#include <Servo.h>
#include <Arduino.h>
int pos1 = 0, pos2 = 0;
Servo servo1, servo2;

unsigned long previousMillis_1;
unsigned long previousMillis_2;
const unsigned long interval_1 = 10;
const unsigned long interval_2 = 15;

int dir1 = 1;
int dir2 = 1;

void setup(){
  servo1.attach(3);
  servo2.attach(2);
  servo1.write(pos1);
  servo2.write(pos2);
}

void loop(){
  unsigned long currentMillis = millis();

  if(currentMillis - previousMillis_1 >= interval_1){
    previousMillis_1 = currentMillis;
    if(dir1 > 0){
      pos1 += 1;
      if(pos1 >= 180){
        dir1 = -1;
        pos1 = 180;
      }
    } else{
      pos1 -= 1;
      if(pos1 <= 0){
      dir1 = 1;
      pos1 = 0;
    }
  }
  servo1.write(pos1);
}
  if(currentMillis - previousMillis_2 >= interval_2){
    previousMillis_2 = currentMillis;
    if(dir2 > 0){
      pos2 += 1;
      if(pos2 >= 180){
        dir2 = -1;
        pos2 = 180;
      }
    } else {
      pos2 -= 1;
      if(pos2 <= 0){
        dir2 = 1;
        pos2 = 0;
      }
    }
    servo2.write(pos2);
  }
}