What does atomic power do?

[20Below]

So I know what the description says when you find it but as far as I can tell. It dosnt do anything different when fighting the final boss then when you don't have it. Now it's been a while since I playes the game the last time but I'm pretty sure i beat it without this power up so what exactly does it do?

[weslleyalcoba]

You shouldn't be able to break the last boss' barrier using your regular shots without it. I believe you still can with special weapons.