Three lanes, one doctor. W and S move between them; A and D walk you up and down the line. Hold Space to administer doses down whichever lane you are standing in.

On a phone: hold your left thumb anywhere on the left half and drag — a stick appears where you touched. Rest your right thumb on the right half to administer. Both work at once.

Everyone in the queue wants their shot. Reach them before they walk the whole length of the room. A single person takes one dose, a family several, and a whole coach party a great many — the bar above their heads shows how far along they are.

Anyone who reaches the end unserved costs you coverage. Five gaps and the clinic has lost control of the day. Nobody is ever a threat to you; the only thing you can lose is the chance to help them.

Every person you see to teaches you something. Fill the bar and you bank a talent point. The queue keeps moving — spend it when there is a lull, with E or the button at the bottom, and time stops while you pick one of three cards. Points keep, so you can hoard a few and spend them together.

Past level four the great programmes unlock. A Mass Clinic that sees the whole street at once; a Mobile Unit; a Walk-In Queue that forms around you; a Community Drive that carries a coach party's goodwill down the whole road.

Every shot breaks a chain. The one you give today stops the infections that would have followed from it, and the ones after those — so the count doubles and redoubles as the outbreak runs. By about the tenth day one clinic's work is measured in billions.

Then the variants arrive, and the number that matters becomes the whole global population still exposed to them. Get it to nothing and there is nowhere left for the thing to go.

W / S change lane A / D back and forward Space hold to administer E spend a talent point or tap a lane on touch

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