In Procreate, you create straight & curved lines & clean shapes such as squares, circles etc by holding at the end of the line/shape for a second…it will automatically create a straight/curved line or shape closest to what you’ve drawn without any wobble to the lines. You can then add a key stroke to also hit to create an exact circle/square etc that measure the same on each side. It saves a lot of time, compared with the straight/curved line in Painter… esp with the shape ability as well. It’s very natural to use as you draw.