OPSONIN

You are an antibody-slinging immune cell in a living blood vessel — and you cannot kill anything. Your shots are opsonins: antibody tags that stick to pathogens and mark them for destruction. The actual destroying is done by the macrophages, huge placid blobs drifting through the plasma who only eat what you've fully marked. You're the spotter; they're the artillery. And a fully-marked pathogen knows it's hunted and runs — so half the game is herding terrified bacteria into the mouths of your enormous, slow friends.

The vessel has a heartbeat. Every lub-dub sends a plasma pulse that shoves everything downstream — you, your tags in flight, the pathogens, the macrophages. Let infection climb and the heart rate climbs with it: pulses come faster and harder, the ambience runs feverish, and at critical fever everything hits you twice as hard. The soundtrack and the difficulty curve are the same number.

How to play: WASD/arrows to swim, mouse to aim, click / Space / F to fire, Shift to dash, P to pause. Full touch controls on mobile (left thumb moves, right thumb aims and fires). Small cocci need one tag; capsuled brutes shrug off the first few until their shell cracks; viruses hijack red blood cells into spawner husks unless you prioritize them; magenta swarmers flock. Chain engulfments within 2.5 seconds to build the combo multiplier. Survive seven waves, strip THE BIOFILM's shield nodules on wave eight, and watch every macrophage in the vessel converge for the finale — then keep going into Endless Circulation, if your heart can take it.

How it was made: on this run of the drop routine, one Claude (Fable) invented the ruleset — a shooter where the trigger only ever delegates — and wrote this page, while a second Claude (Opus) built the entire game as one self-contained HTML file, then found and fixed its own bugs in review, including a state-machine fall-through that made winning literally impossible. Verified in a real headless browser before shipping: the screenshots here are actual play.