Select a device to read how it works, see its truth table and, for adders, decoders, multiplexers, latches, flip-flops, counters and registers, the gates inside it.
Drag the background to pan, Ctrl/⌘ + scroll or pinch to zoom. Drag from an output pin to an input pin (or tap one, then the other) to wire.
Tutorials
1. Wire your first circuit
- Tap a switch to flip it between 0 and 1 and watch the wires turn gold when they carry a 1.
- Add a new gate from the palette. Drag it by its body to move it; it snaps to the grid.
- Wire it: press an output pin (filled dot) and drag to an input pin, or tap one pin and then the other. Tap a wire to remove it.
- Select any device to read about it and see its truth table under the canvas.
2. Remember a bit with a latch
- This loop of two NOR gates has feedback. Turn S on then off: Q stays 1.
- Turn R on then off: Q goes to 0 and stays there. That is one bit of memory.
- Turn S and R on together and release both: the result is unpredictable on real hardware, that is the forbidden state.
- Try the D latch (NAND gates) example next: it adds an enable so you can load data safely.
3. Count with flip-flops
- Press Run. The clock drives the first T flip-flop; each following stage divides by two.
- Open the Timing diagram to see CLK and every LED as waveforms.
- Pause and use Step ½ to move the clock one edge at a time and see exactly where each flip-flop changes.
- Change the speed menu to slow it down or speed it up.
4. Store data in RAM
- The first block is the address, the second is the data. Both are 4-bit switch blocks: tap a bit to flip it.
- Switch WE on and press the button: the data is written at the address on the rising edge.
- Change the address and the display shows the other words; go back to read the stored value.
- Select the RAM to see all sixteen words and edit them directly.
5. Build your own chip
- Build any circuit from switches (inputs) and LEDs (outputs). Switches and LEDs are ordered top to bottom.
- Type a name and press Save as chip. It appears under Chips in the palette and works like any other gate.
- Chips can be nested inside other chips. They cannot contain memory or feedback loops yet.
- Export the circuit as a file or copy a share link to send it to a friend.
The canvas is unbounded: pan and zoom freely. Drag from an output pin to an input pin to wire, tap a wire to remove it, and hold Shift (or turn on Box select) to drag a selection box. Shift-click adds to the selection; Ctrl/⌘ + Z, Y, C, V, D and A undo, redo, copy, paste, duplicate and select all, and the arrow keys nudge the selection. Switches toggle on tap, buttons are held, 4-bit blocks flip one bit per tap, clocks run at the chosen speed (Pause, Step ½ and Step 1 move them by hand). Feedback loops such as an S-R latch built from NOR gates are simulated and remember their state. Clocked devices need a Clock or Button on their CK pin; address pins are least significant first. ROM and RAM hold 16 words of 4 bits that you edit by selecting them. The 7-segment display reads its four pins as a binary number, top pin lowest bit. Saving makes the whole circuit a chip whose switches and LEDs, top to bottom, become its pins; chips can’t contain memory or loops. Your work is autosaved in this browser, and you can keep named circuits, export or import a file, or copy a share link.