**Knot 221** 2000-10-05 | **A New Proof of The Four Colour Theorem** Ashay Dharwadker presents a new proof of the four color theorem that uses group theory and Steiner systems, illustrated using a map of Madhya Pradesh and adjoining states in India. |

**Knot 220** 2000-09-25 | **MATHS QUIZ 2000** As part of the World Mathematics Year, every mathematician in the world is invited to take part in a contest! |

**Knot 219** 2000-09-18 | **BitArt, Spirolateral Series** A nice collection of spirolaterals that you can see in generation. |

**Knot 218** 2000-09-07 | **Synergetics on the Web** Kirby Urner presents an artfully presented site on Synergetics, which uses geometric metaphors to connect and organize experiences. |

**Knot 217** 2000-08-16 | **Visualising functions** Hans Lundmark shows how to use "domain coloring" in order to visualise complex analytic functions. |

**Knot 216** 2000-07-26 | **Torus Games** Jeff Weeks has created challenging games, including Tic-Tac-Toe and Chess, to play on the Torus and the Klein bottle. |

**Knot 215** 2000-07-17 | **The Prime Maze** A great game by Dr. Paulsen using prime numbers. Can you make it through the maze? Check out some of his other web-based math games. |

**Knot 214** 2000-07-10 | **The Euler Project** This site makes available in English some of the works of the great mathematician Leonhard Euler. |

**Knot 213** 2000-07-04 | **Zero Saga** Everything that you **ever** wanted to know about Zero! |

**Knot 212** 2000-06-20 | **The Geometry of War** An interesting virtual exhibition from The Museum of the History of Science in Oxford on the uses of geometry in the art of warfare during the Renaissance. |