At phone display size, every pixel is precious. In a paint programme, you can place every pixel exactly where you want it. Visual puns' are handy.
Circles turn into cogwheels and slopes become flights of steps.
You have millions of colours available in a paint programme. Make sure you are working at no more than two. For this sort of work you need a graphics pen. If you're still mouse-bound, get yourself a stylus. You'll wonder how you ever managed without it.