Bluetooth controlled robot with Arduino code

To make a Bluetooth controlled robot, watch step by step full video on my youtube channel: https://youtu.be/PNm-9I9KAR8

Arduino code:

#define m11 11 // M1a
 #define m12 12 // M1b
 #define m21 10 // M2a
 #define m22 9 // M2b
 void forward()
 {
 digitalWrite(m11, HIGH);
 digitalWrite(m12, LOW);
 digitalWrite(m21, HIGH);
 digitalWrite(m22, LOW);
 }
 void left()
 {
 digitalWrite(m11, LOW);
 digitalWrite(m12, HIGH);
 digitalWrite(m21, HIGH);
 digitalWrite(m22, LOW);
 }
 void backward()
 {
 digitalWrite(m11, LOW);
 digitalWrite(m12, HIGH);
 digitalWrite(m21, LOW);
 digitalWrite(m22, HIGH);
 }
 void right()
 {
 digitalWrite(m11, HIGH);
 digitalWrite(m12, LOW);
 digitalWrite(m21, LOW);
 digitalWrite(m22, HIGH);
 }
 void Stop()
 {
 digitalWrite(m11, LOW);
 digitalWrite(m12, LOW);
 digitalWrite(m21, LOW);
 digitalWrite(m22, LOW);
 }
 void setup()
 {
 Serial.begin(9600);
 pinMode(m11, OUTPUT);
 pinMode(m12, OUTPUT);
 pinMode(m21, OUTPUT);
 pinMode(m22, OUTPUT);
 }
 void loop()
 {
 while(Serial.available())
 {
 char data = Serial.read();
 if(data =='1') // forward
 {
 Serial.println("Forward");
 forward();
}
 else if(data =='2') //left
 {
 Serial.println("Left");
 right();
}
 else if(data =='3') //right
 {
 Serial.println("right");
 left();
}
else if(data =='4') //backward
 {
 Serial.println("backward");
 backward();
}
 else if(data =='5') //stop
 {
 Serial.println("stop");
 Stop();
}
}
 }