Everything here is digital: a wire, gate, or output is simply on or off. Signals settle instantly, so a change at a switch reaches the far end of a circuit in the same frame. There is no delay to wait through.

Sources (Power, Switch, Button, Clock) push a signal out on all four sides. A Wire conducts from any side and passes the signal on. The directional blocks (Inverter, Buffer, AND, OR, XOR) read their input side (marked with a small notch) and emit only toward the arrow. Two-input gates also read the face to the left of the arrow.

An Inverter outputs the opposite of its input, a Buffer repeats it one-way, and the gates combine their two inputs. LEDs and Buzzers are the outputs; a buzzer beeps when it first turns on. Rotate a block with the Orientation buttons or by pressing R with the pointer over it, and erase with the Eraser or a right-click.

The idea of a signal carrying information is covered under signal.