its circumference. A unit circle has radius 1 and is centered at (0, 0). section 9.1.1
For a circle centered at (centerX, centerY), the radius determines how far a point sits from the center. With angle measured in radians, calculate its position as x = centerX + r * cos(angle) and y = centerY + r * sin(angle). section 9.6
Changing the radius changes the path without changing the circle’s center:
- Increase r to move the point farther from the center. section 9.1.1
Animating an element around a center
Update the angle on each animation frame, calculate x and y from the radius, and apply the result with a CSS translate transform. A larger radius produces a wider orbit. section 9.6
