The game looks very good.
It crashed when I launched it and kept crashing until I changed my regional settings to US English. Sascha, did you test the game when decimal separator is "," instead of "."? I think the problem is here.
A tutorial would be very useful for a freeware game and absolutely necessary for a shareware one. Have no idea how to play it.
GUI screens/menus are fading too slow IMHO.
Anyhow, good work!