Baldurs Gate introduced me to the rules of AD&D.I'm not entirely sure why OD&D settled on these systems. Ability checks to roll under your ability score, ok, that makes sense. But there's so much else that can trip up newbies, lol.
DM: "Ok, so, your AC goes down, based on what armor you wear, and your defensive adjustment from Dexterity lowers your AC."
Player: "Right, ok, so in that case, my Platemail gives me 3, my 15 Dex reduces that to 2 and my shield...oh!"
Player: "So that magic shield +2 is cursed then! I want to get rid of it!"
DM: "No, it's not cursed, it lowers your AC by 2."
Player: "Wouldn't that be a Shield -2 then?"
So I load up the game and make a fighter and start off next to the inn.
I go in and buy some leather armor and equip it…. Why did my Armor Class go down? I figured I wasn’t trained to use it yet and took it off and went about my way to explore..