Atoms or Chain Reaction

Atoms is usually played on a 8×8 board, though other sizes occur as well and some implementations let you choose the size. When it's your turn, you can put a piece in any square where there are no pieces of your opponent. Each square can hold as many pieces as it has direct neighbors: a corner square two, a side square three, all the rest four. When the number is exceeded or reached (both variants exist, though the latter seems to be the original one), the square will explode, throwing the pieces on the neighboring squares. If there are any opponent pieces on these squares, they will be converted. If any of these squares already hold the maximum number of pieces, they will explode too, demonstrating the aptness of the name Chain Reaction that seems to be the most common one. Since this name is fairly popular for Columns implementations as well, I generally refer to the concept as Atoms.

The Origins

About the history of the game I mainly know what the various authors told me in emails or wrote in their documentations. One thing is clear: Atoms started out as a BASIC game for 8-bit machines.

Eirik Milch Pedersen says about the inspiration of his implementation, Atomic:

I got my idea from an old issue of Personal Computer World (1986?). At that time they used to include sourcecode in the magazine for people to type in. One of these games was Atoms, and as far as I remember it was a clone of a game made for an MSX(?) computer, written in Basic. I liked the idea of the game, and saved the description in a desk for some years. During summer 1991 I had aquired sufficient knowledge to make my own version.

Jonas Olsson says he played it first as a BASIC game with the name Meltdown on his Amstrad CPC.

Frank Van Camp credits some of the text in his documentation to BEEBUG magazine Vol. 3 No 8 Jan/Feb 1985 and refers to the game as of Scandinavian origin.

16-bit (and 32-bit) Atoms

I found three Atari ST implementations: one by B. Hewlett (Atoms, 1989), one by Stephen Taylor (Chain Reaction, 1992), and Plop by Digi Tallis (1992). I'm not sure about Amiga. There are no games named Chain Reaction on Aminet, and of those named Atoms at least some are Black Box implementations.

On the PC, it enjoyed a somewhat explosive (tee-hee) popularity in the early 90s, mainly on DOS. The oldest implementation is by one A.R. Wright, about whom I could find out nothing at all. Two are from the Czech Republic. Then things became a lot slower, but the concept never really died.

Nearly all the PC implementations are from Europe, and here mainly the northern part. The strange Yiff! is the only one definitely from the US.