Truthgate

Each level hands you a set of inputs and a target Boolean specification. Your job is to assemble a circuit that produces the correct output for every possible combination of inputs, using only NAND gates.

• Press Add NAND, then click two source nodes (an input or an existing gate) to wire its two inputs.
• Choose which node is the circuit's output with Set as Output.
• A live truth-table harness checks your circuit against the target, row by row, match every row to win.
• You're scored on gate count against the level's par, so the tighter your build, the better.

• Desktop: click Add NAND, then click nodes to wire them; click a node and Set as Output; Hint auto-builds a step.
• Phone & tablet: tap the same buttons and tap nodes to wire, fully touch-friendly.

• Remember a NAND is just an inverted AND, feeding the same node into both inputs gives you a NOT.
• Reuse existing gates as shared inputs to stay under par instead of rebuilding sub-expressions.
• Watch the truth table as you wire; chase the rows that are still mismatched.

Truthgate turns digital logic design into a build-and-verify puzzle, showing how every gate can be built from NAND.

• Skills: digital logic, logic gates, functional completeness, circuit design
• Best for: roughly grades 9–12 (ages 14+)
• For parents & teachers: digital logic from NAND alone.

A target Boolean specification and a set of inputs is the standard form of a circuit-design problem, stated in Boolean algebra and checked against a truth table.

Requiring the correct output for every input combination, not just the ones you thought of, is the original discipline here.

That exhaustiveness is what separates logic from intuition. A circuit that works on the cases you tried is the commonest bug in hardware and software alike, and the only cure is a specification that enumerates everything — which for n inputs means 2ⁿ rows, and is why the tables grow so fast.

Truthgate turns digital logic design into a build-and-verify puzzle: NAND is functionally complete, so every Boolean function can be made from it alone. It's an original, free browser game with a date-seeded daily level and an endless practice campaign.

A free, original browser game on PlayPendium. No download, no install.