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 Shapes & Colors Place all the sixteen pieces shown in the illustration on a 4x4 board so that none of horizontal and vertical rows, and none of two main diagonals contains two pieces of the same shape or of the same color. Play  |  Download
 The Snail Problem Suppose a snail is climbing up a slippery 30 cm wall. Each minute it climbs 5 cm, but slides back 4 cm. How many minutes will it take the snail to reach the top of the wall? Play  |  Download
 Heavy Weight by Martin Gardner There is a set of nine identical weights and simple scales (without any measures) - just as shown in the illustration. It is known that one weight is a little bit heavier than the eight others. Using only the scales can you identify the heavier weight in two weighings only? Play  |  Download
 Three Cups There are 3 cups and 3 objects - a coin, a bean and a shell. 1) To the left of the red cup is the green cup. 2) To the left of the bean is the coin. 3) To the right of the shell is the blue cup. 4) To the right of the blue cup is the bean. In which cup is the coin? Play  |  Download
 A Bag of Socks Suppose there is a bag of 3 checkered, 3 tweed and 2 white socks. Suppose you reach in without looking and pull out a sock. How many times must you reach into the bag and pull out a sock to be certain to get two socks the same color? Play  |  Download
 Stacking the Dice Puzzle Suppose seven dice are stacked as shown, and you can see all the exposed faces, including the Back view shown in the upper right corner. Find the sum of the pipe on the hidden faces of the dice. Play  |  Download
 The Jumping Coins This puzzle was described by Edouard Lucas at the end of the 19th century. Place three quarters and three pennies in a line of seven cells as shown in the Start Position above - quarters on the left, and pennies on the right. The middle cell is empty. Now interchange two groups of coins moving quarters to the right and pennies to the left (Finish Position). The middle cell has to be empty when you finish. Coins are moved just in a forward direction. This means you have to move quarters to the right and pennies to the left only. A move consists of moving a coin on the adjacent vacant cell, or jumping over an adjacent coin on the vacant cell immediately behind it. Play  |  Download
 The Number Grid Puzzle Write the numbers 1 through 8 in the circles of the grid shown in the illustration so that no two numbers inside circles joined by a line differ by 1. For example, if you put a 4 in the top circle, you cannot put a 3 or a 5 in any of the circles in the row directly below it because each of those three circles is joined to the top one by a line. Play  |  Download
 Circling Numbers Write four 1’s and three 2’s in the empty circles so that no three numbers that are beside each other on the big circle, have a sum that is divisible by three. Play  |  Download
 Sliding Pennies Six pennies are placed on the table to form the triangle shown in the Start Position. By sliding one penny at a time move them to form the shape shown in the Final Position. You can only move one penny at a time, without disturbing any other penny. When you move a penny, it has to be moved to a position where it touches two other. The pennies have to stay flat on the table at all times. Play  |  Download
 Wild Tic-Tac-Toe This game is the same as ordinary tic-tac-toe, except that at each turn the player can choose to play an X or an O. You win if you get three X’s in a row, or three O’s in a row with your turn. If the first player doesn’t make any mistakes, he or she can always win. Play  |  Download
 Four Small Triangles There are 10 equilateral triangles in the shape shown in the illustration. Remove the smallest number of matchsticks to leave four little triangles. Play  |  Download
 Easy Two Match Squares There are four small squares in the shape shown in the illustration. Remove as few matchsticks as you can to leave two squares. Play  |  Download
 Match Worm There are four small equilateral triangles in the shape shown in the illustration. Puzzle 1. Move four matchsticks and make three non-overlapping parallelograms that are exactly the same. Puzzle 2. Move three matchsticks and make two non-overlapping quadrilaterals that are exactly the same. Play  |  Download
 The Mutilated Chessboard by Martin Gardner A chessboard can be fully covered with 32 dominoes in size of two adjacent squares on the board. Suppose we cut off two corner squares of the chessboard as shown in the illustration. Now the question is if it's possible to cover entirely this new board (now consisting of just 62 squares) with the 31 dominoes? Play  |  Download
 Saddle the Horses by Sam Loyd Arrange the three cards so that each rider is in his correct riding position on top of each horse. Play  |  Download
 From Five to Four Take sixteen matchsticks and arrange them into five squares as shown in the illustration. The object is to move two matchsticks to new positions to get exactly four identical squares instead of five. Play  |  Download
 Four Knights by Paulo Guarini di Forli Exchange the black knights with the white knights as shown in Figure 1 in the minimum possible number of moves. One move is a normal knight's move on any vacant cell of the board. Play  |  Download
 Coin Triangle by Serhiy Grabarchuk Arrange nine identical coins into the right triangle shown in the illustration. Change the triangle into a square by moving the minimum of the coins. How many coins will you need to move to do this? Play  |  Download
 Broken Checkerboard Rearrange the six pieces so that to form the 5x5 checkerboard shown in the center of the illustration. Play  |  Download
 Magic Triangle 3X Place all the numbers from 1 to 6 in the circles along the sides of the triangle (one number per circle), so that three numbers on each side add up to the same total - a magic sum. There are four different magic sums that could be reached for this puzzle. All these sums are from 9-12 number range. Can you find all of them? Play  |  Download
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 Last Updated: September 10, 2009 top
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