The pixel pencil is a hard-edge square brush. The default shortcut for this tool is N.
There are some basic brush settings that you can change in your panel under the color wheel.
Clicking the gear icon, you have Simple, Advanced, and Full settings modes. Below is what's available in Full mode.
The different settings and characteristics include:
Size: makes the pencil tool bigger
Tap the box next to the slider to make the size respond to pressure;
Minimum Size: while pressure for size is active, the pencil will not go smaller than this percentage of the max size;
Size Jitter: creates variation in the size of your pencil shape stamps. Higher value leads to higher variation;
Flow: formally the density setting. The controls the opacity of each stamp of the pencil shape. Tap the box next to the slider to make this setting respond to pressure.
Opacity: sets the opacity for each stroke of the brush or pencil. Lower value makes it more transparent;
Stabilizer: stabilizes your brush strokes.
These are explained in more detail on our Brush page or view our video guide: