Greg Harman

Open World Hack

Project Active since

NetHack 5.0 with the dungeon replaced by one huge outdoor world. The further you walk from the center, the deeper you are, and you win by carrying the Amulet back to the high altar you started on. It also adds a new role and race, plus my favorite bits from many NetHack variants.

What it is

Open World Hack is NetHack 5.0 with the Dungeons of Doom and Gehennom replaced by one huge outdoor world. The further you walk from the center, the deeper you are.

The open world is the main shtick. You start on your god's high altar in a plaza at the center of the world. Around it the land is concentric rings 16 squares wide, and your ring is your depth (Dlvl), which drives difficulty the way dungeon depth does. The status line (Home:NW 187) and a compass rose on the map point home. There are no stairs, rooms, or corridors. The land is meadows, forests, hills, mountains, lakes, swamps, tundra, deserts and ruins, with roads, towns (shops, a temple, a watch), walled compounds for NetHack's special rooms, and vaults sealed in the mountains.

Each special level is a branch behind magic portals spaced evenly around the ring at its usual depth. Gehennom is the outermost rings, walled off by the Barrier, and you still get in through the Castle and the Valley. There are no Elemental or Astral Planes. You win by carrying the Amulet of Yendor back to your god's high altar at the center.

It also adds a new role and a new race, plus my favorite bits from many NetHack variants. The new role is the Cartographer, a mapmaker and explorer made for a world of compass, rings and portals. The new race is the ghost, which drifts through walls. The rest comes from Slash'EM, SlashTHEM, SpliceHack, Hack'EM, EvilHack and xNetHack: their roles and races, techniques, object materials, and extra special levels, ported from their source and rewritten for 5.0.

Why I built it

An open-world NetHack has been my "pelican on a bicycle" test for coding models. This one, built with Opus 5.5, is the first I've been happy with.

Current state

It's public. It's a fork of the DevTeam's NetHack 5.0 branch (commit c1b1b08, 2026-09-26), and about 150 of NetHack's files are changed. The rest of NetHack still plays as usual, from character creation through the Mines, Sokoban, the Quest, Medusa, the Castle, Gehennom and the invocation.

The repository holds the source. build.sh builds it with a C compiler, make and curses, and the first build downloads Lua 5.4.8. The build has been used on macOS. On Linux it uses NetHack's Linux build settings, which haven't been tried with this variant yet. It runs in a terminal (tty only), in color, and the map fills the window, so a bigger terminal shows more of the world. Bugs go to the GitHub issues, not to the DevTeam.

What it looks like

The starting plaza at the center of the world, with the hero and a pet dog among three high altars on Dlvl 1 and the status line reading Home:here.
Starting out: three high altars. Instead of going on to the Elemental Planes, you bring the Amulet back here.
The hero on Dlvl 5 next to a magic portal inside a ring of rocks, with the status line reading Home:W 72 and the message line reading an engraving that says Mall.
Branches are reached through magic portals.
A hero on Dlvl 5, 64 squares west of home among ruined walls, with the message line reading You feel that the land grows more dangerous.
Moving outward from the origin increases difficulty.

Changelog

Code: https://github.com/gharman/owhack

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