#include <FastLED.h>

// the whole strip
#define NUM_LEDS 9

#define LED_PIN 6

CRGB leds[NUM_LEDS];

// Define the indexes of the first and last 3 indexes of a 9 pixel strip
bool customLeds[9] = {1, 1, 1, 0, 0, 0, 1, 1, 1};

// Number of Leds that need addressing in the above array
int customLeds_num = 6;

// My Palette
DEFINE_GRADIENT_PALETTE (heatmap) {
  0, 255, 0, 0,      // Red
  128, 0, 255, 0,    // Green
  255, 0, 0, 255     // Blue
};

DEFINE_GRADIENT_PALETTE (heatmap2) {
  0, 0, 255, 255,      // Cyan
  128, 255, 0, 255,    // Magenta
  255, 255, 255, 0     // Yellow
};

CRGBPalette16 myPalette1 = heatmap;
CRGBPalette16 myPalette2 = heatmap2;

void setup() {
  FastLED.addLeds<WS2812B, LED_PIN, GRB>(leds, NUM_LEDS);
  FastLED.setBrightness(20);
  Serial.begin(9600);
}

void loop() {

  uint8_t hue = 0;
  FastLED.clear();

  //  Keep track of how many Leds have been lit
  int customLedIndex1 = 0;
  int customLedIndex2 = 0;

  for (int i = 0; i < NUM_LEDS; i++) {
    // Each i led get the correct color given their place in the array  - 0, 51, 102, 153, 204, 255

    //lights a speficic pixel only if it's in the customLeds truth table
    if (customLeds[i]) {
      // works out where on the gradient a specific pixel is
      hue = (customLedIndex1 * (255 / (customLeds_num - 1)));

      //I'm sure the trouble lies in this bit of code
      leds[i] = ColorFromPalette(myPalette1, hue , 255, LINEARBLEND);

      // Output to check the value...which seem to check out
      Serial.print(customLedIndex1);
      Serial.println(hue);

      //increments the index for the next pixels value on the gradient
      customLedIndex1++;

    }
  }
  FastLED.show();
  customLedIndex1 = 0;

}