#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
  #include <avr/power.h>
  #endif

  #define PIN 2

  Adafruit_NeoPixel strip = Adafruit_NeoPixel(50, PIN, NEO_GRB + NEO_KHZ800);

  void setup() {
    // This is for Trinket 5V 16MHz, you can remove these three lines if you are not using a Trinket
      #if defined (__AVR_ATtiny85__)
          if (F_CPU == 16000000) clock_prescale_set(clock_div_1);
            #endif
              // End of trinket special code
                
                  strip.begin();
                    strip.show(); // Initialize all pixels to 'off'
                    }

                    void loop() {
                      // Just color x LED of the strip with one color
                        //
                          //colorStrip( strip.Color( 0,255,0 ), 144 );
                            //delay( 2000 );
                              //colorStrip( strip.Color( 255,0,0 ), 20 );
                                //delay( 2000 );

                                  // Show a color interpolation between GREEN and RED
                                    // spread it over 144 LEDs
                                      // 
                                        uint32_t green = strip.Color(0,255,0);
                                          uint32_t red   = strip.Color(255,0,0);
                                            uint32_t color = 0;
                                              for( int i=0; i< strip.numPixels(); i++ ){
                                                    color = colorInterpolate( red, green, 144, i );
                                                          strip.setPixelColor( i, color );
                                                            }
                                                              strip.show();
                                                                delay( 5000 );
                                                                  
                                                                  }

                                                                  // Fill x Dots of a given color and turn-off the others
                                                                  void colorStrip( uint32_t color, uint16_t len ) {
                                                                     for( uint16_t i=0; i<len; i++ ){
                                                                            strip.setPixelColor( i, color );
                                                                               }
                                                                                  for( uint16_t i=len; i<strip.numPixels(); i++ ){
                                                                                         strip.setPixelColor( i, 0 ); // black
                                                                                            }
                                                                                               strip.show();
                                                                                               }

                                                                                               // Interpolate a color between 2 other colors
                                                                                               uint32_t colorInterpolate( uint32_t fromColor, uint32_t toColor, uint16_t maxSteps, uint16_t position ){
                                                                                                 // fromColor
                                                                                                   uint8_t r = ( fromColor & ((uint32_t)0xFF << 16) ) >> 16;
                                                                                                     uint8_t g = ( fromColor & ((uint32_t)0xFF << 8) ) >> 8;
                                                                                                       uint8_t b = ( fromColor & ((uint32_t)0xFF) );
                                                                                                         // toColor
                                                                                                           uint8_t r2 = ( toColor & ((uint32_t)0xFF << 16) ) >> 16;
                                                                                                             uint8_t g2 = ( toColor & ((uint32_t)0xFF << 8) ) >> 8;
                                                                                                               uint8_t b2 = ( toColor & ((uint32_t)0xFF) );
                                                                                                                 
                                                                                                                   // Interpolate
                                                                                                                     float ri = r - ( ((float)(r-r2)) /maxSteps * position);
                                                                                                                       float gi = g - ( ((float)(g-g2)) /maxSteps * position);
                                                                                                                         float bi = b - ( ((float)(b-b2)) /maxSteps * position);

                                                                                                                           return strip.Color( (int)ri, (int)gi, (int)bi );
                                                                                                                           }