Indie developer Dapper Dog Digital released their “love letter to the Metroidvania genre” this week with BioGun, a platforming action-adventure that takes place entirely inside a whimsically microscopic world of viruses and vaccines. And whimsically enjoyable it is, with a hand-drawn world and characters that have a wide, delightful, and cartoonish variety in their design.

As you explore the chambers and environment of the cell-eat-cell world you find yourself in, your little vaccine upgrades their DNA and modifies their playstyle using nanotech to get new powers, tweaking how they move and shoot, and earning all kinds of new guns for the side-scrolling 360-degree shooting—which I’ve gotta say feels pretty tight and controls well as of launch.

Also, the soundtrack is really, really good. It’s made by Juhani Junkala, aka Subspace Audio, and should really be on sale separately.

The plot’s pretty goofy, but fits the animation and genre well: You’re a “smart vaccine” tasked with saving the world from a “pet-demic” that threatens all good dogs everywhere, which I think we can all agree is very important work.

BioGun launched into early access this week, on April 16, and plans to be there for around three months. Developers Dapper Dog Digital have laid out a plan of adding new side missions and activities around the world, as well as at least one new character to interact with and some community events to take part in.

You can find BioGun on Steam.