An apparatus for playing a game, the apparatus comprising a three dimensional structure assembled from a plurality of interconnectable and disengageable male and female construction elements, where each female construction element (3000, 3100, 3200, 3300, 3400, 4005, 4102, 4201, 4202, 4203, 4204, 4300, 4500, 4600, 4700) is a shaped elongate body piece with two end mating faces or surfaces (3001, 3101, 3201, 3301, 4006, 4103, 4301, 4501, 4601, 4701), each mating face having an orifice (3002, 3102, 3202, 3302, 4007, 4104, 4302, 4502, 4602, 4702) to enable each female construction element to connect to and disengage male construction elements, wherein the interconnection between two mating faces or surfaces is allowable in one orientation only, wherein each male construction element (3500, 3600, 3700, 3800, 4000, 4100, 4200, 4400) comprises two double ended pairs of male connectors (3501, 3602, 3701, 3801, 3803, 4001, 4101, 4401), the first pair of male connectors being used to connect with two complementary female orifices in two female construction elements, the second pair of male connectors being disposed through 90 degrees to the first, rotated through 180 degrees along its axis, then offset and joined with a barrel section (3502, 3603, 3704, 3802, 4004, 4101, 4406) to the first, this second pair of male connectors also being used to connect with two corresponding female orifices in two construction elements, wherein a key (3003, 3103, 3203, 3303, 4303, 4503, 4603, 4703) in each orifice is always orientated in the same way to each end, there also being a locating notch or hemispherical channel (3004, 3104, 3204, 3304, 4009, 4105, 4504) in each mating surface which widens out as it reaches the underside of each end, this channel being used to house half of the barrel section (3502, 3602, 3704, 3802, 4004, 4406) of a male construction element (3500, 3600, 3700, 3800, 4000, 4200, 4400) and enable it to flex so that other construction elements may be attached to it and alternatively, the hemispherical channels (4304, 4604, 4704) are parallel and do not widen out when construction elements are used, and wherein there are a minimum of two to four core construction elements (3000, 3100, 3200, 3300, 3400, 4005, 4102, 4201, 4202, 4203, 4300, 4700) that create Celtic knotwork or weaving patterns in a three dimensional general plane, the four being: a straight 0 degrees construction element (3000, 4005, 4102, 4201, 4300, 4700), a quadrant 90 degrees construction element (3100, 4202), a U-bend 180 degrees construction element (3200, 4203) and a loop 270 degrees construction element (3300, 3400) as viewed from above, the front or side; where each core construction element has a side profile resembling a "stretched out half a sine wave/curve" which is stretched around each top profile in the three dimensional structure, the distance the side profile of a drop being equivalent to the diameter of the female construction element, whereby each male construction element (3500, 3600, 3700, 3800) is operable to connect with up to two, three or four core construction elements (3000, 3100, 3200, 3300, 3400, 4005, 4102, 4201, 4202, 4203, 4300, 4700) and hold them together in a structure.