A stone blindly scatters simple bombs through memory in the hope of hitting an opponent. Modern stones are normally small, fast, score well against scanners and lose to paper. Other components are sometimes paired with stones, for example stone/imps and paper/stones. The first stone was demonstrated when A K Dewdney introduced Core War in May 1984.

Transposition Stone

One effective technique is to move instructions around in a pseudo-random pattern, incrementing one location while bombing another. After each pass through memory stone contains MOV >0,x. When executed x is incremented, shifting the next pass forward by one. Most of memory is bombed before the stone self-destructs.

        step   equ 1185           ; mod 5

inc     spl    #-step,   <step
stone   mov    >step,    1-step
        sub    inc,      stone
        djn.f  stone,    <5555

Self-Bombing Stone

Another effective technique is to bomb with a custom DAT which converts the stone into a suicidal core-clear. As the stone finishes bombing it drops the final bomb at hit. This continuously increments the b-field of stone to perform a simple clear.

        step   equ 953
        time   equ 3382

        spl    #0,       0
stone   mov    bomb,     hit+step*time
hit     add    #-step,   stone   ; bomb dropped here
        djn.f  stone,    <5555

bomb    dat    >-1,      {1

Further Reading

  1. Kline, Paul. "Silver Bullet." Core Warrior 65 (6 Feb 1998).
  2. Morrell, Steven. "Stones." My First Corewar Book. Self-published, 1994.
  3. Tomašev, Nenad. "Exploring Stones — The Basics." Core Explorer 2 (24 Nov 2005).