One idea for a "puzzle" I implemented into a game I was working like 5 years ago but quit is to have a set of candles located somewhere, each of a different color. Somewhere in the house you find a memo or something that hints to the candles, saying the order you have to light them, but still relates in some way to the story you have set up. For example, the colors are pink, red, and yellow. The memo says, "There shall be light: Perry Y. Randell will lead the way." So that means you light the candles, first pink, then yellow, and last red, and then a door opens or something.