Neon graffiti
One thick ribbon whips around a dark field, its body striped by concentric outlines and a rainbow that slides along its length.
A single tube-like stroke loops and folds across the canvas like a bent neon sign, continuously re-shaped as it swings between two anchor points. Bands of colour run along the ribbon and around its edge, cycling through the spectrum while the whole figure sweeps and doubles back on itself.
The ribbon is not a curve at all: hundreds of discs are placed along a straight line between the anchors, then displaced by stacked sine and cosine offsets, and the stroke is simply their union. Several passes redraw the trail at shrinking radii, which is what produces the concentric outline stripes. All the discs land in one instanced GPU draw with the rainbow computed in the shader, so the per-frame cost stays flat however long the ribbon gets.
