When selecting the interface's shape, the table below the shape dictates the rules. All except #2 have the same things. Dashes [-] are the energy bar, Diamonds/Units [<>] are the diamond-things used to purchase upgrades, and the Crosses [x], IDK, probably something to do with defense from the lines/rays.
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).
Wordless games are really hard to do. Good luck!
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.
Also, after posting this, [x]'s are defence. If you have exclamation marks at the bottom you will get hit, otherwise, you're fine.