Dioxoid

Dioxoid is a 1982 game by Ken Totten, published at Tau-10 Games.

The game is supposed to represent an oxygen molecule (O₂) where the large circles are the nuclei of the two oxygen atoms.

The rules:

• Setup: each player places his eight pieces (called electrons) in the marked double circles.
• On his turn, the player moves a friendly electron to an empty circle.
• If an electron moves or bounces to a circle adjacent to two other electrons, those must bounce away from the first (moving to adjacent empty circles in the opposite direction).
• If an electron moves or bounces to a circle adjacent to another electron that cannot bounce (e.g., is at the edge or near a nucleus), then it is the first electron that must bounce away in the opposite direction.
• These bounces might produce a chain reaction, bouncing more and more electrons until all stabilize.
• Ko rule: a move cannot repeat the position of the moving player's previous turn.
  
• The player that first move his electrons to the adversary's double circles wins the game.
• However, if the other player can finish in the next turn, while also being the player that started second, then the game is a draw.
  

note: the rules are not specific to where the bounced electrons should go to. But considering the chemical metaphor, and the rules stating that a piece at the edge cannot be bounced, I assume the bounce must be in the opposite direction of the moving electron.