Multi-arm logarithmic vortex

@grid: 1 / 100vw 100vh;

@content: @pattern(
  texture_0 {
    background: linear-gradient(@r(360deg), @stripe.m10.pn(
      #ff1744,#ffea00,#00e5ff,#7c4dff,#ffffff
    ));
  }
  r: length(pos);
  s: 3atan(pos.y, pos.x) + 8log(max(r, .001)) - 1.2t;
  fill: texture(texture_0, .5 + r * vec2(cos(s), sin(s)));
)