In Peek-a-Boo!, three children have placed sheets on their heads to pretend that they're ghosts – but unknown to them a real ghost has joined their playtime! It's up to you to determine under which sheet the real spirit is hiding as well as which color candle it's holding. To do this, players must make use of the mirrors in the castle surrounding the figures as everyone knows that true spirits don't cast a reflection...

To set up for the game, each player receives a search tile showing a symbol, and 16 candle chips (each showing one of four colors and one of four symbols) are mixed and placed facedown on the spaces on the circular track. The mechanical doohickey in the game board – which lowers mirrors out of sight when one of the ghosts is used to crank a gear in the board – is set up. You secretly place one of the four colored candles in each ghost, then set them on the game board.

On a turn, you roll the die. If you roll a number, you move a ghost of your choice the number of spaces indicated to try to land on a candle chip. If you do land on one, you reveal it, keeping the chip if it shows your symbol and leaving it faceup on the board otherwise. If you roll a ghost, you can conduct a mirror test, take a joker move, or do both. For the mirror test, you take one of the ghosts, place it in the center of the game board, then crank the gear (as each ghost has a coglike thing beneath it). If the mirrors disappear, you've found the real ghost! If not, you'll see the ghost reflected in a mirror and the angle of the mirror allows you to see the candle color; announce this color to all players. For a joker move, you move a ghost to any space of your choice to try to collect the chip on it.

Once you have all four of your chips, you immediately test a ghost of your choice to see whether the mirrors fall. If they do, you need to then name the color of candle it holds. If you fail either test, you're out of the game and play continues until the next player tests a ghost. If you succeed, you've revealed the real ghost and win!

Black Ice