Logic Gates Lab: Circuits — Wire real logic gates and prove them with truth tables

The useful test is whether you have to actually wire a circuit, not just read about one. Logic Gates Lab puts every lesson on a 3D breadboard: drag a gate, wire its inputs, press Run, and a truth table proves row by row whether it works. The course runs 34 lessons across four worlds, from the seven basic gates through adders, multiplexers and sequential logic, free on Android with iOS coming.

A truth table lists every possible combination of a gate or circuit's inputs in one row each, with the output it produces for that combination in the final column. Because inputs are finite — two inputs give four rows, three inputs give eight — a truth table is a complete description of a circuit's behaviour with nothing left to interpretation. Logic Gates Lab shows the expected truth table beside your wired circuit's actual output, with a mismatched row glowing red.

NAND is an AND gate followed by a NOT, and it's called universal because every other logic gate — AND, OR, NOT, XOR included — can be built using only NAND gates wired together in the right pattern. That matters in real chip design because manufacturing a single gate type repeatedly is simpler than manufacturing several different ones. Logic Gates Lab's Gate Fundamentals world covers NAND specifically as this universal building block.

A half adder adds exactly two bits and outputs a Sum (via XOR) and a Carry (via AND), but it has no way to accept a carry coming in from a previous addition. A full adder takes three inputs — the two bits plus that carry-in — which is what lets full adders be chained together to add numbers wider than a single bit, such as the 2-bit adder Logic Gates Lab's projects build up to.

A Karnaugh map is a grid arrangement of a truth table's outputs, laid out so that any two adjacent cells differ by exactly one input bit. That layout makes groups of matching outputs visually obvious, letting you simplify a Boolean expression by inspection rather than by applying Boolean algebra identities and De Morgan's Laws step by step. Logic Gates Lab introduces Karnaugh maps in World 2 alongside the rest of Boolean algebra.

A combinational circuit's output depends only on its current inputs — an adder or a multiplexer behaves this way. A sequential circuit has memory: an SR latch or a D flip-flop holds a value across a clock cycle, so its output depends on past inputs as well as present ones. Registers and ripple counters, built from chained flip-flops, are what let a circuit remember state rather than just react instantly. Logic Gates Lab's World 4 covers this sequential-logic layer.

Yes. All nine lessons of World 1 — every basic gate plus De Morgan's Laws, with all six of that world's hands-on labs — are free, along with an unlimited sandbox that saves 3 circuits, the Half Adder project, and the Daily Circuit puzzle every single day. Pro unlocks Worlds 2 through 4, the remaining 7 build projects up to the 1-bit ALU, unlimited Exam Mode runs, the AI circuit tutor and unlimited saved sandbox circuits.

Not yet. The app is live on Google Play now; the App Store listing exists and will show Coming soon until the iOS version ships.

It's a fresh, date-seeded wiring puzzle every day: wire a circuit that matches a target truth table within a limited gate budget. It's free forever, works fully offline, tracks a streak of your best run, and offers an optional local reminder you can turn on in Settings.

Every goal table — in every lesson, project and exam question — is computed from the same small set of Boolean functions the simulator uses to check your wiring, run entirely on your device with no server round-trip. That means a stated answer can never drift out of sync with what the engine actually checks, and grading works even with no connection at all.