I did not read the instructions, and I had a bad time with the first mini game. There’s no way to know what the + and - mean without it.
I liked the game a good deal, but not explaining the rules to the player was a serious oversight that made me extremely cranky with the game. And there’s a lesson there, because lots of things that you’re otherwise willing to overlook (like its thin story) suddenly get magnified when you’re angry at a game.
I encourage everyone to do what you did and look at the directions in the walkthrough first.