0 day Attack on Earth

The sandwich enemies are the ones that try to smash you between their upper and lower halves when you fly underneath them. They show up as yellow dots on the radar (like the mosquito and snake). To kill them fly underneath them and then flip around and shoot them when they smash together. Once you've done enough damage, one half will blow up and the other half will run away. You do NOT need to chase down the half that runs away for it to count as a kill.

The kill count is cumulative across games. Co-op games count as well.