Enigma is a transport puzzle computer game based on Oxyd, and is released under the GPL. Enigma continues to be very popular as an open source multi-platform derivative of Oxyd now that Oxyd is no longer maintained. The open source Enigma has been praised in reviews

Gameplay

Enigma consists of approximately 1000 levels, known as ‘landscapes’ which may be played in any order. The player controls one or more marbles using the mouse, and interacts with the landscape purely through the marble. Levels fall into two broad categories: Oxyd landscapes and meditation landscapes. Some levels may appear to fall into one category while actually being in the other.
Often in each level, apart from the introductory ones that introduce the game gradually to the player, each level either contains a puzzle, race or many hazards (which tax the player's problem solving/logical skills, dexterity, patience and speed; these factors determine the overall difficulty of the level) which the player must solve, win or avoid or risk making the level impossible to solve (in which the player must restart it) or risk having the marble sink, fall down an abyss, destroyed or crushed. This takes away one of the players lives shown in the form of spare marbles in the inventory. The level automatically restarts from the beginning when all lives are lost, with the Oxyd colours randomly shuffled again. Some levels even are/have mazes which the player must find his/her way through.

• Scoring system

Enigma also contains a score system which tracks how fast the player finishes the level. When a level is completed, a "personal record" for the level is made. All levels have two records which the player can try to beat: PAR (Derived from the golf scoring format) and World Record. PAR usually takes some quick doing to achieve and even changes with time in the newer versions and setting a new World Record is near impossible even for the dedicated player except through sheer luck. World Records are usually formed by groups of very dedicated players who have mastered moving the marble quickly but precisely and have known the inside outs of each level.

• Oxyd landscapes

In Oxyd landscapes, being the most common level types in Enigma, players must activate matching Oxyd stones. When Oxyd stones are hit by a marble, laser beam, or certain types of moving brick, they open to reveal a coloured circle. If two matching Oxyd stones are activated they remain open, while if non-matching Oxyd stones are activated the first one closes. There are a maximum total of twelve different colours in Oxyd stones. When all Oxyd stones are open the level is complete.

• Meditation landscapes

In meditation landscapes the player must place small white marbles into hollows in the landscape, with one marble in each hollow. Meditation landscapes may feature large marbles and Oxyd stones as a distraction. Some meditation levels have too few or too many hollows, in which case the player must produce extra hollows or remove existing hollows in order to complete the level. This level type has all marbles moving together so the player has to be careful when positioning other marbles into the other holes or navigating a hazard. Otherwise, a single jolt that's too strong may send marbles that are already in the hole out, requiring the player to reposition them.

• Two player landscapes

In this landscape, the game adds an additional marble for the player to control. However, Enigma is a single-player game so the game includes a Yin-Yang item that is automatically added to the players inventory when the level is started or located somewhere around the level which the player has to find. This item, when activated, switches control between the black and white marbles respectively. Normally, this level includes special bricks which change colour to the opposite colour of the marble or only let a marble of the specific colour pass through.