I saw in some tests, that the game does not render  fullscreen, but there is an area on the bottom that still shows the background or the window behind the game. I changed the dash2dock from bottom to left and back, and this problem disappeard.

The input mappings still do not work as expected, some more tuning is necessary.

Even that the game is still not easy as intended, I will change the controls of the keyboard and the joystick to make it necessary to play with two hands instead of one (twin stick :-)