Collision effect for hacked Christmas lights

collision.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);

void setup() {
  lights.fill_color(0, LIGHT_COUNT, 0, COLOR_RED);
}

void loop() {
  
  for(int i=1; i<12; i=i+1) {
      lights.fill_color(i, 1, G35::MAX_INTENSITY, COLOR_RED);
      lights.fill_color(24-i, 1, G35::MAX_INTENSITY, COLOR_GREEN);
      delay(100);
      lights.fill_color(i, 1, 0, COLOR_RED);
      lights.fill_color(24-i, 1, 0, COLOR_GREEN);
  }
  
  //collision
  lights.fill_color(0, LIGHT_COUNT, G35::MAX_INTENSITY, COLOR_VIOLET);
  delay(100);
  lights.fill_color(0, LIGHT_COUNT, 0, COLOR_RED);
  
  for(int i=12; i<25; i=i+1) {
      lights.fill_color(i, 1, G35::MAX_INTENSITY, COLOR_RED);
      lights.fill_color(24-i, 1, G35::MAX_INTENSITY, COLOR_GREEN);
      delay(100);
      lights.fill_color(i, 1, 0, COLOR_RED);
      lights.fill_color(24-i, 1, 0, COLOR_GREEN);
  }
  
  //reverse direction
  
  for(int i=23; i>12; i=i-1) {
      lights.fill_color(i, 1, G35::MAX_INTENSITY, COLOR_RED);
      lights.fill_color(24-i, 1, G35::MAX_INTENSITY, COLOR_GREEN);
      delay(100);
      lights.fill_color(i, 1, 0, COLOR_RED);
      lights.fill_color(24-i, 1, 0, COLOR_GREEN);
  }
  
    //collision
    lights.fill_color(0, LIGHT_COUNT, G35::MAX_INTENSITY, COLOR_ORANGE);
    delay(100);
    lights.fill_color(0, LIGHT_COUNT, 0, COLOR_RED);
  
  
  
  for(int i=12; i>-1; i=i-1) {
      lights.fill_color(i, 1, G35::MAX_INTENSITY, COLOR_RED);
      lights.fill_color(24-i, 1, G35::MAX_INTENSITY, COLOR_GREEN);
      delay(100);
      lights.fill_color(i, 1, 0, COLOR_RED);
      lights.fill_color(24-i, 1, 0, COLOR_GREEN);
  }
  

}