Highlight

Highlight is a drawing tool you can use during demonstrations to emphasize a certain area on your screen.

Draw freehand or combine your mouse movements with a series of keys to get various geometric shapes: rectangles, circles, lines, etc.

The possible key combinations include:
-Press Shift to draw a rectangle.
-Press Alt to draw a circle.
-Press Control to draw a line.
-Press Control Shift to draw horizontal or vertical lines.
-Press Delete to erase the latest shape drawn.
-Press Apple K to clear the screen.

In the options panel on Highlights you can set the width and color of the brush, as well as show or hide a panel displaying the active drawing mode.