Impossible Isometric Toy Decades Grid

2x2 grid, 16:9, popular toys of 1850, 1940, 1990, 2026 I(0) = blank matte background. I(1) = final impossible isometric structure of the endless cycle of $ THEME, its looping path forming silhouette $ SHAPE, Escher-style with ambiguous connections that close seamlessly. ∂I/∂t = Δ(I, $ THEME, $ SHAPE) with constraints: isometric projection, impossible-geometry continuity, uniform ambiguous lighting, stage-to-stage flow, silhouette adherence. Integration: t=0.0–0.15: faint silhouette outline and the skeletal path of the loop appear, corners deliberately ambiguous. t=0.15–0.4: the first stages of $ THEME build along the lower run of the path - figures, structures, and props marking the cycle's opening beats. t=0.4–0.7: middle stages populate the ascending and turning sections; the path bends in ways that shouldn't connect but visually do. t=0.7–0.9: the final stages meet the beginning - the path closes on itself in an impossible join, completing the loop and the silhouette. t=0.9–1.0: uniform flat lighting locks the illusion, stage labels and directional arrows appear along the loop, final polish. Output I(1) as an 8K impossible-isometric masterwork.