Here's the whole idea in one breath: a mark on the page isn't just a smudge of pencil — it carries a feeling of the thing it stands for. A few quick jagged lines and your brain shouts "spiky"; a row of soft horizontal strokes and it murmurs "calm water". You're not drawing the object at all. You're drawing the trace of a movement, and the viewer's eye fills in the rest.
Start with Something You've Already Done
Think about how you'd doodle the sea in the margin of your book. You wouldn't paint every drop — you'd flick a few wavy horizontal lines and everyone would know exactly what you meant. That's the whole trick, and you've been doing it since you could hold a crayon. A mark is visual shorthand: the fastest possible way to say "rough", "soft", "wet" or "old" without spelling it out. Artists just do it on purpose, and with more control.
And here's the sneaky bit — the gesture you make leaves its energy in the mark. A line scratched out fast and hard looks tense and electric. The same line laid down slow and gentle looks sleepy. Your hand's mood ends up on the page whether you mean it to or not, so you may as well aim it. A weathered rock wants a dry, scratchy, broken line, because that's what making a dry scratchy line feels like. The doing and the meaning are the same thing.
The Two Ideas That Do All the Work
The first is shorthand: one well-chosen mark can stand in for a thousand of the real things. Dots for a sandy beach, short flicks for grass, soft smears for distant hills. You're trusting the viewer's eye to do the joining-up, and it always does.
The second is gesture: how you make the mark — fast or slow, hard or soft, wet or dry — is half the message. Same pencil, same hand, completely different feeling depending on the speed and pressure.
In the toy, you'll see that none of the four patches actually look like water or bark up close — they're just scribbles, strokes, dots and scratches. But drop them next to the right label and suddenly they click into place. That click is your eye reading shorthand, and it's the foundation of everything else in this concept.