Authors of some data assets (graphics, sound):

- crash.wav

  from https://opengameart.org/content/crash-collision
  Author:
    qubodup https://opengameart.org/users/qubodup , https://qubodup.github.io/
  License(s):
    CC0

- arrow-*.png

  based on https://opengameart.org/content/glow-arrow
  Author:
    oglsdl https://opengameart.org/users/oglsdl
  License(s):
    CC0

- speed.png

  based on https://opengameart.org/content/bolt-animation
  Author:
    IMadeIt https://opengameart.org/users/imadeit
  License(s):
    CC-BY 3.0

The rest: copyright by Michalis Kamburelis,
license "modified BSD (3-clause)",
see https://castle-engine.io/license .