#include "FastLED.h"

#define PIN_SLIDE_POT_A0 A0 // input pin of the slide pot
#define PIN_SLIDE_POT_A1 A1 // input pin of the slide pot
#define MAX_SLIDE1_POT_ANALGOG_READ_VALUE 700 // maximum voltage as analog-to-digital converted value, depends on the voltage level of the VCC pin. Examples: 5V = 1023; 3.3V ~700
#define MAX_SLIDE2_POT_ANALGOG_READ_VALUE 700 // maximum voltage as analog-to-digital converted value, depends on the voltage level of the VCC pin. Examples: 5V = 1023; 3.3V ~700

#define NUM_LEDS1 10 // add number of LEDs of your RGB LED strip
#define NUM_LEDS2 10 // add number of LEDs of your RGB LED strip
#define PIN_LED1 3 // digital output PIN that is connected to DIN of the RGB LED strip
#define PIN_LED2 4
#define LED_COLOR CRGB::DarkOrchid // see https://github.com/FastLED/FastLED/wiki/Pixel-reference for a full list, e.g. CRGB::AliceBlue, CRGB::Amethyst, CRGB::AntiqueWhite...

CRGB rgb_led1[NUM_LEDS1]; // color array of the LED RGB strip
CRGB rgb_led2[NUM_LEDS2]; // color array of the LED RGB strip

void setup() {
  Serial.begin(9600);

  pinMode(PIN_SLIDE_POT_A0, INPUT);
  pinMode(PIN_SLIDE_POT_A1, INPUT);
  FastLED.addLeds<WS2812B, PIN_LED1>(rgb_led1, NUM_LEDS1);
  FastLED.addLeds<WS2812B, PIN_LED2>(rgb_led2, NUM_LEDS2);

  Serial.println("Setup done.");
 }

void loop() {
  // 1) Analog value of slide pot is read
  int value_slide_pot_a0 = analogRead(PIN_SLIDE_POT_A0);
  Serial.print("Slide 1 Pot value: ");
  Serial.println(value_slide_pot_a0);
  int value_slide_pot_a1 = analogRead(PIN_SLIDE_POT_A1);
  Serial.print("Slide 2 Pot value: ");
  Serial.println(value_slide_pot_a1);

  // 2) Analog value is mapped from slide pot range (analog input value) to led range (number of LEDs)
  int num_leds1_switchedon = map(value_slide_pot_a0, 0, MAX_SLIDE1_POT_ANALGOG_READ_VALUE, 0, NUM_LEDS1);
  int num_leds2_switchedon = map(value_slide_pot_a1, 0, MAX_SLIDE2_POT_ANALGOG_READ_VALUE, 0, NUM_LEDS2);

   // 3) Light up the LEDs
  // Only LEDs are switched on which correspond to the area left of the slide knob
  for (int i = 0; i < num_leds1_switchedon; ++i) {
    rgb_led1[i] = LED_COLOR;
  }
  // LEDs are switched off which correspond to the area right of the slide knob
  for (int i = num_leds1_switchedon; i < NUM_LEDS1; ++i) {
    rgb_led1[i] = CRGB::Black;
  }
  // Only LEDs are switched on which correspond to the area left of the slide knob
  for (int i = 0; i < num_leds2_switchedon; ++i) {
    rgb_led2[i] = LED_COLOR;
  }
  // LEDs are switched off which correspond to the area right of the slide knob
  for (int i = num_leds2_switchedon; i < NUM_LEDS2; ++i) {
    rgb_led2[i] = CRGB::Black;
  }
  FastLED.show();
}