// A sprinter's silhouette, walked as a dashed path:
// Same leaning, curved figure as before, but instead of solid `fd` moves
// we step along it in `cell`-sized units, sewing only the first `ink`
// fraction of each cell and jumping the rest. Raise `gapratio` and the
// line dissolves into sparser and sparser dashes.
//
//   seg(len, head, cell, gapratio): travel `len` mm along heading `head`,
//   broken into dashes. Each `cell` = one dash + one gap; `gapratio` (0..1)
//   is the gap's share, so ink = cell * (1 - gapratio).
def seg(len, head, cell, gapratio) [
  seth head
  let ink = cell * (1 - gapratio)
  let travelled = 0
  while travelled + cell <= len [
    down  fd ink            // sew the dash
    up    fd cell - ink     // jump the gap
    travelled += cell
  ]
  // finish any remainder so every copy ends at the same height
  let rest = len - travelled
  if rest > 0 [
    down  fd min(rest, ink)
    if rest > ink [ up  fd rest - ink ]
  ]
]

// The runner: five segments swinging around a forward `lean`.
// `cell` and `gapratio` are threaded straight through to every dash.
def runner(lean, cell, gapratio) [
  seg(9,  lean,     cell, gapratio)   // back leg / push-off
  seg(5,  lean - 8, cell, gapratio)   // hip straightens
  seg(12, lean + 6, cell, gapratio)   // torso pitched forward
  seg(6,  lean - 4, cell, gapratio)   // shoulders ease back
  seg(4,  lean + 2, cell, gapratio)   // head
]

seed 3
stitchlen 1.5              // dashes themselves stay finely stitched
bean 3
color 5
home

// Repeat horizontally, each copy dashier than the last:
// --- runner field ---
let count = 20            // [6:1:24] number of runners
let startx = -38
let gapx = 3.5            // [2:0.1:5] spacing between runners, mm
let cell = 2              // [0.8:0.1:4] dash-and-gap period, mm

repeat count [
  let i = repcount - 1                  // 0-based

  // gap-to-line ratio climbs: 0.15 (almost solid) → ~0.87 (mostly gaps)
  let gapratio = 0.1 + i * 0.042

  up  setxy(startx + i * gapx, -18)  down
  runner(16, cell, gapratio)
  trim
]