int led1 = D0;
int led2 = D6;
int led3 = D7;
int potenciometer = A2;

int brightness;   // variable for brightness of LED1

void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
  pinMode(potenciometer, INPUT);
}

void loop() {
  brightness = analogRead(potenciometer) / 4; //analogRead for values from 0-1024 and analogWrite from 0-255
  // Because the ADC converter (analogRead) is a ten-bit device, and the PWM timer (analogWrite) is eight-bit. So, 1024/4 = 256
  
  // Set the brightness for each LED based on the scaled potentiometer value
  if (brightness >= 0 && brightness <= 85) {
    analogWrite(led1, brightness);
    digitalWrite(led2, LOW);
    digitalWrite(led3, LOW);
  } 
  else if (brightness > 85 && brightness <= 170) {
    digitalWrite(led1, HIGH); //Remember digitalWrite for HIGH and LOW, and analogWrite for values from 0-255
    analogWrite(led2, brightness - 85); //It´s important to return to the 0 value to gradually turn on the LED
    digitalWrite(led3, LOW);
  } 
  else if (brightness > 170 && brightness <= 255) {
    digitalWrite(led1, HIGH); 
    digitalWrite(led2, HIGH);
    analogWrite(led3, brightness - 170); //It´s important to return to the 0 value to gradually turn on the LED
  }
}