# @nebula/core-navigation Focus management and spatial navigation primitives for controller-first UIs. ## What it does - Calculates spatial relationships between focusable rectangles. - Filters candidates by direction (up/down/left/right). - Picks the best next focus target using a weighted distance heuristic. ## Key concepts - **Rect**: A focusable element described by `x`, `y`, `width`, `height`, and `id`. - **Direction**: The requested movement direction (up/down/left/right). ## Typical use cases - D-pad or stick navigation across grids and lists. - Consistent focus movement in TV or handheld UIs. - Simple focus logic without a framework dependency.