Teaching through level design
Also said as Show, don't tell, Silent tutorial, World 1-1
Arranging the first spaces so that the player works out the rules by bumping into them, safely, with no text. The obstacle comes first, in a place where failing costs nothing, and the lesson arrives as an idea of their own.
People skip instructions and remember what they worked out for themselves. A level that teaches also respects the player, who gets to feel clever rather than instructed.
Say it
“Before the first pit, put a wall one jump high with no danger around it, so they can only get past by pressing jump. Then the pit is a test of something they already know.”
Where you’ve seen it
Super Mario Bros. opens with empty ground, then a Goomba walking at you, then blocks above your head. Miyamoto and Tezuka have explained that World 1-1 was built so players could gradually and naturally understand what they were doing.
Not to be confused with tutorial
A tutorial explains the rule and then asks you to do it. Teaching through the level asks you to do it, and you only find out afterwards that you learned a rule.