robo dog

#include <Servo.h>
#include <NewPing.h>

#define TRIGGER_PIN 6
#define ECHO_PIN 7
#define MAX_DISTANCE 1000
Servo servo1;
Servo servo2;
Servo servo3;
Servo servo4;
NewPing ultrasonic(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE);
const int button1 = 8;
const int button2 = 9;
const int button3 = 10;
int button1state = LOW;
int button2state = LOW;
int button3state = LOW;
int stopcount = 0;
int timecheck = 0;
int speedincrement = 3;

void setup() {
  Serial.begin(9600);
  servo1.attach(2);
  servo2.attach(3);
  servo3.attach(4);
  servo4.attach(5);
  pinMode(button1, INPUT);
  pinMode(button2, INPUT);
}

void loop() {

  int check = ultrasonic.ping();
  int distance = check/US_ROUNDTRIP_CM; //converts distance to cm
  Serial.println(distance);

  button1state = digitalRead(button1); //green
  button2state = digitalRead(button2); //red
  button3state = digitalRead(button3); //yellow

 if(button1state == 1){
  speedincrement += 2;
 }
 else if(button3state == 1){
  speedincrement -= 2;
 }
  
 if(distance <= 25){ //one of the stop commands: there is an obstacle
    while(timecheck <= 10000){
      timecheck++;
    }
    if(timecheck == 10000){ 
      freeze();
    }
  } 
  else if(stopcount >= 1){ //second stop command: second button is held
    freeze();
    stopcount++;
  }
  else if(button2state == 1){ //second stop command ends here
    stopcount = 0;
    speedincrement = 3;
  }
  else{ //base case: walking 
  timecheck = 0;
  walkForward(); 
  }
}

void walkForward(){
  for(int i = 40; i >= 0; i = i - speedincrement){
    delay(10);
    servo1.write(i);
    delay(10);
    servo3.write(120-(i+10));
    delay(10);
  }
   for(int i = 130; i >= 90; i = i - speedincrement){
    delay(10);
    servo2.write(i);
    delay(10);
    servo4.write(190-(i+15));
    delay(10);
  }
}

void freeze(){
  servo1.write(90);
  servo2.write(90);
  servo3.write(90);
  servo4.write(90);
}