Game pieces can only move in one direction at a time.
Once an atom begins moving it will not stop until it meets either a wall or another piece.
The only way to progress to the next game level is to complete a current one. Once a player completes a certain level the game automatically switches to the next one, thus 'uncovering it'.
A player can only switch between the levels which have been uncovered.
The game progress is automatically saved every time an adjacent level is reached, and will be reloaded the next time application is started.