Check out the experimental WebRTC two-player real time version of the game here
The objective of Chain Reaction is to take control of the board by eliminating your opponents' orbs.
Players take it in turns to place their orbs in a cell. Once a cell has reached critical mass the orbs explode into the surrounding cells adding an extra orb and claiming the cell for the player. A player may only place their orbs in a blank cell or a cell that contains orbs of their own colour. As soon as a player looses all their orbs they are out of the game.