Two programs.
One memory.
The last one running wins.

Core War is a programming game from 1984. You write a tiny program, called a warrior, in an assembly language called Redcode. It shares memory with an enemy program, and each one tries to make the other crash. Your code is the only thing that decides who wins.

⚔️ Enter the arena Learn it in 10 minutes 🏆 Take a challenge

The arena

Pick two warriors or write your own, then press Fight. Each square is one memory cell. A pale square means a warrior wrote to that cell, a bright square means it ran code there. Hover over the board to read any cell.

Choose your fighters

Warrior 1
ready
—VS—
W1 ran code W1 wrote W2 ran code W2 wrote running processes
cycle 0hover over a cell
Keys: Space fight / pause · S step · N new battle · R random matchup
Warrior 2
ready

Challenges

Nine goals, from "don't lose" to "beat everything". Accept one, write Warrior 1, press Check. Built-in warriors don't count. Bring your own code.