Atomix takes place on a playfield, consisting of a number of walls, with the atoms scattered throughout. The player is tasked with assembling a molecule from the atoms; more specifically, the atoms must be arranged into a specific shape, identical with the shape of the molecule displayed on the left side of the screen. The player can choose an atom and move it in any of the four cardinal directions; however, a moved atom keeps sliding in one direction until it hits a wall or another atom. Solving the puzzles requires strategic planning in moving the atoms, and on later levels with little free space, even finding room for the completed molecule can be a problem. Once the molecule is assembled, the player receives score; the faster the puzzle is completed, the more score is given.
Source: Wikipedia, "Atomix (video game)", available under the CC-BY-SA License.