An icosahedral capsid self-assembles: 32 fluorescent capsomer subunits — 12 pentagonal pentons on the five-fold axes, 20 hexons between them — drift in from outside and snap one by one into their symmetric positions on the shell, flashing as they lock, until the T=3 icosahedron is complete; it holds, then disassembles and loops. The pointer rotates the particle, scroll raises the binding energy that speeds assembly and a press drives every subunit home at once.