Players can only place a sphere in an empty block or the one filled with their assigned colored spheres.
When two or more spheres are placed together in the same block, they collates and becomes unstable.
Each block has certain capacity to contain these spheres at a time. i.e. Blocks in the corners can only handle 1 sphere. Blocks at the grid edges other than corners can hold 2 spheres and Rest of the blocks can contain upto 3 spheres.
When a player tries to insert more sphere than the block capacity:
The unstable spheres reacts & explodes.
Each adjacent blocks receives a sphere, existing sphere gets
overlapped & converted to the same color.
The explosions might result in overloading of the adjacent blocks and the chain reaction of explosion continues until every block becomes stable.
The winner is the one who eliminates other players by overlapping their existing spheres on board.