↩ 🔵 🔵 🔵 ❪✺₄❫ Physical Sets ○ ❪✺_❫ Physical Subs ○ ❪✺_ₛₛ₀❫ Subset Portals ○ ❪✺_ₛₛ❫ Astronomical Subsets ○ ❪✺_ₛₛ❫ Electromagnetic Subsets ○ ❪✺_ₛₛ❫ Mechanical Subsets ○ ❪✺_ₜₛ❫ Physical Typesets ○