BACKGROUND TO THE INVENTION Many different forms of puzzle are known. One three- dimensional puzzle, known as a"Rubik's Cube" (TM) comprises a number of coloured elements which are secured to a framework. Most of the elements can slide and rotate about the framework so that they may be moved relative to one another. The complete puzzle forms a cube having six sides, each side having a number of (typically nine) elements, the elements on each side initially being similarly coloured.

The elements may be relatively shifted around the framework to mix up the coloured elements and then the user can seek to return the elements to their start positions so that each side has elements of only one colour.

Solving a"Rubik's Cube" (TM) puzzle is extremely difficult, and so it is usually necessary for the user to learn the solution from others rather than arriving at the solution for himself or herself. If the solution is not available, the puzzle may remain unsolved, in which case the elements remain mixed up and the puzzle may be discarded.

SUMMARY OF THE INVENTION The present invention provides a puzzle which can be disassembled and subsequently rearranged back to its initial configuration even if it has not been solved, the puzzle therefore being less likely to be discarded.

According to the invention there is provided a puzzle comprising a number of elements which are movable relative to each other, each element having interconnecting means by which it may be movably interconnected with other elements, the interconnecting means allowing an element to be moved translationally relative to an interconnected element in a substantially linear direction.

The elements are not secured to slide or pivot upon a framework as in a"Rubik's Cube" (TM) but instead are held together by the cooperating interconnecting means.

Preferably, the elements are substantially identical in form (i. e. in their three-dimensional structure), but are coloured to allow a pattern to appear on the outside of the puzzle, the pattern being variable depending upon the arrangement of the elements therein.

Preferably, the elements have six sides; preferably the sides are all equally-sized squares and the elements are cubic.

Preferably, each element has an interconnecting means on each of its sides. Desirably, each element has three first interconnecting means and three second interconnecting means, the first interconnecting means being arranged on three adjacent sides and the second interconnecting means being arranged on three adjacent sides, opposed sides of the element having one first interconnecting means and one second interconnecting means.

Desirably, each first interconnecting means comprises a plate mounted upon a neck, the area of the plate being larger than that of the neck, the neck and plate being located substantially centrally upon the respective surface of the element. Desirably also, each second interconnecting means comprises four ledges and four supports, the area of a ledge being greater than that of a support, each ledge being

mounted upon a support ideally adjacent a respective corner of the surface of the element. The first and second interconnecting means are arranged so that the plate carried by one element can lie underneath the ledges of an adjacent element to retain the two elements together, the neck and supports allowing relative translational (sliding) movement of the elements in two substantially perpendicular directions.

Thus, whilst it will be understood that in the assembled 3- dimensional puzzle each element may be moved (perhaps together with other elements) in any of three substantially perpendicular directions, the interconnecting means limit relative movement between interconnected adjacent elements to two substantially perpendicular directions.

Preferably the puzzle comprises nine, twenty eight, or sixty five elements, the number of elements allowing them to be arranged into a"main cube" (i. e. an arrangement having an equal number of elements along each axis), with a single additional element. The additional element is initially outside the volume of the"main cube", but can be mounted thereupon by way of its interconnecting means. The user can slide the additional element (and the line of elements within the main cube to which it is interconnected) relative to the other elements in the main cube, causing another element to be pushed out of the main cube. Said another element can then be translated around the main cube, and then slid back into the main cube and at the same time push out yet another element from the main cube.

As each element is pushed out of the main cube and subsequently translated thereacross and reintroduced to push out another element, the arrangement of elements in the puzzle changes. It is arranged that the sides of the respective elements which are initially exposed on the surface of the puzzle can be coloured, and in particular differently coloured to the unexposed sides. Rearranging

the elements causes the different colours to become mixed up. When the elements have been mixed up the puzzle can be solved if the user is able to reorganise the elements so that the coloured parts are returned to their original positions, without disassembling the puzzle.

However, since each element is slidable relative to all other elements to which it is interconnected, if desired the entire puzzle can be disassembled and reassembled so that a user who is not able to solve the puzzle can disassemble the unsolved puzzle and subsequently reassemble it into its initial state, and so can continue to enjoy the puzzle without becoming defeated by its complexity. The user can therefore undertake progressively more element movements when disorganising the puzzle before seeking to reorganise the puzzle, so as slowly to increase the difficulty of solving the puzzle.

As above indicated, it is desirable that the elements are cubic, and the puzzle is cubic, but this is not necessary.

Thus, it will be understood that the elements in the puzzle retain their relative orientation, i. e. they only slide relative to each other and do not rotate relative to each other. Accordingly, each element can be cuboid (in which two opposed sides are square and the other four sides are non-square), or irregular (in which all of the sides are non-square), if desired, and the resulting puzzle can be correspondingly shaped. It is also preferable, but not necessary, that the puzzle have an equal number of elements along each axis. Alternatively stated, even if the elements are cubic the puzzle need not be similarly cubic, and it would instead be possible for the puzzle to be made up of irregular sides (for example two opposed sides could be made up of six elements arranged in two rows of three, two other opposed sides could be made up of eight elements arranged in two rows of four, and the remaining two opposed sides made up of twelve elements arranged in three rows of four).

Notwithstanding the possible non-cubic constructions of the puzzle, the term"main cube"will be used throughout this specification to refer to the basic form of the puzzle to which the additional element can be attached, notwithstanding that the basic form could be non-cubic both by virtue of the non-cubic shape of each element, and/or because of the unequal numbers of elements along the axes.

Also, references herein to the elements being"cubic"or not refer to the basic structural shape of the element excluding the interconnecting means. In the preferred embodiments described the interconnecting elements project from the basic structural shape so that whilst the basic structural shape is cubic the overall element is not cubic.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a first persective view of a representative cube, to demonstrate the basic structure of the elements of the puzzle according to the invention; Fig. 2 shows a second perspective view of the cube of Fig. 1 Fig. 3 shows a front view of an element of the puzzle according to the invention; Fig. 4 shows a perspective view of the element of Fig. 3 from a first direction ; Fig. 5 shows a perspective view of the element of Fig. 3 from a second direction;

Fig. 6 shows a perspective view of the element of Fig. 3 from a third direction; Fig. 7 shows an assembly of eight elements of Figs. 3-6, which assembly provides the main cube of a first puzzle according to the invention ; Fig. 8. shows an assembly of twenty seven elements of Figs. 3-6, which assembly provides the main cube of a second puzzle according to the invention ; Fig. 9 shows a perspective view of the main cube of Fig. 8 together with an additional element to form the second puzzle; Fig. 10 shows a plan view of a part of the interconnecting means of the first, second and third sides of another embodiment of element; and Fig. 11 shows an exploded representation of the main cube of a third puzzle according to the invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS The representative cube 10 of Figs. 1 and 2 has six sides, all of square shape and equal size. Fig. 1 shows the first side 11, the second side 12, and the third side 13, Fig. 2 shows the fourth side 14, the fifth side 15 and the sixth side 16.

The first side 11 is opposed to the sixth side 16, the fifth side 15 is opposed to the second side 12 and the fourth side 14 is opposed to the third side 13. The arrangement of sides described for the cube 10 is shared by the elements of the puzzles described below.

The puzzle is constructed from a number of elements 20 (Figs. 3-6) which are all of substantially identical three- dimensional form. In this embodiment the elements 20 are cubic, i. e. they are each formed from a basic cube such as 10 to which interconnecting means are attached.

As shown in Figs. 3-6 each element 20 has a first interconnecting means 21 mounted upon its first side 11, its second side 12 and its third side 13, and a second interconnecting means 22 mounted upon its fourth side 14, its fifth side 15 and its sixth side 16.

The first interconnecting means 21 comprises a plate 23 mounted upon a neck 24, the area of the plate 23 being larger than that of the neck 24, the neck and plate being located substantially centrally upon each of the first side 11, second side 12 and third side 13 of the element 20. The second interconnecting means 22 comprises four ledges 25 and four supports 26, the area of a ledge 25 being greater than that of a support 26, each ledge 25 being mounted upon a support 26 adjacent a respective corner of each of the fourth side 14, fifth side 15 and sixth side 16 of the element 20.

It will be noted that in this embodiment the top outer surfaces of the ledges 25 are chamferred so as to facilitate correct alignment and engagement between the interconnecting means of respective elements as they are slid relative to one another in an assembled puzzle. To further facilitate correct alignment and engagement other edges of the element can be chamferred, for example the top inner edges of the ledges, the bottom edges of the ledges, and the top and/or bottom edges of the plates 23.

The first and second interconnecting means 21, 22 are arranged so that the projecting parts of the plate 23 carried by one element 20 can lie underneath the projecting

parts of the ledges 25 of an adjacent element so as to retain the two elements together.

The separation S between the supports 26 is greater than the width W of the plate 23, the separation s between the ledges 25 is greater than the width w of the neck 24. Also, the height H of the neck 24 and the supports 26 is slightly greater than the thickness T of the plate 23 and the ledges 25. These dimensions ensure that the cooperating interconnecting means 21, 22 allow relative translation (sliding) movement of the interconnected elements in two substantially perpendicular directions substantially parallel to the edges of the interconnected sides. Thus, another element 20 interconnected to the third side 13 of the element 20 shown in Fig. 3, and directly overlying the element 20 as drawn, will be able to slide relative to the element 20 in the directions X and Y. However, once the overlying element has been slid a small distance in the direction X relative to the element 20 it will no longer be able to slide in the direction Y, and vice versa.

Similarly, another element 20 interconnected to the first side 11 of the element 20 shown in Fig. 3 will be able to slide relative to the element 20 in the directions Y and Z (the direction Z being into and out of the paper as drawn), and another element 20 interconnected to the second side 12 of the element 20 shown in Fig. 3 will be able to slide relative to the element 20 in the directions X and Z.

Fig. 7 shows a main cube 30 for use in a puzzle according to the invention, the main cube 30 being formed as an assembly of eight substantially identical elements 20a-h (element 20g is underneath element 20c and cannot be seen in this view).

When constructing the main cube 30 all of the first sides 11, second sides 12 and so on, of each element 20a-h should be aligned, so that each side of the main cube 30 presents all first interconnecting means 21 or all second interconnecting means 22, as shown.

Considering element 20a, the exposed sides of this element are the third side 13, the fifth side 15 and the sixth side 16. The first side of the element 20a is interconnected to the sixth side of the element 20b, the second side of the element 20a is interconnected to the fifth side of the element 20e, and the fourth side of the element 20a is interconnected to the third side of the element 20d, so that these sides of element 20a are not exposed.

When so constructed, an additional element (not shown) can be mounted upon the main cube 30 by sliding it along from an edge of the main cube. Specifically, an additional element (not shown), but which is substantially of identical three- dimensional form to the elements 20a-h, and correspondingly oriented, can be slid downwardly as drawn from the edge 40 (the edge 40 being the junction of the third side 13 and the fifth side 15 of the element 20a) so that the second interconnecting means 22 of the fourth side of the additional element slides across and engages the first interconnecting means 21 of the third side 13 of the element 20a. When the additional element has been positioned correctly, it will be aligned with the elements 20a and 20d and form a continuation of that line of elements. (It will be understood that the additional element could equally well be slid into this position by starting from the edge 41 (the junction of the third side 13 and the sixth side 16 of the element 20a) and sliding it to the left as drawn).

When so positioned, the additional element can be pressed generally towards the top right corner of the paper as drawn, which will cause the line of elements comprising the additional element and the elements 20a and 20d to slide backwards relative to the remaining elements in the main cube 30, pushing element 20d out of the main cube which as rearranged comprises the additional element and elements 20a-c and 20e-h).

The projecting element 20d has therefore become the additional element attached to the main cube, and remains attached to the main cube (and so as a part of the puzzle) by means of the first interconnecting means 21 of its third side 13 engaging the second interconnecting means 22 of the fourth side 14 of the element 20a. The projecting element 20d may then be translated or slid relative to the element 20a either to the left as drawn and into engagement with the element 20c, or downardly as drawn and into engagement with the element 20h. Alternatively, element 20d may be detached from the main cube by sliding it to the right or upwards as drawn relative to element 20a, and then reattached at any position upon the main cube, as desired by the user.

Assuming that the additional element 20d is slid to the left as drawn to engage the element 20c, the element 20d will form a continuation of the line of elements 20b and 20c.

That line of elements could then be pressed (generally towards the bottom left corner of the paper as drawn) to move the elements 20c and 20b and reintroduce the element 20d into the main cube as the element 20b is pushed out of the main cube. Element 20b therefore becomes the additional element attached to the re-rearranged main cube.

It will be understood that each line of elements can be slid relative to the other elements in the puzzle, in the direction of each axis, i. e. the line of elements 20a and 20b (and all parallel lines of elements, together with the additional element if fitted) can be slid generally to the left or right as drawn, the line of elements 20a and 20d (and all parallel lines of elements, together with the additional element if fitted) can be slid generally forwards and backwards as drawn, and the line of elements 20a and 20e (and all parallel lines of elements, together with the additional element if fitted) can be slid generally upwards and downwards as drawn.

When the puzzle is initially constructed the exposed sides are marked (for example coloured) differently from the unexposed sides. The exposed sides can all be similarly marked if desired since in puzzles having twenty eight or fewer elements each element can only occupy one position in the correctly assembled puzzle. Thus, if for example the puzzle comprises nine elements, for example the eight elements 20a-h shown in Fig. 7 and an additional identical element, the initially exposed sides can all be coloured white and the unexposed sides all coloured black. All sides of the additional element can be coloured gold, for example (or any colour other than black or white). Despite all exposed sides in the main cube 30 bearing the same colour, to solve the puzzle the element 20a must occupy the position shown in Fig. 7 since it is the only element having its third side 13, fifth side 15 and sixth side 16 coloured white, any other element 20b-h which occupies that position in the main cube will have at least one black side exposed.

In puzzles made up of larger numbers of elements it might be desirable to colour each exposed side of the assembled cube differently (as in a"Rubik's Cube" (TM) ). Alternatively, it might be decided to make such puzzles slightly easier by colouring all initially exposed sides the same.

If the additional element (for example element 20d) is detached from the main cube 30, it should be ensured that the orientation of that element is the same when it is re- attached to the puzzle as it was when it is removed, i. e. its first, second etc. sides are aligned with the corresponding sides of the other elements.

In this respect, in the embodiments shown all of the elements 20 have six equally-sized square sides, so that the elements are of basic cubic shape. In such embodiments it is possible to re-orient a removed element relative to the remaining elements before that element is reintroduced into the puzzle. Thus, it will be understood that an element can

be rotated about the diagonal line interconnecting the corner 31 (the corner where the first 11, second 12 and third 13 sides meet-see Fig. 6) and the corner 32 (the corner where the fourth 14, fifth 15 and sixth 16 sides meet - see Fig. 5), and rotation about that diagonal line will result in three different orientations of the element 20 where the arrangement of first and second interconnecting means is identical. Thus, rotation about the diagonal line 31-32 will change the positions of the first, second etc, sides in the three possible orientations, but because each of the first, second and third sides has an identical first interconnecting means 21, and the fourth, fifth and sixth sides each have an identical second interconnecting means 22, the positions of the interconnecting means 21,22 is the same in each of the three orientations.

If a removed element is re-oriented by rotating it about the diagonal line joining its corners 31 and 32, it may not be possible subsequently to rearrange the elements to solve the puzzle. Thus, whilst such reorientation would not affect the positions of the first and second interconnecting means (so that the element could be re-introduced into the puzzle), it would affect the positions of the first, second etc. sides, so that the differential colouring of those sides would no longer match the required position for that element in the solved puzzle. For example, if the exposed sides 13,15 and 16 of the element 20a are coloured white and the unexposed sides 11,12 and 14 are coloured black the element 20a can be placed in its correct orientation in the position shown in Fig. 7, with all of its white surfaces exposed (to match the white exposed surfaces of all of the other elements in the main cube 30). It will, however, be understood that the rotational symmetry of the elements 20 about the diagonal line joining their corners 31 and 32 allows the element 20a to be re-oriented in the position shown with the exposed sides being the first 11, the fourth 14 and the fifth 15, and further re-oriented so that the exposed sides are the second 12, the fourth 14 and the sixth

16. In both of these alternative orientations the positions of the first interconnecting means 21 and the second interconnecting means 22 are unchanged in position relative to the other elements in the puzzle, but some of the exposed sides are now coloured black instead of white.

It is therefore desirable to avoid the possibility of inadvertent re-orientation of a removed element, and to ensure that a removed element is reintroduced in its correct orientation, the sides of the element can be marked so as to enable the user to orient the removed element correctly as it is reintroduced. Thus, provided that at least one of the sides (e. g. the first side 11) is identifiable in some way then it will be possible to ensure that the first side 11 is aligned with all other first sides 11 when the removed element is attached to the main cube.

It would be possible to construct a puzzle from just the elements 20a-h of Fig. 7, since the respective lines of elements can all be pushed relative to their neighbours (substantially in the direction of any of the three perpendicular axes) to cause an element to project from the main cube. However, that would cause a void to remain within the"cube"of remaining elements. Whilst the projecting element could be detached from the remaining elements and re-attached to push another element into the void (and at the same time mix up the elements in the puzzle) the need to fill the void would reduce the number of choices available to the user. It would also be possible to assemble the puzzle from elements 20a-20g only, so that the position occupied by element 20h in Fig. 3 is empty. The user could then slide either element 20d, element 20e or element 20g into the void, and then slide successive elements into the succesive voids left in the puzzle. Once again, however, the number of choices available to the user are more limited and such embodiments are not preferred.

Accordingly, it is preferred that the puzzle comprise sufficient elements to provide a continuous (e. g. cubic) structure without a void, such as the main cube 30 of Fig. 7 comprising eight elements 20, or the main cube 36 of Fig. 8 comprising twenty seven elements 20, together with one additional element projecting from the continuous structure.

In the latter embodiment the puzzle would be similar to that of Fig. 9 comprising the main cube of Fig. 8 and an additional element 37). Alternatively of course the puzzle could comprise the main cube of Fig. 7 and an additional element such as 37, or could comprise sixty five elements (in which case each axis of the main cube has four elements) (and so on).

Since the elements all maintain their relative orientation within the puzzle, it is not necessary that they have a basic cubic structure. Thus, one or more of the first, second and third sides (and correspondingly the sixth, fifth and fourth sides) can be other than square. It will be necessary, however, that each element has six rectangular sides, whether those sides are square or not.

It will be understood that repeatedly pushing an element into the main cube so as to push another element out of the main cube, sliding the expelled element across (and perhaps around) the surface of the main cube and pushing it back in so as to expel another element, mixes up the elements in the puzzle. When the elements have been mixed up as desired by the user the user seeks to solve the puzzle by moving the elements back to their initial positions. Solving the puzzle does not necessarily require all of the earlier movements to be memorised and reversed.

If the user is unable to solve the puzzle it can be disassembled if desired, i. e. each element can be separated from its neighbours. The puzzle may then be reconstructed by the user with the elements in their correct initial positions.

It will be understood that when seeking to disassemble the puzzle into its separate elements it is not possible to remove an element from the main cube without first sliding the element to be removed so that it lies outside the main cube ; in this way, the puzzle can be disassembled one element at a time. Alternatively, a complete line of elements (such as the elements 20a and 20b of Fig. 7, or the elements 20a, 20b and 20c of Fig. 8) can be removed for subsequent separation into individual elements, or a complete row (such as the elements 20a-20d of Fig. 7) can be removed and subsequently separated into individual elements.

In the preferred embodiments shown the elements have mechanical interconnection means, i. e. the plates 23 and ledges 25 engage one another to retain adjacent elements together. Alternative interconnection means can be provided if desired, for example magnetic means. In such embodiments, a first magnetic material can be arranged on the first, second and third sides and a second magnetic material (or a material susceptible to magnetism) arranged on the fourth, fifth and sixth sides.

It is preferable that the sides of the element have some form of detent means to retain adjacent elements together.

Thus, the first, second and third sides can carry a small projection (perhaps located at the centre of the respective plates 23), and the fourth, fifth and sixth sides carry a corresponding depression into which the projection can locate when adjacent elements are positioned accurately. It can be arranged that the material from which the elements is made is sufficiently resilient to allow the user to force the projections out of the depressions when a line of elements is to be slid relative to its neighbours, but the detent means will limit or prevent inadvertent movement between neighbouring elements and will serve to maintain adjacent elements with their sides aligned.

The detent means can if desired additionally serve to differentiate and so identify the first, second etc. sides as shown in Fig. 10. As above indicated, it is desirable to ensure that an additional element which has been separated from the main cube is reintroduced in its correct orientation. Fig. 10 shows a plan view of the plate 23 of the first 11, second 12 and third 13 sides of a further embodiment of element used to assemble a puzzle. Each of the plates 23 of the first, second and third sides carries a number of projections 33, the number and positioning of the projections differing between each of the sides so that the respective sides can be differentiated and identified. It will be understood that the respective fourth, fifth and sixth sides have cooperating depressions so that only the first side (when correctly oriented) can cooperate with the sixth side, only the second side (when correctly oriented) can cooperate with the fifth side, and only the third side (when correctly oriented) can cooperate with the fourth side. By comparing the projections or depressions on a removed element with the depressions or projections on the side of the main cube to which the removed element is to be re-attached, it will be relatively easy to ensure that the removed element is correctly oriented.

It is of course not necessary that the detent means be upon the plate 23, and the detent means could instead be located upon the ledges 25; in such an embodiment the detent means could also identify each side, for example by comprising two projections (on opposed ledges) on the fourth side, three projections on the fifth side and four projections on the sixth side.

Also, it can be arranged that the size of the projections varies according to the number, so that the sides with fewer projections have slightly larger projections and the sides with more projections have slightly smaller projections, so as to seek to equalise the force required to move adjacent elements relative to one another, during which the

projections must be forced out of their respective depressions.

Alternatively or additionally, the detent means on the first side and the sixth side can be a first shape (e. g. circular), the detent means on the second side and the fifth side can be a second shape (e. g. square), and the detent means on the third side and the fourth side can be a third shape (e. g. shaped like a star or"+"symbol).

It is not of course necessary that the detent means also act as the identifier for the sides, and an identifier on at least one of the sides which is separate from the detent means (if provided) can be used if desired.

Another possible means of identifying the respective sides would be to provide different interconncting means on each pair of sides. Thus, in the embodiment shown the first interconnecting means on the first side is identical to the first interconnecting means on the second and third sides, and similarly for the second interconnecting means on the fourth, fifth and sixth sides. In other embodiments, however, the first interconnecting means on the first side can differ from the first interconnecting means on the second and third sides, and similarly with the second interconnecting means. One possible difference could be in the size of the neck and plate, and the corresponding sizes and/or positions of the ledges and supports, ensuring for example that the first interconnecting means of the first side could not cooperate with the second interconnecting means of the fourth or fifth sides.

The above-described embodiments describe puzzles in which every element is movable relative to its neighbours. In a puzzle having a main cube such as that of Fig. 7 and an additional element, the number of possible combinations of those nine elements is 362,880 (or 9 !, since the first element can go in nine possible positions, the second eight

possible positions and so on). In a puzzle such as that of Fig. 9 the number of possible combinations of those nine elements is over 3 x 1029 (or 28 !, since the first element can go in twenty eight possible positions, the second twenty seven possible positions and so on). If it is believed that the number of possible combinations is too high, so that the puzzle is too difficult to solve, then some of the elements in larger puzzles may be relatively fixed, so reducing the number of possible configurations.

Fig. 11 shows an exploded representation of a puzzle having twenty eight elements, of which only the twenty seven elements which form the main cube are shown. For simplicity, the elements are shown without the connecting means, though it will be understood that each element could have interconnecting means such as 21 and 22 of the embodiments of Figs. 3-9.

The twenty seven elements shown can be assembed into a main cube having a 3 x 3 x 3 structure (such as that of Figs. 8 and 9), a first row comprising the nine elements 20a-20i, a second row comprising the nine elements 120a-120i, and a third row comprising the nine elements 220a-220i. When so assembled, it will be understood that an additional element can be connected to the main cube at a chosen position and introduced into the main cube, so pushing out one of these twenty seven elements, as described above in relation to Fig. 7.

If all of the elements in the puzzle of Fig. 11 were free to move relative to its neighbours the puzzle would have over 3 x 1029 possible configurations. If it was desired to reduce the complexity of the puzzle several of the elements may be permanently secured together so as not to be relatively movable. For example, the elements 20e, 120b, 120d, 120e, 120f, 120h and 220e could be secured together (or constructed integrally with one another), so that these elements formed a rigid sub-structure in the form of a three-dimensional cross upon which the remaining elements would be movable.

Providing a rigid sub-structure in this way would reduce the number of possible configurations of the puzzle to 5 x 1019 (21!). Also, such a sub-structure would provide added rigidity to the puzzle, and allow each of the twelve elements positioned at the middle of each edge of the main cube (20b, 20f, 20h, 20d, 120a, 120c, 120i, 120g, 220b, 220f, 220h and 220d in the arrangement of Fig. 11) to move in only one direction relative to the other elements in the puzzle, and each of the eight elements positioned at the corner of the main cube (20a, 20c, 20i, 20g, 220a, 220c, 220i and 220g in the arrangement of Fig. 11) to move in three substantially perpendicular directions relative to the other elements in the puzzle.

In a less preferred puzzle design, the interconnecting means can allow adjacent elements in an assembled puzzle to move only in the X and Y directions shown in Fig. 3, so that relative movement in the Z direction is not possible. To achieve this, the ledges and supports on side 15 which are visible in Fig. 3 can be joined together, as can the ledges and supports on side 16 which are visible in Fig. 3.

Alternatively stated, as shown in Fig. 4 the upper pair of ledges and supports on each of the sides 15 and 16 are joined together and the lower pair of ledges and supports are similarly joined together so that an interconnected element can only slide sideways relative to the element shown, and cannot slide upwardly and downwardly.

Restricting the relative movement of the elements in the puzzle in this way reduces the number of movements available to the player, but does not reduce the overall number of possible configurations of the puzzle. Adjacent pairs of flanges and supports on the fourth side 14 can be similarly joined together if desired.