Two kinds of skill

Every skill in a forest is one of exactly two kinds. The split answers a simple question: is there anything meaningful to grade?

No-level skills (yes/no). Some abilities are small enough that you either know them or you don't. Media queries are the classic example: once you can write them, there's no interesting difference between a "beginner" and an "expert" at media queries. Grading it would be theatre. These skills are a plain checkbox — you hold it or you don't.

Three-level skills. Bigger abilities are worth growing through. These carry three levels — beginner, confident, and expert — and the levels behave like rungs: each one is a prerequisite of the next. You pass through beginner on the way to confident, always. In a tree, each level is treated as its own skill, which is why you'll see names like "React I" and "React II" sitting one above the other.

How to choose the kind when cutting a new skill:

• If progressing through it would take a month or more of real work, it's three-level.
• If there's nothing between "can't" and "can," it's no-level.
• When genuinely unsure, make it three-level — a level that turns out unnecessary is easier to live with than a checkbox hiding real depth.

The next page defines what the three levels actually mean, because the method leans hard on those definitions being concrete.