public void Update(float dt)
{
for (int i = 0; i < chTree.Decorations.Count; i++)
{
var ball = chTree.Decorations[i];
bool collide = GImage.IntersectObjectFromRectangle(Image, ball);
if (collide)
{
chTree.Decorations[i].UserObject = "dead";
}
}
Image.Step(dt);
}