Marko, I agree with you about the difficulty settings.
We need to first get the main game working in Tip-top shape, then we can worry about smaller details.
And Jourdy, if I remember correctly, GIMP handles animation by layers that translate into frames, right? You should use the transparency settings and make sure your sprite is oriented the same as in the previous frame, or you get a GIF that looks like that, jerky and unprofessional. The sprite itself isn't BAD, but the way its back changes color will make it unusable against an actual background.
Also, if you observe a bird, its back doesn't slope upward to meet its neck, it curves downward.
EDIT: the way I would handle difficulty levels is changing the starting level. IE; if you choose easy(cowardly), you begin at level one. Medium starts you off slightly farther in, somewhere around 5 or so, and Hard starts you off at level 8-9.
That would be the most practical way of doing a difficulty setting, but don't worry about it just yet.