The interface
Scissor fills the browser window with one editing surface: a menu bar and a control bar across the top, the tool palette down the left, the canvas in the middle with the panel dock beside it, and a status bar along the foot. Everything runs on your own machine, so a document stays where you put it.
Shortcuts here are written in the macOS form. On Windows and Linux, read ⌘ as Ctrl and ⌥ as Alt; ⇧ is Shift and ⌃ is Control.
The menu bar
Nine menus run along the top: File, Edit, Object, Type, Select, Effect, View, Window and Help. A tick beside an item means the setting is on; an item drawn in grey cannot be used at the moment. The Help menu opens with a search field that finds any command in any menu and shows the path to it, which is quicker than remembering where something lives. At the right of the bar sits a readout of the current document: its name, an asterisk while there are unsaved changes, the zoom percentage, and whether you are in Preview or Outline.
The control bar
The strip under the menu bar changes with what you have selected. It names the selection (Path, Group, Type, No Selection and so on), then gives you the fill and stroke swatches, the stroke weight, the opacity, and the X, Y, W and H of the selection. A live rectangle or polygon gains a corner radius field. Type into any of these fields and press Enter, or leave the field, to apply the value; ↑ and ↓ step it, with ⇧ for ten times the step, and dragging the small label beside a field scrubs the value.
The tool palette
The tools sit in a single column on the left, grouped by what they do and divided by thin rules. A slot with a mark in its lower corner holds more than one tool: hold the button down, or right-click it, to open the flyout and pick another. The tooltip gives the tool's name and its shortcut. Double-clicking a tool that has options opens them. Below the tools are the fill and stroke boxes: X moves between them, ⇧X swaps the two, D returns to the default white fill and black stroke, and / sets the front one to none.
Tabs and the canvas
Open documents appear as tabs above the canvas. A tab shows the document's name with an asterisk while it has unsaved changes; click the tab to switch, or the × to close it. When you enter a group to work inside it, a breadcrumb bar appears under the tabs; click the ‹ or press Esc to step back out.
Below that is the canvas. ⌘R shows the rulers, which measure in the document's units from the top left corner of the active board and carry a marker that follows the pointer. Drag out of a ruler to pull a guide onto the artwork; drop a guide back on a ruler to be rid of it. Hold Space for the Hand tool while you drag, or drag with the middle button. The wheel scrolls, and the wheel with ⌘ or ⌥ held zooms about the pointer. ⌘0 fits the board in the window, ⌥⌘0 fits all of them, and ⌘1 returns to actual size.
Boards and the pasteboard
Boards are what Scissor calls artboards: the white rectangles that hold the artwork you intend to keep. Each carries its name above its top left corner, and the active board is drawn with a stronger frame than the rest. If the document has a bleed, it is drawn around the board as a red dashed rectangle. Add one from Object › Boards › New Board, draw and reshape them with the Board tool (⇧O), and set a board's size and name in Board Options. The Boards panel lists them all, and the status bar has a menu for jumping between them.
The grey surround is the pasteboard. It is part of the document, so you can park a sketch, an offcut or a colour test there and it is saved with the file, but when you export a board only what falls inside that board's rectangle is written out.
The panel dock
Panels live in the column on the right, stacked in groups with a tab for each panel. Open one from the Window menu, where it is ticked while its group is on screen. Click a tab to bring its panel forward. Drag a tab onto another group's tab strip to move it there, or drag it out of the dock to leave it floating over the canvas; drag a group's tab strip to lift the whole group out, and drop it back over the dock to put it home. A floating group can be resized from its bottom right corner. The × at the right of a tab strip closes that group, and Window › Reset Panels puts the whole arrangement back to its starting state. Your layout is remembered between sessions. Tab hides the tool palette, the control bar and the dock so that only the artwork is left; press it again to bring them back.
The status bar
The bar at the foot holds a zoom menu with the usual steps, a menu of the document's boards, the name of the current tool, and, at the right, the action that ⌘Z would undo.
Light and dark
Scissor follows your system setting for light and dark. To fix it one way, choose View › Appearance and pick System, Light or Dark. The choice is remembered, and it carries through to the canvas as well as the panels: the pasteboard, the rulers and the board labels are all drawn to suit the theme you are in.