The formula works, it's great, it's got a bunch of cool idea, the aesthetics of the game blend perfectly with what it's aiming to do (the way infravision works in this game is honestly perfect)
It's sadly lacking a bit on content which would make it a bit less repetitive, though I wouldn't be able to tell you what exactly would have to be added here to achieve that, I think a few more enemy types or overall threats (doesn't have to be enemies) to spice things up that isn't just 'enemy spawns and rush you and kill you', maybe tied to the infectation that you'd have to stop or slow down else it might make your life hell, also a few more environments and objective types, the upgrade system is also very obscure (and I'm expecting most people to not even know it exists or to what extent it exists)

But it's very unique and very refreshing, it feels great to play it, huge thumbs up especially for a game made by two people