Interesting mechanic! At first, I didn't realize the shadows were previous versions of ourselves. Since I was shooting all over the place, I thought, "Wow, the game gets tough right from the second level." Once I figured that out, the game got much easier—a single well-placed bullet kills the target, so it's easier to dodge. Maybe adding more enemies or moving ones would add a bit more challenge.
Also, on my end, I'm not sure if it's a bug, but there's no sound at all.
Good job !