feat(main): Refined particle graphic and movement
feat(main): Refined particle graphic and movement

Modified the canvas drawing commands used in the refCanvas particle
prototype to a smaller size, different color, with an initial attempt at
shadow "glow". Altered the direction change behavior:

  * only cardinal directions (l, r, u, d)
  * only change to a neighboring dir (e.g. l can go l,  u or d, but not r)
  * max 2 dir changes instead of 1

szurcher/szcom-js