I just tried running your game on my Ubuntu 18.04 machine and it failed to run. As a check, to verify that my machine could run app images, I was able to successfully run, and use, balenaEtcher-1.5.33-x64.AppImage, from the command line.
py[3.7.2] gino@gino-dell:~/Downloads
$ ls -ltr
total 11820
-rwxr-xr-x 1 gino gino 12094664 Feb 4 07:36 amber-x86_64.AppImage*
py[3.7.2] gino@gino-dell:~/Downloads
$ ./amber-x86_64.AppImage
Segmentation fault (core dumped)
Segmentation fault (core dumped)
Segmentation fault (core dumped)
Segmentation fault (core dumped)
/tmp/.mount_amber-yxXDEM/AppRun: 11: exec: : Permission denied
py[3.7.2] gino@gino-dell:~/Downloads
$ cksum amber-x86_64.AppImage
4915968 12094664 amber-x86_64.AppImage
py[3.7.2] gino@gino-dell:~/Downloads
$