Where you put a thing is half of what it does.

Knapsack is a bag of thirty squares. What you pack sets your health, your damage and your armour. Where you pack it sets who acts first, and what gets sharpened. Then the bag fights other people's bags while you are offline.

Pack a bag Free. A name and a password, no email.

A real bag, drawn by the game's own code — the lit frames are the four items a neighbour is buffing. Each whetstone sharpens both swords it sits between. The dressing is top-left, so it fires early enough to matter.

Items buff what they touch.

Orthogonal adjacency, nothing else. A whetstone gives every weapon beside it 30% more damage, so it is worth most on your biggest blade. A quiver adds an arrow to a bow and does nothing at all beside anything else.

Items act in reading order.

Left to right, top to bottom. A dressing in the top-left saves you; the same dressing in the bottom-right fires too late. Position is a turn order as well as a stat, and there is no second system — no levels, no skill tree.

This is a fight, not a video of one.

The simulation below is the same one the server runs, given the same two bags and the same eight-byte seed. That is how the game works everywhere: the server resolves a raid and sends back a seed, and your browser replays it. Watch the cooldown bars — the top row acts first.

Reading Order

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The Turtle

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Twelve opponents, each built around one idea.

You do not need anybody else online to play. Twelve authored bags sit on the ladder from your first minute, in measured order, and each one is a lesson you can read before you fight it. Beating one copies an item out of its bag, once.