Four glasses are placed on the four corners of a square rotating table. Each glass is either upright (up) or upside-down (down). You have to turn all the glasses in same direction (either all up or all down). There are following conditions
- You are blindfolded,
- At one time you can only change two glasses (and you cannot touch other two glasses).
- The table spins after each time you change the glasses.
When all the glasses comes in one direction, then a bell rings and the game stops?