Springline

Springline is a 1976 game by D. Thurston, published by Pentangle.

The game is played on the following board,

Each player has eight pieces that are placed on their side of the board, marked by the dots and in the three corners (the return pads):

The rules:

• A piece can move to an adjacent empty hex, or slide over a line of empty hexes
• Three friendly pieces form a springline. A player, instead of moving a piece, may release either piece on the end of a springline. A released piece also slides over a line of empty hexes, bouncing off the edges, as far as the player wants. 
• A released piece is stopped before meeting a friendly piece
• If the released piece meets an enemy piece, the enemy piece is captured by replacement, and becomes a prisoner (it is placed on the three circle reserve seen outside the board).
  
• If both players have a prisoner, they must be exchanged and placed immediately on one of the return pads. If a player has all return pads occupied (regardless of whom), it loses the game.
  
• Another winning condition occurs if a player has, at any moment, three prisoners.
  

an example of a released piece
bouncing at the edge of the board

Considering the previous diagram, I assume a frontal bounce-off at a corner might go either left or right 60º, as the player decides.

Ralf Gering, in a comment at BGG, notices the possibility of repeated positions, where a released piece stops at another friendly springline, which can send the piece to its initial position on the next turn. If that happens with both players, a Ko rule is probably needed.

Here's a review from Games & Puzzles magazine: