Bands stack newest on top, so depth is age — the deepest band is permanently the first buy that ever happened on this curve. Nothing is ever removed or reordered.
A buy of 0.004 ETH or more lays one band. Thickness is 6px + 58px × min(1, paid ÷ 0.05 ETH), floored and capped so no single band can swallow the core.
Colour comes from the wallet alone: h = sha256(address), hue 196 + h[1]%24 when h[0] < 64 — a slate seam, about a quarter of wallets — and 16 + h[1]%44 otherwise. Saturation 20 + h[2]%22, lightness 30 + h[3]%30. The same wallet always lays the same colour and anyone can recompute it.
At 500 bands the core is capped. Strata pays nothing. It only remembers the order you arrived in.