void setup() {
  for (int pin = 2; pin <= 19; pin++) {
    pinMode(pin, OUTPUT);
  }

}

void loop() {
  loop1();
  //onrun(random(20, 50));
  //alternate(random(80, 100));
  //onrun(random(20, 50));
  //offrun(random(20, 50));
  // flash(random(random(20, 50), 300));
  //fadeflash(random(random(20, 50), 300));
  //stack(random(30, 50));
  // chaser(random(80, 100));
}

void loop1() {
  int pickme = random(1, 20); // picks a random pattern of LED patterns
  switch (pickme) {
    case 1:
      onrun(random(20, 50));
      break;
    case 2:
      alternate(random(80, 100));
      break;
    case 3:
      offrun(random(20, 50));
      break;
    case 4:
      stack(random(30, 50));
      break;
    case 5:
      chaser(random(80, 100));
      break;
    case 6:
      fadealter(random(80, 100));
      break;
  }
}

void clearall() {
  for (int pin = 2; pin <= 19; pin++) {
    digitalWrite(pin, LOW);
  }
}

void fillall() {
  for (int pin = 2; pin <= 19; pin++) {
    digitalWrite(pin, HIGH);
  }
}

//One ON LED Run and all other OFF
void onrun(int delaytime) {
  for (int pin = 2; pin <= 19; pin++) {
    clearall();
    digitalWrite(pin, HIGH);
    delay(delaytime);
  }
  for (int pin = 18; pin >= 2; pin--) {
    clearall();
    digitalWrite(pin, HIGH);
    delay(delaytime);
  }
}

//One OFF LED Run and all other OFF
void offrun(int delaytime) {
  for (int pin = 2; pin <= 19; pin++) {
    fillall();
    digitalWrite(pin, LOW);
    delay(delaytime);
  }
  for (int pin = 18; pin >= 2; pin--) {
    fillall();
    digitalWrite(pin, LOW);
    delay(delaytime);
  }
}

//Flashing all LEDs ON and OFF
void flash(int delaytime) {
  for (int i = 1; i <= 20; i++) {
    clearall();
    delay(delaytime);
    fillall();
    delay(delaytime);
  }
}

//Flashing LeD in Fade manner
void fadeflash(int delaytime) {
  clearall();
  int newdelay = delaytime / 5;
  for (int fade = 0; fade <= 255; fade += 5) {
    for (int pin = 2; pin <= 19; pin++) {
      analogWrite(pin, fade);
    }
    delay(newdelay);
  }
  for (int fade = 255; fade >= 0; fade -= 5) {
    for (int pin = 2; pin <= 19; pin++) {
      analogWrite(pin, fade);
    }
    delay(newdelay);
  }
}

//Alternatively Fade & Brightens
void fadealter(int delaytime) {
  clearall();
  int newdelay = delaytime / 5;
  for (int fade = 0; fade <= 255; fade += 5) {
    for (int i = 2; i <= 18; i += 2) {
      analogWrite(i, fade);
    }
    for (int j = 3; j <= 19; j += 2) {
      analogWrite(j, 255 - fade);
    }
    delay(newdelay);
  }
  for (int fade = 255; fade >= 0; fade -= 5) {
    for (int i = 2; i <= 18; i += 2) {
      analogWrite(i, fade);
    }
    for (int j = 3; j <= 19; j += 2) {
      analogWrite(j, 255 - fade);
    }
    delay(newdelay);
  }
}

//Alternate Flash - Similar to Flash but alternate LEDs
void alternate(int delaytime) {
  for (int n = 1; n <= 5; n++) {
    clearall();
    for (int i = 2; i <= 18; i += 2) {
      digitalWrite(i, HIGH);
    }
    delay(delaytime);
    clearall();
    for (int j = 3; j <= 19; j += 2) {
      digitalWrite(j, HIGH);
    } delay(delaytime);
  }
}

//Putting all LEDs one by one in a stack
void stack(int delaytime) {
  int stack = 0;
  while (stack < 18) {
    for (int pos = 2; pos <= (19 - stack); pos++) {
      clearall();
      digitalWrite(pos, HIGH);
      drawstack(stack);
      delay(delaytime);
    } stack++;
  }
}

//Subfunction of the stack function
void drawstack(int stack) {
  for (int n = 19; n < (19 - stack); n--) {
    if (n >= 2) {
      digitalWrite(n, HIGH);
    }
  }
}

//One LED chases another LED front and back
void chaser(int delaytime) {
  int div = 40;
  int flashtime = delaytime / div;
  int A = random(2, 7);
  int B = random(7, 12);
  int Av = 1;
  int Bv = 1;

  if (random(0, 2)) {
    Av *= -1;
  }
  if (random(0, 2)) {
    Bv *= -1;
  }

  for (int time = 1; time < 100; time++) {
    if (abs(A - B) == 1 && (Av * Bv) == -1) {
      for (int f = 1; f < round(div / 4); f++) {
        clearall();
        delay(flashtime);
        digitalWrite(A, HIGH);
        digitalWrite(B, HIGH);
        delay(flashtime);
      }
      Av *= -1;
      Bv *= -1;
      A += Av;
      B += Bv;
    }
    else {
      clearall();
      digitalWrite(A, HIGH);
      digitalWrite(B, HIGH);
      A += Av;
      B += Bv;
      delay(delaytime);
    }
    if (A < 2) {
      A = 3;
      Av *= -1;
    }
    if (B > 19) {
      B = 18;
      Bv *= -1;
    }
    if (A >= B) {
      A = B - 1;
    }
  }
}