# Lessons and supplementary material

If this is your first visit, start with [K0 · Why system identification matters](k0/index.md), read [K1 · System identification fundamentals](k1/index.md), then continue to [L0 · Estimate joint inertia and damping](l0/index.md).

Once those ideas are familiar, continue to [L1 · Actuator delay and friction](l1/index.md). Each lesson brings its explanation, evidence status, exercises, and conclusions together on one page; a video appears only when its named teaching question is marked available.

L1 now includes a second isolated actuator experiment on friction versus viscous damping, delivered through the same lesson page with a local CPU report and notebook.

## Find a lesson

The [course directory](../course/index.html#tracks) shows knowledge lessons, synthetic experiments, and hardware experiments. Formal pages now cover K0–K8, L0, L0-E, L1, L1-O, L1-S, and L2–L6. The course map distinguishes Concept, Runnable, and Design draft; numerical reports and simulator evidence are linked only where they exist. Hardware lessons remain marked “Coming later”.

## Explore an experiment

The [L0 supplementary material](l0/README.md) and [L1 supplementary material](l1/README.md) provide focused notes, reports, notebooks, and local apps.

## Discuss the curriculum

[Project resources](../course/resources.md) collects the curriculum design, editorial principles, production process, and implementation progress. Read the [editorial principles](course-editorial-principles.md) before reviewing lesson voice, evidence status, or exercises. The curriculum design is available in [English](course-design.md) and [中文](course-design.zh-CN.md). Reference a lesson code or section D01–D08 when giving feedback.