Core War (KotH)
Email Redcode warriors to compete on Core War hills
KOTH.org runs hills for Core War, a classic game for programmers. You write a warrior in the Redcode assembly language. Warriors share one block of memory and try to make each other's code stop running. When you send a warrior to a hill, it fights every warrior already there, and the lowest-ranked one is pushed off.
Free · No login · Desktop · Advanced
About Core War (KotH)
The game is old and deep. A warrior that stays on a hill takes real skill, so this suits patient programmers who like low-level puzzles.
You write and test warriors on your own computer with a simulator such as pMARS. Then you email them to the server, with a ;redcode line at the top to pick the hill. There are seven hills with different rules, such as ICWS '88, '94, experimental and multi-warrior. The site also has guides and a Slack server.
On Breakpoint since 23 Oct 2026.