Рух по еліпсу
float a = 8;
float b = 15;
float x = 0;
float y = 0;
float alpha = 0;
float X;
float Y;
void Update()
{
alpha += 0.005f;
X = x + a * Mathf.Cos(alpha);
Y = y + b * Mathf.Sin(alpha);
gameObject.transform.position = new Vector3(X, Y, 0);
}