The workspace and controls

This page is a tour of CRUMB: where things are, how to get around the bench, and the controls you’ll use in every circuit.

The Home screen

CRUMB opens on Home, a tab that’s always there on the left.

New Circuit Design opens a new, empty circuit in its own tab. Open Design opens a saved one.
Component Editor opens the editor for making your own parts. See Building components.
Challenges opens the learning campaign, and the big button in the middle opens it on your next challenge.
Recent work lists the circuits and parts you’ve opened or saved, newest first. Click one to open it. If a file has moved, it shows (not found) and a Forget button.
What’s new shows the latest changes to CRUMB.
Settings… opens the display settings, and Workshop opens CRUMB’s Workshop page in Steam.

Tabs, the ribbon and panels

Each circuit opens in its own tab along the top, so you can work on several at once. A tab whose circuit has unsaved changes shows (*) after its name, and CRUMB asks before closing it. The + at the end of the tabs opens a new circuit or a new component editor.

The ribbon under the tabs holds the controls:

FILE OPERATIONS: New Circuit Design, Save, Save As… and Open….
The SIMULATION tab: running the simulation, its speed, failures, and the views that colour the circuit.
The BUILD tab: wiring, bodies and joints, props, environment zones and labels.
DESIGNER LAYOUT: adding panels, and saving and loading your layout.

The rest of the window is made of panels: the 3D Viewport, the Component Toolbox (the part library), the Circuit Hierarchy (everything in the circuit, as a list), the Inspector (the settings of whatever is selected), and the Output Log. Add Tool Panel ▼ adds more, including the instruments and the serial monitor. A new panel opens as a floating window; use its menu to Dock it into the layout. Save… and Load… keep a layout you like, and Default goes back to the standard one.

The cog at the top right opens the display settings: Dark Mode, and Display Scale to make everything bigger or smaller (it takes effect when you restart CRUMB).

Moving around the bench

To	Do this
Orbit	Drag with the right mouse button.
Pan	Drag with the middle mouse button.
Zoom	Scroll the wheel.
Fly	W A S D to move, E to go up and Q to go down.
Frame the selection	F. Press it twice to follow the selection as it moves; Escape stops following.
Go back to the start view	H.
Look from the front, top, side…	Click a label on the axis widget in the corner of the 3D view.

A right-click without moving the mouse opens the context menu instead of orbiting.

The 3D view’s Settings button sets how it looks: perspective or orthographic, shadow and texture quality, render scale, the size of connection markers, and effects such as anti-aliasing, glow and Depth of Field, which blurs what’s nearer or further than the point the view orbits around. Turn effects down if the view is slow on your computer. Scene → Ground Plane is also the floor that things land on, so leave it on when you use physics.

Selecting, placing and moving parts

Select a part by clicking it. Drag across empty space to select everything in a box. Ctrl-click or Shift-click adds a part to the selection or takes it out. Ctrl+A selects everything.
Place a part by dragging its card from the Component Toolbox into the 3D view. Double-clicking a card, or choosing Add to Design from its right-click menu, places it in the middle of the view instead.
Move a part with the Placement tool: press on it and drag it across the bench and the boards. Hold Ctrl to snap its pins into the holes underneath, and Shift to line it up with the surface.
Move precisely with the Translate and Rotate tools in the 3D view’s toolbar. Hold Ctrl to snap to 10 mm or 15°, and Ctrl+Shift for 1 mm or 5°. Or type Position (mm) and Rotation (°) in the inspector.
Delete the selection with the Delete key (fn+Delete on a Mac laptop). Backspace doesn’t delete.

Right-click a part for more: View Information… about it, Edit it in the component editor, and Display Connections or Show Connection Names to see its pins. A wire also offers Enter Wiring Mode, and a two-lead part with a polarity, such as an LED or a diode, offers Flip Polarity.

Undo, copy and paste

Action	Keys
Undo	Ctrl+Z
Redo	Ctrl+Y
Cut, copy, paste	Ctrl+X, Ctrl+C, Ctrl+V
Duplicate in place	Ctrl+D
Paste Special	Ctrl+Shift+V

On macOS, use Cmd instead of Ctrl. Each tab keeps its own last 50 steps of undo. Ctrl+V pastes in the middle of the view; Paste on the right-click menu pastes where you clicked.

Paste Special makes a row or a grid of copies, such as a line of LEDs or a bank of resistors. Copy one part, open Paste Special, set the Offset (mm) between copies and the number of Iterations in each direction, and press Apply.

Saving and opening

Save saves the circuit. The first time, it asks where, like Save As….
Save As… saves a copy under a new name.
Open… opens a saved circuit in the current tab. CRUMB asks first if the tab has unsaved changes.
New Circuit Design on the ribbon clears the current tab for a new circuit.

A circuit file is small and can be sent to anyone with CRUMB. It doesn’t contain the parts themselves: it refers to each one by its permanent part ID.

Built-in parts are in everyone’s copy of CRUMB.
Workshop parts are downloaded automatically when the circuit opens. See The Workshop.
Parts you made yourself need sharing too, through the Workshop or by exporting them. Otherwise they appear as red boxes on the other computer.

Microcontroller sketches, audio clips and every setting in the inspector are saved inside the circuit. The one thing never saved is a value from your private headers, such as a Wi-Fi password: if one turns up anywhere in the circuit, it’s left out, and the Output Log lists what was left out.

Running the simulation

The SIMULATION tab runs the circuit.

Run Simulation starts it. The button then reads Pause Simulation, and Resume Simulation while paused.
Reset State switches everything off and puts the bench back as saved. Parts return to their places, and every chip powers up fresh with what’s in its EEPROM and flash kept.
The electrical rate is how many times a second the circuit is solved, from 1 kHz to 1 MHz. The default, 100 kHz, suits most circuits. Raise it for fast signals; lower it if a big circuit can’t keep up.
Under it, the status line shows the rate actually reached and how that compares with real time: 1.00x means the circuit runs at real speed.
The physics rate does the same for the mechanical world. See Physics.

Settings ▼ has two pacing options, and the physics step settings:

Unthrottled runs the circuit as fast as your computer can, instead of in real time. Good for a slow process you want to see the end of.
Auto Throttle lowers the electrical rate by itself when your computer can’t keep up with real time, so simulated time stays continuous and the sound has no gaps. It raises the rate again when there’s room.

A run with either pacing option on isn’t exactly repeatable: the same circuit can come out slightly differently each time.

Switching to another tab pauses the circuit that was running.