I am also unsure about the white outline, which I think makes it harder to read at 1x. That said, it's a really cute bat and the flapping looks great with just two frames.
Wow, this is really good! Idk how I feel about white outlines in general, and my eyes are so bad that I can't tell how readable it is at 1x but I think it is a great 2 frame animation.
Fun and efficient. Not the biggest fan of white outlines either but can really see it working on those nitrome like games.