The interface

One screen does the work: a 3D view of your build plate, with panels around it. Nothing is hidden behind menus.

┌──────────────┬─────────────────────────────────────┬──────────────┐
│              │            viewport cube            │  G-code      │
│   Settings   │                                     │  inspector   │
│    panel     │           3D build plate            │              │
│              │                                     │  Objects     │
│  Printer     │                                     │  on the      │
│  Filament    │          ┌───────────────┐          │  plate       │
│  Process     │          │  tool cluster │          │              │
│              │          └───────────────┘          │  ▸ Slice     │
└──────────────┴─────────────────────────────────────┴──────────────┘

That's the layout on a computer. A tablet gets the same one with the side panels folded down so the plate stays the biggest thing on screen — see On a tablet. A phone gets the same tools in a one-handed arrangement — see On a phone.

The 3D view

The bed, the print volume, and your models. Navigate it the way you'd expect:

• Drag to orbit, scroll to zoom, right-drag (or two fingers on a trackpad) to pan.
• Click a model to select it, Esc to deselect, Ctrl/⌘ + A to select all.
• Ctrl/⌘ or Shift + click adds to the selection. On a touch screen use the Multi-select tool instead — see Working the plate with a finger or a pen.
• Right-click (or press and hold on a touch screen) a model for duplicate, drop to floor, centre and remove, without leaving the plate. On empty bed you get the plate-wide actions instead.
• The viewport cube top-right snaps the camera to a face, edge or corner. Click its centre to return home.
• Shift + Space switches between perspective and orthographic. Orthographic is the honest one when you're checking whether something is square.

On a trackpad or tablet, a two-finger swipe orbits by default. If you'd rather it panned, change it in Settings → General → Controls. Palm rejection is on by default for pen input.

On a touchscreen, two fingers pinch to zoom and slide to pan — both at once, as you'd expect. Twisting rotates the view, but only if you clearly mean it: once you've started pinching, the view won't tip just because your wrist turned. Rest your hand on the glass while drawing with a pencil and it's ignored.

The tool cluster

Floating under the model, this is where you manipulate what's on the plate.

Tool	Key	What it does
Select & move	M	Drag handles to move; also plain selection
Rotate	R	Spin around an axis
Scale	S	Resize, uniformly or per axis
Pull to floor	F	Click a face; that face becomes the bottom
Multi-select		Touch screens only — each tap adds or removes
Place objects	A	Auto-arrange everything on the bed
Add a model		Same as dropping a file in
Gravity	G	Objects drop to the floor after every move
Model / preview	P	Switch between the model and the sliced G-code

Picking a tool opens a small card beneath it with numeric fields — exact position, rotation in degrees, size in millimetres or percent. Type a number if dragging isn't precise enough.

The plate-editing tools disappear in G-code preview. There's nothing to edit there, and a change you can't see happen is worse than no change.

The settings panel (left)

Three tabs — Printer, Filament, Process — each with a profile dropdown at the top and collapsible groups of options below.

Ctrl/⌘ + F jumps to the search box. Type "infill", "seam", "brim" and the groups filter down. This is usually faster than remembering which tab something lives in.

Full tour: Print settings.

The objects panel (right)

Every model on the plate, with its triangle count and size. Select from here when the 3D view gets crowded.

Watch for the warning badges: outside the build area, and overlaps another object. Both are warnings, not blocks — you can still slice, but you probably shouldn't.

Each row also has Duplicate and Remove. Remove asks once ("Click again to remove") before it does anything.

On a touch screen the panel starts folded to a chip with the object count, because it sits on top of the plate it describes and a finger can't hover it out of the way. Tap the chip to unfold it; it stays however you leave it. A warning triangle appears on the folded chip if something can't print where it sits.

The slice button (bottom right)

Press Slice. Afterwards it becomes Re-Slice, and turns amber when you've changed something since the last slice — so a stale preview always looks stale.

Below it, a status line: Ready to slice → Slicing… → Sliced · N layers · 1h 12m, or a red failure with the reason.

Once it succeeds, the result button lets you Download, Just upload, or Upload & print. It remembers which you used last.

The G-code inspector (right, after slicing)

Appears when you switch to preview. Colour the toolpaths by role, speed, temperature and more; hide path types you don't care about; scrub through layers and through individual moves. See Reading the preview.

Tap its G-code header to fold it away when the legend is in front of what you're trying to see — the layer counter stays, the Slice button stays put, and the slicer remembers what you chose.

Notifications

Messages appear bottom-left — top of the screen on a phone, where the sheet isn't. Info and success fade after a few seconds; errors stay until you dismiss them. Longer jobs get a progress strip at the top that turns into a notification when it's done.

Moving between Home, Slice and Settings

When you first open the app it shows the Cold Crabby logo with a progress bar beneath it. The logo appears immediately as a soft, low-detail version and sharpens a moment later once the full artwork has downloaded. The bar follows the real download, so it tells you how much is genuinely left.

The rail on the left switches between the three areas. The app loads each one the first time you open it, so on a slow connection the first visit can take a moment.

When it does, you'll see it: a thin amber line runs along the top of the work area, and the rail item you're heading to shows a spinner. Nothing appears for a switch that's already instant — which is most of them, because the app quietly fetches the other areas in the background once it's finished starting up.

If the app was updated while your tab stayed open, a part it hasn't loaded yet may have already been replaced on the server. Rather than failing silently, it offers you a Reload banner. Take it — a reloaded tab is a consistent one.

Undo

Ctrl/⌘ + Z undoes, Ctrl/⌘ + Y (or ⌘ + Shift + Z) redoes. This covers what you do to the plate — moving, rotating, scaling, adding, deleting, arranging.

On a touch device without a keyboard, undo and redo buttons appear in the 3D view toolbar so you can step through history without a shortcut. They show up automatically on touch tablets and phones; force them on or off any device in Settings → General → Controls.

Settings and profile edits are not undoable. They're saved deliberately, and changing a value back is the undo.

Making it yours

Settings → Appearance has light / dark / system, and an accent colour: the default molten amber, five other presets, a custom colour, or — on macOS and Windows — whatever your system accent is set to.

Settings → General has the graphics knobs: field of view, anti-aliasing, render resolution and preview detail. Turn them down on a weak GPU, up on a good one.

On a tablet

An iPad has the screen for the full layout but not the mouse, so two things change: everything is bigger, and nothing that floats over the plate stays open on its own.

• Panels start folded. The G-code inspector and the objects list each show just a header — G-code · 42 / 180, Objects 2. Tap a header to open it, tap again to fold. Your choice sticks from then on.
• Print settings are a drawer, reached from the tab on the left edge just below the toolbar. Tap it to open, tap outside to close. It's out of the middle of the screen on purpose: that's where your model is, and the plate stays visible behind the drawer rather than being dimmed out.
• Panels use the room they have. Unfolded, the G-code inspector shows its whole legend and both sliders without scrolling.
• Everything is finger-sized. Buttons, dropdowns, the layer slider and the legend chips are all sized for a fingertip rather than a cursor.

Split View and Slide Over shrink the window, and the layout follows: below about 1024 points wide you get the folded arrangement on any device, including a narrow window on a desktop.

Working the plate with a finger or a pen

• Tap a model to select it. Tapping is judged generously: a fingertip is a wide, soft target that never lands and lifts on the same pixel, so a tap still counts as a tap even when it slides a little. Tap empty bed to deselect.
• Multi-select, in the tool cluster, is the stand-in for holding ⌘/Ctrl. Turn it on and each tap adds an object to the selection or takes it back out; turn it off to go back to one-at-a-time. It appears once there are at least two objects to choose between, and only where there's no modifier key to hold.
• Press and hold a model for the same menu a right-click gives: duplicate, drop to floor, centre, remove — acting on the whole selection if you have one. Hold on empty bed for select all, clear, place objects and reset view.
• Drag a selected model to slide it across the bed. Select it first, then drag: one deliberate tap means nothing gets shoved out of place by a stray swipe. Dragging anywhere else still orbits the camera, and the move handles are drawn larger so a fingertip can pick one axis rather than all three.
• Palm rejection is on by default. While a pen is in use, the hand resting on the glass is ignored, so the view doesn't lurch mid-stroke. Turn it off in Settings → General → Controls if you never use a stylus.

Two fingers pinch to zoom, drag to pan and twist to roll, anywhere on the plate.

On a phone

The same app, rearranged for one hand. There is no separate mobile version and nothing to install — open the slicer's address in your phone's browser.

┌─────────────────────────────┐
│ 🦀  My plate              ● │  ← title bar
├─────────────────────────────┤
│        [ tools ]            │
│                             │
│                             │
│         3D plate            │
│                             │
│                  Objects 2  │
│  ┌───────────────────────┐  │
│  │ model.stl     ▸ Slice │  │  ← slice sheet
│  └───────────────────────┘  │
├─────────────────────────────┤
│  Home      Slice    Settings│  ← tab bar
└─────────────────────────────┘

• Navigation moves to the bottom, where your thumb already is.
• Slice lives in a sheet across the bottom of the plate, with the file name and the download / send buttons beside it. After slicing, the G-code inspector opens inside that sheet and scrolls — Slice stays put.
• Print settings are a drawer. Pull the tab on the left edge, or tap it. Tap anywhere outside to close.
• The objects list is folded to a chip showing how many models are on the plate. Tap it to open the list; a warning triangle appears on the chip if something can't print where it sits, so a folded list never hides a problem.

Two things are left out rather than squeezed in: the viewport cube (drag it with what?) and the projection toggle. Reset-view — the house icon — still frames the plate in one tap, and both come back the moment you open the slicer on something wider. Everything that actually gets a model sliced is there.

Turned sideways, the chrome shrinks to give the plate the height back: the tab bar drops its labels and the panels get shorter.