Pteropixel
Canvas and panels
Every app opens a document on a canvas that fills the window. The toolbar along the bottom opens panels: properties, contents, history, export, settings and the rest.
Panels
Panels float over the canvas. Drag one by its header to move it, and by its edges to resize it. Where you left your panels is remembered for each document.
In Paint and the Font Editor, hold ⇧ while dragging a panel to dock it into the layout beside the canvas instead. Press Escape during a drag to put the panel back where it was. The Music Composer's panels always float.
In the Font Editor an arrangement of panels is a workbench. You can keep several and switch between them with ⌃⌥← and ⌃⌥→. In the Workbench menu at the end of the bottom toolbar, double-click a workbench's name to rename it; duplicate and delete appear on the card under the pointer.
⇧I inverts the colours of the panel you're working in: a dark canvas under a light interface, or the other way round.
Moving around
Zoom with ⌘+ and ⌘-, or pinch on a trackpad. On a touch screen, double-tap to zoom in on that spot. ⌘0 switches between fitting the document to the window and 100%. Hold Space and drag to pan with any tool.
Undo
Every change can be undone with ⌘Z and redone with ⌘⇧Z. The history panel lists each step, and clicking one goes back to it.
Copy and paste
⌘C, ⌘X and ⌘V work between Paint and the Font Editor, and between tabs. A glyph pasted into an artwork lands on the pixel layer the Pencil draws on, in the stroke colour; pixels copied from an artwork paste into a glyph as a selection you can move.
Search
⌘⇧P opens Search, which finds documents and commands by name.
Info
In an Info tab, press a value to copy it.