Obstacle avoiding robot with Arduino code

To make an obstacle avoiding robot, watch the step by step video on my youtube channel: https://youtu.be/GJ6XHrs9Lf0

Arduino code:

const int trigPin1 = 11;
 const int echoPin1 = 10;
 const int m11 =9; // M1a
 const int m12 =8; // M1b
 const int m21 =7; // M2a
 const int m22 =6; // M2b
const int M11 =5; // M1a
 const int M12 =4; // M1b
 const int M21 =3; // M2a
 const int M22 =2; // M2b
void setup()
 {
 Serial.begin(9600);
 pinMode(trigPin1, OUTPUT);
 pinMode(echoPin1, INPUT);
 pinMode(m11, OUTPUT);
 pinMode(m12, OUTPUT);
 pinMode(m21, OUTPUT);
 pinMode(m22, OUTPUT);
 pinMode(M11, OUTPUT);
 pinMode(M12, OUTPUT);
 pinMode(M21, OUTPUT);
 pinMode(M22, OUTPUT);
 }
 long duration, distance;
void loop()
 {
digitalWrite(trigPin1, LOW);
 delayMicroseconds(5);
 digitalWrite(trigPin1, HIGH);
 delayMicroseconds(5);
 digitalWrite(trigPin1, LOW);
 duration = pulseIn(echoPin1, HIGH);
distance = (duration/2) / 29.1;
if(distance<10) //MOVE LEFT
 {
 digitalWrite(m11, LOW);
 digitalWrite(m12, HIGH);
 digitalWrite(m21, HIGH);
 digitalWrite(m22, LOW);
digitalWrite(M11, LOW);
 digitalWrite(M12, HIGH);
 digitalWrite(M21, HIGH);
 digitalWrite(M22, LOW);
 }
 else //MOVE STRAIGHT
 {
 digitalWrite(m11, HIGH);
 digitalWrite(m12, LOW);
 digitalWrite(m21, HIGH);
 digitalWrite(m22, LOW);
digitalWrite(M11, HIGH);
 digitalWrite(M12, LOW);
 digitalWrite(M21, HIGH);
 digitalWrite(M22, LOW);
 }
 }