Note you need to collect the little guys, not kill them. And also I think that’s what the meter is for in the bottom-right, to indicate how many people you rescued and thus your firepower level.

Also, looking at a FAQ, seems you can actually take unlimited hits if you’re saavy enough to avoid getting hit once the music changes to the “near death” music and then back, which refills your health.

Perhaps just Mike can revisit the game and show us how badass he can be at the game once he better understands the mechanics 🙂