Available options are:

-h / --help

Print this help message and exit.

-v / --version

Print the version number and exit.

Window options (backend GTK+):

--geometry WIDTHxHEIGHT<sign>XOFF<sign>YOFF

Set initial window size and/or position.

--fullscreen

Set initial window size to cover whole screen.

--fullscreen-custom WIDTHxHEIGHT

Try to resize the screen to WIDTHxHEIGHT and then set initial window size to cover whole screen.

--display DISPLAY-NAME

Use given X display name.

--no-limit-fps

Disable FPS limit. Use this, and turn OFF vertical synchonization in your GPU settings, to get maximum FPS.

Full documentation on https://github.com/castle-engine/castle-engine/wiki/Curves-tool

castle-curves version 2.0.0. Created using Castle Game Engine ( https://castle-engine.io/ ) version 6.4. Compiled with FPC 3.2.0 (Linux / x86_64).