NAND²

Build a computer from a single NAND gate: from clicking relays to a 16-bit CPU with a pipeline, branch prediction and a cache. Then write the programs it runs.

You start with one NAND gate. Wire it into NOT, AND and OR, then adders, latches, registers and memory.

Every part you finish goes into your palette and becomes a building block for the next level.

• Relays · 26 levels: logic, selection, binary numbers

• Transistors · 33 levels: memory, clocks, the ALU, RAM, a Turing machine

• Integrated circuits · 21 levels: your first processor, programs, I/O ports

• Microprocessors · 85 levels: your own instructions, a stack, algorithms, robots, a RISC-V-style core

• Speed · 31 levels: pipeline, branch prediction, cache and your own game

• System · 5 levels: booting and multitasking

• Built-in code editor: assembler, HEX view, clear error messages

• Games on I/O ports: a robot in a maze, Guess the Number, Nim

• Tests that explain: truth tables and cycle-by-cycle checks show exactly where your circuit goes wrong

Circuits are simulated gate by gate, fast enough to run a whole processor live.

In era V you add a keyboard and a pixel screen, then run a first-person shooter on the CPU you wired yourself.

The section editor builds your own level chains with reference solutions, tests, briefs and hints. Share them on the Steam Workshop.

• 201 levels across 6 eras

• No black boxes: every complex part is built from parts you made earlier

• A reference card for every part

• Sandbox, Steam Workshop, achievements and Steam Cloud saves

• 13 languages