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

#define PIN 6
#define NUM_PIXELS 8
#define RANDOM_CHANCE 50
#define TOP 75

// Parameter 1 = number of pixels in strip
// Parameter 2 = Arduino pin number (most are valid)
// Parameter 3 = pixel type flags, add together as needed:
//   NEO_KHZ800  800 KHz bitstream (most NeoPixel products w/WS2812 LEDs)
//   NEO_KHZ400  400 KHz (classic 'v1' (not v2) FLORA pixels, WS2811 drivers)
//   NEO_GRB     Pixels are wired for GRB bitstream (most NeoPixel products)
//   NEO_RGB     Pixels are wired for RGB bitstream (v1 FLORA pixels, not v2)
//   NEO_RGBW    Pixels are wired for RGBW bitstream (NeoPixel RGBW products)
Adafruit_NeoPixel strip = Adafruit_NeoPixel(NUM_PIXELS, PIN, NEO_GRB + NEO_KHZ800);

// IMPORTANT: To reduce NeoPixel burnout risk, add 1000 uF capacitor across
// pixel power leads, add 300 - 500 Ohm resistor on first pixel's data input
// and minimize distance between Arduino and first pixel.  Avoid connecting
// on a live circuit...if you must, connect GND first.

int vals[NUM_PIXELS] = {0};

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

 Serial.begin(9600);
  strip.begin();
  strip.show(); // Initialize all pixels to 'off'
}

void loop() {
  for (int i = 0; i < NUM_PIXELS; i++) {
    int col = 0;
    if (vals[i] < 0) {
      //intentionally blank
    } else if (vals[i] == 0) {
      int r = random(RANDOM_CHANCE);
      if (random(r) != 1) {
        vals[i] = -10;
      }
    } else if (vals[i] <= TOP) {
      col = vals[i];
    } else if (vals[i] <= TOP + 10) {
      col = TOP;
    } else if (vals[i] <= TOP * 2 + 10) {
      col = TOP * 2 + 10 - vals[i];
      if (vals[i] == TOP * 2 + 10) {
        vals[i] = -1;
      }
    }
    strip.setPixelColor(i, 0, col, col);
    vals[i]++;
  }
  strip.show();
  delay(20);
}