Yeah, looks like the runner is referencing a global planeMatrix1. Copying an example into your code will work, but a cleaner workaround is to make your solution pure and only adapt at the boundary:

// your actual solution
function countPlanes(matrix) {
  // ... implement logic here
  return 0;
}

// glue for the buggy runner
const mat =
  (typeof globalThis !== 'undefined' && 'planeMatrix1' in globalThis)
    ? globalThis.planeMatrix1
    : /* your local test data here */ [];

console.log(countPlanes(mat));

Key points:
- Don’t reference planeMatrix1 directly or in default params; accessing an undeclared identifier throws.
- Use globalThis lookup to avoid ReferenceError.
- Keep your logic testable by taking matrix as a parameter.
- Also worth reporting the challenge bug so they fix the harness.