Use the pen
Select Pen to draw on the canvas. Choose Pen Color and thickness before drawing; the color control is contextual, so pen color is different from text color. Selecting the active pen again unequips it and returns you to normal interaction.
Erase or remove a drawing
Select Eraser to remove strokes using the canvas, then toggle it off when finished. A drawing's context menu provides Delete Drawing for that item. Use Clear page only when you intend to remove the current page's content, including more than one drawing.
Undo and move around
Undo and Redo let you recover recent changes. Zoom and scrolling help you work on a detail without losing the rest of the canvas. Shift + wheel scrolls horizontally; the origin control returns to the main starting area. Zooming the canvas does not change the chosen font size or pen thickness setting.
Sketch identification
The app can display an Identifying sketch state and a description of a drawing for context. Treat the result as an interpretation, not a guaranteed recognition of every line, handwritten word, or diagram. You can add a typed explanation beside the sketch when exact meaning matters.