(cropped screenshot)

(It'll be animated when it's running)


The Code (teslacoil.r) :


rebol [title: "A Tesla Coil"]

random/seed now

branch: funct[x y L a][
  x2: x + (L * sine a)
  y2: y - (L * cosine a)
  L2: L * (0.4 + ((random 2000) * 0.57 / 2000))
  a2: a + (random 2000 / L) - (random 2000 / L)
  c: to-integer (L * 7)
  if c > 255 [c: 255]
  append block compose [
    line-width (L / 7)
    pen (to-tuple reduce [c c 255])
    line (as-pair x y) (as-pair x2 y2)
  ]
  if L > 8 [loop (random 3) [branch x2 y2 L2 a2]] ; recursive
]

view layout[
  origin 0x0 space 0x0
  b: box black 400x400
  led 0x0 rate 60 [
    block: copy [line-cap rounded]
    branch 200 399 64 0
    b/effect: reduce ['draw block]
    show b
  ]
]