This bizarre roguelike has a new take on the Vampire Survivors formula: letting you build your own custom weapons out of brains, eyeballs, and chimpanzee spines

A little over two years ago, I was taking my first run in Vampire Survivors, walking around a barren plain smashing skeletons with my whip. Now it's 2025, and I'm stitching together a chain of chimpanzee spines and tentacles to connect to my third brain, so I can make it through the next round of laboratory testing. I don't know if I fully understand where this genre is going, but I'm into it.

Bio Prototype's core twist on the Vampire Survivors formula is that, instead of simply choosing a weapon from a set list, you instead build your own custom weapons out of looted components. It's essentially a simple programming system—you make chains of if/then statements which output as your attacks. Weirdly it's reminiscent of a production line in something like Factorio, just producing storms of projectiles instead of refined steel ingots.

Rather weirder is what you're actually making chains out of. Rather than a gothic vampire hunter, in Bio Prototype you're… well, the clue is in the name. As a gloopy little science experiment, you bounce around sterile test chambers blasting hordes of other freaks. As such, your weapons aren't guns, but are instead disgusting webs of organs and other body parts.

Each weapon starts with a brain. A brain can connect to a spine, which is like your engine—it automatically activates whatever nodes are immediately to its right at a regular interval and level of "efficiency" (a power multiplier). We can connect that to something that generates an attack, like a tentacle (for shooting) or a limb (for melee swipes). That part will itself have specific other parts it can connect to, often nerve clusters or eyeballs—these bring in your if/then statements, like "If the node to the left performs a critical hit, the node to the right will trigger". Stick another offensive part on after that, and the layers are starting to build.

The result is brilliantly chaotic, even in the relatively simple early stages. You might have a swordfish tentacle (hmm), powered and buffed up by a chimpanzee spine, that fires a rapid stream of bullets, each of which causes an explosion if it kills an enemy because it's connected to a "germ rat" limb (which looks like a mushroom, of course). If that explosion hits any uninjured enemies, then your clown nerve (???) activates and triggers your giant bone protrusion to smash any remaining stragglers.

And that's before you even get into branching chains (rare spine and nerve drops can support multiple node paths) and, of course, multiple brains—you can buy extra grey matter over the course of a run, naturally, allowing you to build out multiple complimentary weapons.

Try to stack too many effects on the same bit of brain and the message "insufficient brain capacity" will flash up, which is sometimes how I feel playing it. Juggling all this cause-and-effect in your head and optimising your fleshy weapons can be a little disorienting, and definitely asks for a bit more thought than even other examples in the genre that focus on layered character-building, like Halls of Torment or Deep Rock Galactic: Survivor.

But it's an intriguing level of depth for a game that could have coasted just on pure gory novelty. I was probably always going to like a game where one of the key steps of progression is unlocking the ability to have a bladder—that there's a cool and complex system underneath the goopiness is a bonus.

In fact, what's frustrating about the demo is that it cuts you off just as you're starting to explore the possibilities. You can only play with one character at the lowest difficulty, and the pool of possible organs is strictly limited—and even though I've apparently unlocked more types, I'm yet to see them ever appear in a run. It's a tantalising tease, and I'd love to get a slightly better sense of how it develops from here.

But hey, better to leave us wanting more than already having had our fill (of spines and bladders), right? There's not too long to wait for the full version, at least—release is planned for January 20th. In the meantime, you can check out the demo yourself for free on Steam, and see what scientific abominations you can cook up yourself in the name of pushing your damage numbers ever higher.