Jump'n'Bump

Cute fluffy bunnies hop on each other's heads. Whoever bumps the most heads wins. Local multiplayer (up to 4 players, human or AI, any mix), custom levels, and UDP netplay (legacy build only, see below). Originally released by Brainchild Design in 1998; this fork is a Linux/SDL port from 2004 that's been re-platformed onto a Zig simulation core rendered by Godot.

Status

The Godot build is now the primary, fully playable way to run Jump'n'Bump: a Zig simulation core (core/) is exposed to Godot through a frozen C ABI (include/jumpnbump.h) and a GDExtension shim (extension/), and game/ wires that up into a full title -> menu -> gameplay -> scores -> menu flow with 4-local-player input (keyboard + gamepad, remappable), persisted settings, and pause/clean-quit handling.

The legacy SDL 1.2 C build (main.c, sdl/, modify/, data/) is kept in the repo forever, not as a second way to play, but as the differential-test oracle the Zig core is checked against frame-by-frame (see docs/porting-playbook.md) -- see "The legacy SDL build (oracle)" below if you need to build or run it.

See backlog/tasks/ for per-task status and docs/porting-playbook.md / docs/build-layout.md for the full architecture.

Playing it (Godot build)

Requires the pinned Godot version (see .tool-versions, installed via mise) available on PATH as godot.

task run    # fetch git submodules, build the core ABI + GDExtension shim, launch the game

task check runs the boundary + test gates for the Godot build and the asset pipeline. task deps/task submodules fetches just the git submodules (third_party/godot-cpp) on their own; task game:run launches the game without rebuilding anything.

Controls

Local multiplayer defaults (remappable in-game from the player-select menu):

Player	Keys
Dott	arrow keys (left/right/up)
Jiffy	a, d, w
Fizz	j, l, i
Mijji	numpad 4, 6, 8

A gamepad can also control a player (left stick or d-pad to move, face button to jump). Window size/fullscreen and mouse input are handled by Godot itself, not a custom flag.

Custom levels, screensaver, and netplay

These are legacy-build-only for now (TASK-016/017 track porting them to the Godot build):

jumpnbump -dat levelname.dat            # load a custom level (see levelmaking/)
jumpnbump -fireworks -fullscreen        # fireworks screensaver mode

# netplay (UDP), same -dat level on every peer:
jumpnbump -port 7777 -net 0 <host_of_player2> <port_of_player2>   # player 1
jumpnbump -port 7777 -net 1 <host_of_player1> <port_of_player1>   # player 2
# -net 2/-net 3 add a 3rd/4th player the same way

The legacy SDL build (oracle)

Not part of the default task check gate (TASK-015.05) -- build it on demand with task legacy:build (taskfiles/legacy.yml, TASK-019 -- no make toolchain required). Requires SDL 1.2, SDL_mixer, SDL_net, zlib, and bzip2 dev packages. Debian/Ubuntu:

apt-get install libsdl1.2-dev libsdl-mixer1.2-dev libsdl-net1.2-dev zlib1g-dev libbz2-dev

(macOS: see taskfiles/ci.yml's ci:_install-macos-deps for the Homebrew + from-source SDL_mixer/SDL_net setup used in CI.)

task legacy:build
./jumpnbump

task legacy:clean cleans sdl/, modify/, data/, and the top-level objects/binaries. Its controls, custom-level, screensaver, and netplay flags/instructions are in the section above; f10 toggles windowed/fullscreen, esc/f12 quits.

Building and testing

task check is the single documented gate: it runs the Godot build's boundary check (task game:boundary-check) and test suite (task game:test), plus the asset pipeline's reproducibility gates (task assets:check). taskfiles/ci.yml wires task ci:linux-check/task ci:macos-check into GitHub Actions for both platforms; both also verify the legacy oracle still builds (task legacy:build) before running task check.

core/build.zig defines the Zig side, run from core/ (zig build <step>):

• test — Tier-A unit tests for ported modules
• difftest — Tier-B differential tests against the legacy C oracle
• abi — builds core/abi.zig as a static library
• abitest — Tier-C ABI conformance tests

task game:test runs game/tests/ headlessly through gdUnit4 (Tier-D, TASK-014.07).

Architecture

Path	Purpose
core/	Zig simulation core: physics, collision, AI, particles, game loop
include/	jumpnbump.h, the frozen C ABI between core/ and extension/
extension/	godot-cpp GDExtension shim, forwarding 1:1 to the C ABI
game/	Godot 4.7.1 project -- the primary way to play
tools/	Asset pipeline + boundary/purity validator scripts
main.c, sdl/, modify/, data/	Legacy SDL/C game — retained forever as the differential-test oracle

The legacy C tree isn't dead code to delete once the port lands: it's what the new Zig simulation core is checked against frame-by-frame, so behavioral drift in the port shows up as a failing diff rather than a silent regression. See docs/build-layout.md for the full layout and docs/porting-playbook.md for the porting procedure and verification tiers.

Credits

Original DOS game by Brainchild Design — see readme.txt. Linux/SDL port credits and the upstream 2004 README are preserved in docs/legacy-readme.md.