Abel and Cain

Genesis 4:4b-5a - The LORD looked with favor on Abel and his offering, but on Cain and his offering he did not look with favor.

How did Abel and Cain know what the LORD thought of their offerings? The previous verse says they brought the offerings to the LORD. Might they have done this literally? Was the LORD visible to them often enough that they knew where to go and see him -- they knew where he lived, so to speak? If so, perhaps the phrase "the LORD looked" can be taken literally too. Maybe they were all standing next to each other and God had a smile on his face after seeing Abel's offering but had a downcast look after turning to Cain's. That certainly would explain how they knew what the LORD thought.

Did you ever wonder what Cain's real reason for killing Abel was? Was it because of the good offering/bad offering situation? Abel hadn't won a competition in which Cain took second (or last) place. What Abel did there really shouldn't have had anything to do with the murder. Cain should have only been angry with himself and perhaps (though wrongly too) with the LORD who had judged his offering and his heart. I wonder if there were other things that happened before, after, or both before and after the offering incident that led Cain to kill Abel -- similar to what led Joseph's brothers to treat thim so badly and even want to kill him.

Then again, maybe it was just the problem with the offering. People are really good at blaming anything and everything but themselves when it comes to a wrong they've done. And Cain only had to look as far as Mom and Dad for examples, didn't he?