Is Cain's Offering Acceptable?

March on Genesis 4, we introduced the offspring by name of Adam and Eve. What happened with Cain and Abel? I mean, upon just reading the words in the text without knowing how their reference later in the New Testament,. It's not immediately clear to me why God is so mad at Cain. Why wasn't Cain's offering acceptable? Well, I think that in Cain's response to the Lord not having regard to his offering, we really see the problem.