int topleft;
int topright;
int downleft;
int downright;
int waittime = 1;

void setup() {
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  TCCR1A = 0;
  TCCR1A = (1 << COM1A1) | (1 << COM1B1) | (1 << WGM11);
  TCCR1B = 0;
  TCCR1B = (1 << WGM13) | (1 << WGM12) | (1 << CS11);
  ICR1 = 40000;
  OCR1A = 3000;
  OCR1B = 3600;
}

void loop() {
  topleft = analogRead(A0);
  topright = analogRead(A1);
  downleft = analogRead(A2);
  downright = analogRead(A3);

  if (topleft > topright) {
    OCR1A = OCR1A + 1;
    delay(waittime);
  }
  if (downleft > downright) {
    OCR1A = OCR1A + 1;
    delay(waittime);
  }
  if (topleft < topright) {
    OCR1A = OCR1A - 1;
    delay(waittime);
  }
  if (downleft < downright) {
    OCR1A = OCR1A - 1;
    delay(waittime);
  }
  if (OCR1A > 4000) {
    OCR1A = 4000;
  }
  if (OCR1A < 2000) {
    OCR1A = 2000;
  }
  if (topleft > downleft) {
    OCR1B = OCR1B - 1;
    delay(waittime);
  }
  if (topright > downright) {
    OCR1B = OCR1B - 1;
    delay(waittime);
  }
  if (topleft < downleft) {
    OCR1B = OCR1B + 1;
    delay(waittime);
  }
  if (topright < downright) {
    OCR1B = OCR1B + 1;
    delay(waittime);
  }
  if (OCR1B > 4200) {
    OCR1B = 4200;
  }
  if (OCR1B < 3000) {
    OCR1B = 3000;
  }
}