Skeletal animation editor - ghosting

I added ghosting to my animation editor, so it is much easier to make animations and adjust individual frames, since I can see previous(red) or next(blue) frame of animation too:

I can also render and preview all frames at once:

Simple animation interpolation

I added simple animation frame interpolation, with basically single line of code, to make the animations smoother:

current_angle = last_frame_angle + (time_elapsed_since_last_frame/frame_time)*(next_frame_angle-last_frame_angle)

Left is the original animation, right is with interpolation between frames, both slowed down: