Click the 5x5 board.
25 square tiles with red and blue path pieces will be dropped by the system onto the board.
Each square tile is different (the full set of path tiles has 96 pieces).

Click two tiles to make them swap places.
Or click a tile, then an empty position to move a tile to an empty position.
Markers at the border will remind you which from- and to-position you have selected.
You can also click the same position twice to rotate a piece clockwise.
However, only five such rotations are allowed! A counter at the lower left border will show you how many rotations you have used up.
(In the 'easy' variants the rotations are not limited, see below).

You win when you have created a loop (or, failing that, a continuous path) using all red (or all blue) path pieces.

Beginners level: as described above
Expert level: create a continuous red path without ever placing a tile onto an empty position.
Once you solved the puzzle for the red path, solve it for the blue path.

The win-condition in this game is very forgiving:
The very first and very last last tiles of the continuous red path are allowed to join onto a blue path piece. Of course, it is preferable to find a continuous red path where this is not the case.

Variant 2: 6x6 board
Variant 3: 7x7 board
Variant 4: 8x8 board
Variant 5: 9x9 board
Variants 6,7,8,9,10: like variants 1 to 5, but with unlimited rotations of the tiles.
Variants 11 to 20: cards can occur more than once.

 
Related Zillions games: Loop, Trax.