Start by dropping your first Token on any empty square.
From then on place the next Token on a position diagonally adjacent to your previous Token. (There are 20 such adjacent positions in general; if the Tokence where small cubes, then next cube would touch the previous one at an edge or a corner only).
As a help you can press function key F7 to see where you can go.

The last 30 Tokens you put down are specially colored. This makes it easier for you to see where you have gone in recent moves.
The newest Token is always coloured white, the previous light yellow and so on.

You win if you manage to cover all 125 positions.

Once you managed to win, start on a different position next time.

Variant 2: same as variant 1, but with different board graphics.
Variants 3 and 4 are much easier: here you walk through a 4x4x4 cube.
Variant 5: 2x5x5 block
Variant 6: 4x5x5 block
The solution to variants 4,5,6 are attached.

Please note there are two alternative piece sets available, especially designed for the new board graphics in variant 2 and 4 !

 
More freeware as well as real puzzles and games at my homepage http://karl.kiwi.gen.nz.