Hit the flag, and adjust the knobs as you like! Click the eraser to erase everything. Click the switch to hide/show the knobs. Setting "Pen Color Change" to 100 will make it grow near the middle and shrink everywhere else. 99 makes it grow towards the bottom, and 98 makes it grow towards the top. 97 is toward the right, 96 is toward the left.
For @wainglett, a beginner at scratch, and an amazing kid!