// returns true when we get destroyed
public void TakeDamage(int damage)
{
health -= damage;
float t = (float)health / startHealth;
matrix.m11 = depth * t + Random.Range(0f, .1f);
matrix.m13 = matrix.m11 * .5f;
Farm.rockMatrices[batchNumber][batchIndex] = matrix;
if (health <= 0)
{
Farm.DeleteRock(this);
}
}