int estado=0;
int B1 = 2;
int B2 = 3;
int B3 = 4;

void setup() {
  pinMode(13,OUTPUT);
  pinMode(B1, INPUT);
  pinMode(B2, INPUT);
  pinMode(B3, INPUT);
}

void estado0(){
  digitalWrite(13, LOW);
  if(digitalRead(B1)){
    estado = 1;
    while(digitalRead(B1)) delay(15);
  }

  if(digitalRead(B2)){
    estado = 3;
    while(digitalRead(B2)) delay(15);
  }
}

void estado1(){
  digitalWrite(13, HIGH);
  delay(100);
  digitalWrite(13,LOW);
  delay(100);
  if(digitalRead(B1)){
    estado = 2;
    while(digitalRead(B1)) delay(15);
  }

  if(digitalRead(B2)){
    estado = 0;
    while(digitalRead(B2)) delay(15);
  }

  if(digitalRead(B3)){
    estado = 3;
    while(digitalRead(B3)) delay(15);
  }
}

void estado2(){
  digitalWrite(13, HIGH);
  if(digitalRead(B2)){
    estado = 1;
    while(digitalRead(B2)) delay(15);
  }

  if(digitalRead(B1)){
    estado = 3;
    while(digitalRead(B1)) delay(15);
  }
}

void estado3(){
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13,LOW);
  delay(1000);
  if(digitalRead(B1)){
    estado = 0;
    while(digitalRead(B1)) delay(15);
  }

  if(digitalRead(B2)){
    estado = 2;
    while(digitalRead(B2)) delay(15);
  }

  if(digitalRead(B3)){
    estado = 1;
    while(digitalRead(B3)) delay(15);
  }
}

void loop() {
  switch(estado){
    case 0:
      estado0();
      break;
    case 1:
      estado1();
      break;
    case 2:
      estado2();
      break;
    case 3:
      estado3();
      break;
  }
}