README.md

DumbCycle

A simple Snake/LightCycle game for x86_64 Linux implemented in assembly and C99 with no linked libraries (no libc) and no preprocessor directives (no #ifdef, #define, #include, etc).

Images are drawn to the screen using the "dumb buffer" API provided by the Direct Rendering Manager (DRM) subsystem of Linux. Keyboard input is read directly from a keyboard device file. DumbCycle should run on any x86_64 Linux system with DRM support, a video card, and a keyboard¹.

DumbCycle can be compiled with any C compiler that supports C99 and ATT syntax x86_64 assembly. The primary motivation for eschewing the C preprocessor is to allow the project to compile using only cproc-qbe, QBE, and GNU binutils (for as and ld). Passing the game code through cproc and QBE results just over 2000 lines of simple and readable x86_64 assembly.

Building and running

Run the game by executing make run (or make run_cproc) with the required permissions¹. You can also run make and ./dumb_cycle, but make run also executes clear to automatically restore terminal when the game exits.

Playing

Steer with WASD and avoid the walls. Press ESC to exit.

References

• musl libc
• libdrm
• linux kernel
• drm_howto

Footnotes

1. The executable must have permissions to open the video device /dev/dri/card0 and the input devices in /dev/input/. No other programs should be drawing to /dev/dri/card0, i.e. you need to close your X11 and/or Wayland server. ↩ ↩²