{"id":"top-projection-counts-nonzero-cells","text":"The xy (top-down) projection area equals the count of cells where `grid[i][j] > 0`, not the sum of cell values — each non-empty stack casts exactly one unit square","truth_value":"IN","source":"entries/2026/06/06/projection-area-of-3d-shapes-solution.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{},"created_at":"","updated_at":"","reviewed_at":"","verified_at":"","retracted_at":"","explanation":{"steps":[{"node":"top-projection-counts-nonzero-cells","truth_value":"IN","reason":"premise"}]}}