Oxyd

Oxyd is one of the most distinctive puzzle games ever released on DOS, and one that raised its players to be patient. You control a ball, rolling it across an intricate board full of traps, and your task is to uncover pairs of colored stones. Open one, and you then have to find and open its matching pair of the same color, or both close back up again. But the path between them runs across breakable floors, one-way belts, magnets, teleporters, water, and pits, where a single clumsy flick of the mouse means losing the ball. Many levels feature two balls at once, moving as mirror images of each other, so the player has to solve two spatial puzzles simultaneously while keeping track of both bodies at the same time.

Technically, the game runs on smooth inertial physics, which sounds like a minor detail at first but is actually what makes the whole experience work. The ball doesn't stop instantly — it slides, bounces off walls, and picks up speed on inclined surfaces, so mouse control feels more like balancing than precise clicking. The graphics rely on legible tiled surfaces and clear colors, since the player needs to instantly recognize what kind of surface they're rolling onto. The sound is restrained, made mostly of clicking stones and bumps against walls, giving the game a focused, quiet feel, as if it were taking place in a laboratory.

It also became famous for its copy protection: progressing to the higher levels required codes from a printed book that had to be purchased, letting the game spread freely while still turning a profit. Because of this, many players know the first ten levels by heart and never saw the rest. The series continued with further installments, and its idea lives on in an open-source successor born out of community enthusiasm. Today, Oxyd delights anyone who enjoys games that demand fine motor skills as well as careful thought, while also serving as a reminder of a time when puzzle games weren't afraid to be genuinely hard and didn't spoon-feed the solution to the player. Anyone can clear the first few levels, but going deeper means learning to truly live with the ball.