Enigma is a puzzle remake of Atari’s Oxyd. The goal is to roll your marble around so that it hits the special Oxyd stones (usually they are located along the level’s outer walls, like the black stones in the screenshot below), which then open to reveal a coloured tile. You can open two at a time and have to match each pair together to solve the level. That sounds easy right? The fun part is that each level has tons of traps and puzzles that make it really challenging to get to those Oxyd stones!

Believe it or not, this free game has over 1,000 levels; that should keep us all pretty busy for some time!

Download: http://www.nongnu.org/enigma/index.html . Enigma is available for Windows, Mac OS X, and Linux.