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LOGIC GATES

AND both must be ON OR either one will do XOR they must be different NAND an AND, then flipped NOR an OR, then flipped NOT flips it: ON ↔ OFF → straight through, unchanged

Drop gates into the boxes until the light does the job — and does it in every combination of the switches, not just the one you are looking at.

How to play ▾

A box with a dashed edge is an empty slot. Tap it to swap the gate inside; the dots along the bottom show how many gates fit in there and which one you are on.

Under the light it says what it must be doing right now, with a ✓ or a ✗. Flip a switch, or tap a row of the table, and watch it change — that is how you work out what a gate does.

The gates are the puzzle. The switches are not — they are just how you test it, one combination at a time. The table has a row for each of them, and LIGHT IS NOW has to match LIGHT MUST BE on every single one, so TRY ALL COMBINATIONS runs through the whole lot in one go.

Computer: SPACE tries them all, R restarts the puzzle, ESC goes back to the packs.