Swarm-like

Swarm-like is a genre in video games.
It is most often an arcade like game in which players have to narrowly avoid enemy attacks with only a single health point — much like in a Bullet Hell.

"I just played Devil Daggers and Swarmlake and they are pretty genre defining for Swarm-like games."
"I am pretty sure Super Hot has some Swarm-like elements in their endless mode."