Объемная бумажная модель математических символов

A 2x2 grid of 4 large mathematical symbols built as pop-up paper engineering on an opened book [Top Left: The Integral (∫) as a towering paper archway, cut-paper strata, printed equations as microtext wallpaper] [Top Right: The Sigma (Σ) as a folded paper museum with sharp origami cantilevers, shadow play, diagram callouts] [Bottom Left: The Pi (π) as a pop-up classical gate in layered cardstock, weathered ink textures, tiny paper pedestrians] [Bottom Right: The Klein bottle silhouette as an impossible pop-up sculpture, paper tabs and join lines visible, elegant paradox geometry] Tabletop editorial lighting, shallow DOF, crisp paper fibers, bookbinding details, inked diagrams, swiss grid layout, hyper-clean miniature realism.