What is Crystal Methods?
Crystal (Alistair Cockburn) is a family of methods tuned by team size and criticality — Crystal Clear for a colocated handful, heavier variants (Yellow, Orange, Red) as headcount and stakes grow. Its founding insight: process weight should fit the project; people and communication matter more than any practice.
Its fingerprints on wider agile: osmotic communication, frequent delivery, reflective improvement, and personal safety as a team property — Crystal named them before they were fashionable.
Worked example
A six-person team building an internal scheduling tool runs Crystal Clear: one room, monthly delivery, a reflection session each cycle, and almost no written process — osmotic communication carries the rest. When the same company staffs a 30-person medical-device project, it deliberately steps up the Crystal scale: more documentation, verification roles, formal reviews. Same philosophy, different weight — which is the whole Crystal idea.