MINI-GAMES

I loved the Beyd's training on BoF3, it's really time consuming but really satisfying when you get the results.

Some mini-games / puzzles I've made include...
-The standard rock-rolling puzzle
-An Euler walk (To complete it, you much step on every spot of the path exactly once)
-A soccer game
-A trail puzzle (Like in Narshe in FF6. You see an object walk a certain path, and you have to walk the path identically)
-A memory game that's combined with a projectile-dodging aspect that adds difficulty to remembering details correctly.
-The on-off button puzzle where whenever you depress a button, it also toggles every button adjacent to it. The object being to set them all to the off / down position (like in Super Mario RPG)

An idea that occurred to me just now is you could have a volleyball minigame. Perhaps whenever the opposing team hits the ball, it goes up high in the air where you can't see it, random numbers are generated, and then a little shadow appears where it's going to land, then the shadow gets bigger, and bigger, and then the ball lands, and if you're under it, then you hit it back up. So you're effectively chasing a shadow repeatedly. If you want, you can modify it so that the littlest shadow appears two spaces short of where the balls going to land, then the medium shadow is one space above where the ball will land, then the largest shadow is where the ball eventually lands. The direction you're facing when you hit the ball could give you some control over where you hit the ball to (i.e. which quadrant of their court you hit the ball to), and use of the enter and escape keys could give you some additional form of control (i.e. timing a key press correctly could increase your accuracy of the ball landing in-bounds; enter could be a short-range hit that's ideal when closer to the net, and escape could be a more long-range hit that's ideal when you're further away from the net).

A less fun sub-game idea I had involved some sort of stock market system. I don't remember most of the details I had in mind, but one way of implementing it could be to invest your spare currency in commodities with a currently low market price and sell them later in the game when its price is at a peak. You could potentially make it so that certain commodities are generally cheaper or more expensive when bought in one city than another. You could make a feature where the more you horde a commodity and/or use-up it's supply (i.e. if you drink 1,000 potions), the supply goes down so the price goes up (which would make the late game interesting as the price of items would increase the more you abuse them). You could also make it so that certain in-game actions affect the supply of a commodity (i.e. you raid a diamond mine, it caves-in or something in the process, the supply of diamonds goes down and the price goes up).