Tail effect for hacked Christmas lights

tail.ino

/*
  G35: An Arduino library for GE Color Effects G-35 holiday lights.
  Copyright © 2011 The G35 Authors. Use, modification, and distribution are
  subject to the BSD license as described in the accompanying LICENSE file.
*/

#include <G35String.h>

#define LIGHT_COUNT (25)
#define G35_PIN (13)

G35String lights(G35_PIN, LIGHT_COUNT);

byte one = 0x7F;
byte two = 0x64;
byte three= 0x20;
char colorArray[12] = {COLOR_WHITE, COLOR_RED, COLOR_GREEN, COLOR_CYAN, COLOR_MAGENTA, COLOR_YELLOW, COLOR_PURPLE, COLOR_ORANGE, COLOR_PALE_ORANGE, COLOR_WARMWHITE, COLOR_INDIGO, COLOR_VIOLET};    
int num = 0;

void setup() {
  lights.fill_color(0, LIGHT_COUNT, 0, COLOR_BLUE);
  lights.fill_color(0, LIGHT_COUNT,  G35::MAX_INTENSITY, COLOR_BLUE);
  delay(1000);
}

void loop() {
  
  num = random(0,12);
  
  for(int i=1; i<25; i=i+1) {
      lights.fill_color(i, 1, G35::MAX_INTENSITY, colorArray[num]);
      if(i>1) {
        lights.fill_color(i-1, 1, two, colorArray[num]);
      }
      if(i > 2) {
        lights.fill_color(i-2, 1, three, colorArray[num]);
      }
      delay(50);
      lights.fill_color(i, 1, two, colorArray[num]);
      lights.fill_color(i-1, 1, three, colorArray[num]);
      lights.fill_color(i-2, 1, 0, colorArray[num]);
  }
  
    //reverse direction
    
  num = random(0,12);
  
  for(int i=23; i>-1; i=i-1) {
      lights.fill_color(i, 1, G35::MAX_INTENSITY, colorArray[num]);
      if(i < 23) {
        lights.fill_color(i+1, 1, two, colorArray[num]);
      }
      if(i <22) {
        lights.fill_color(i+2, 1, three, colorArray[num]);
      }
      delay(50);
      lights.fill_color(i, 1, two, colorArray[num]);
      if(i < 24) {
        lights.fill_color(i+1, 1, three, colorArray[num]);
      }
      if(i < 23) {
        lights.fill_color(i+2, 1, 0, colorArray[num]);
      }
  }
  
  
 
  
}