Build a Circuit — The Foundry

One light. One rule. You choose the gate.

Two switches go in, A and B. One light comes out. Each puzzle gives you a goal, like "light only when exactly one switch is on." Your job is to pick the gate that obeys it.

Every rule, from a few gates. A handful of is enough to build every rule a computer follows. Pick the right one and the light does exactly what you want. Pick the wrong one and you can see it miss, then try again.

🔭 Why so few gates are enough

Two switches have only four settings: off-off, off-on, on-off, on-on. Any rule is just a choice of which of those four light the lamp. Because the gates cover those choices, you can build any rule by picking and combining them. That is the whole secret behind a computer.

Puzzle 1

Goal

Pick a gate, then flip A and B to test it. The table shows the goal next to your gate for every pair of switches.

A B

Light

off · 0

Pick a gate above to begin.

You wired all three.

Three goals, three gates, three lights doing exactly what you asked. That is what an engineer does, just with a lot more gates.

This is how big things get built. A whole computer is millions, even billions of these , each one a tiny rule like the ones you just picked. Stack enough simple rules and you get every game, every app, every answer.

One true fact to keep: every logic rule can be built from a few gate types. You did not need a new kind of part for each puzzle. The same small set of gates was enough every time.