In the menu, you have to move on the planet you want (new game or credit) and use enter to validate.(it's write in the instruction).
It's must be add to the tutorial.
no it's really not all working on Linux not because of my connection, i can't use 1,2,3 and 4. I know I can use A,S,D and F but it's harder and I don't have a QWERTY keyboard(I'm French...)...