You're correct! This was a last minute addition so only #2 was used to test different node types. If I had more time, I might be able to find symbols that better represent what they mean (or just scrap the "cryptic" style altogether).
What I don't understand so far, beside what each symbol does, is why I sometime die (screen scramble, then resets). No idea what causes this. So far, that's what's bothering me the most, because I can't learn the other icons if I keep dying.