Hello!
Great idea with the collective health thing, especially for a swarm. It had a good design and a nice difficulty curve. The art was also nice, reminiscent of the Binding of Isaac.
The audio had some issues - I think the music loop can get a bit repetitive, and in there menu music and on certain attacks that is a "click" - this is when a sound file either loops wrong or when the audio tail has been cut off not at 0 db- it's super easy to fix but is noticable.
Overall good use of theme, and clear UI!