# Design a Layered ASCII Canvas Command Processor Design a program for a fixed `10 x 6` ASCII canvas with layered filled rectangles. Commands draw a new frontmost rectangle, erase an area permanently from every rectangle, drag the topmost visible rectangle selected at a coordinate while preserving its layer, bring a selected rectangle to the front, and print the canvas. Erased cells move with their rectangle during drag. ### Constraints & Assumptions - Selection always uses the topmost visible, non-erased cell. - Commands outside the canvas must have a defined validation policy. ### Clarifying Questions to Ask - Does clipping apply when a rectangle is dragged partly outside the canvas? - What character represents an empty cell and how is a rectangle's character supplied? ### What a Strong Answer Covers - Layer ordering, stable rectangle identity, and per-shape erased-cell state. - Coordinate translation during drag and visibility-based selection. - Rendering complexity and tests for overlapping, erased, and moved shapes. ### Follow-up Questions - How would you implement undo without copying the canvas each time? - How would sparse storage change the design for a huge canvas?