#include <Adafruit_NeoPixel.h>

void HSVtoRGB(float H, float S,float V,int &R, int &G, int &B){
    while(H>360) H-=360;
    if(H>360 || H<0 || S>100 || S<0 || V>100 || V<0){
        return;
    }
    float s = S/100;
    float v = V/100;
    float C = s*v;
    float X = C*(1-abs(fmod(H/60.0, 2)-1));
    float m = v-C;
    float r,g,b;
    if(H >= 0 && H < 60){
        r = C,g = X,b = 0;
    }
    else if(H >= 60 && H < 120){
        r = X,g = C,b = 0;
    }
    else if(H >= 120 && H < 180){
        r = 0,g = C,b = X;
    }
    else if(H >= 180 && H < 240){
        r = 0,g = X,b = C;
    }
    else if(H >= 240 && H < 300){
        r = X,g = 0,b = C;
    }
    else{
        r = C,g = 0,b = X;
    }
    R = (r+m)*255;
    G = (g+m)*255;
    B = (b+m)*255;
}



#define PIN            0
#define NUMPIXELS      25 // 24
#define CENTER 12.5
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);
double hue = 0.0;
 void setup() {                
   pixels.begin();
   pinMode(1, OUTPUT); //LED on Model A   
   pinMode(PIN, OUTPUT); //LED on Model A   
  digitalWrite(1, HIGH);
    delay(500);
   digitalWrite(1, LOW);
 }

 // the loop routine runs over and over again forever:
 void loop() {
    
   for(int i=0;i<NUMPIXELS;i++){
    int r,g,b;
    int hueOffset = (abs(CENTER-i)/(float)CENTER) * 75;
    HSVtoRGB(hue + hueOffset, 100, 15,r,g,b);   
    pixels.setPixelColor(i, pixels.Color(r,g,b)); // Moderately bright green color.
   }
   hue += 0.5;
   if(hue>=360) {
    hue -= 360;
   }
     pixels.show(); // This sends the updated pixel color to the hardware.
    delay(15); // Delay for a period of time (in milliseconds).
  }