Arduino wire cutter code

//------------------------------- librarys ----------------------------------
#include <Wire.h>
#include <rgb_lcd.h>
#include <Servo.h>

//------------------------------- lcd ----------------------------------
rgb_lcd lcd;

//------------------------------- stepper ----------------------------------
#define stepPin 7
#define dirPin 8

//------------------------------- servo ----------------------------------
Servo snippers;
#define servo 10
#define openAngle 90
#define closedAngle 0

//------------------------------- input ----------------------------------

#define leftButton 3
#define rightButton 2
#define upButton 4
#define downButton 5

//------------------------------- user settings ----------------------------------
unsigned int wireLength = 0;
unsigned int wireQuantity = 0;

//------------------------------- system settings ----------------------------------
int state = 0;
int incrementSpeed = 1;
int previousWireLength = 0;
int previousWireQuantity = 0;
float mmPerStep = 0.18096;


void setup() {
  Serial.begin(9600);


  lcd.begin(16, 2); //LCD columns and rows
  lcd.setRGB(255,255,0); //backlight colour

  pinMode(upButton, INPUT_PULLUP);
  pinMode(downButton, INPUT_PULLUP);
  pinMode(leftButton, INPUT_PULLUP);
  pinMode(rightButton, INPUT_PULLUP);

  pinMode(stepPin,OUTPUT);
  pinMode(dirPin,OUTPUT);

  snippers.attach(servo);

  snippers.write(openAngle);

  delay(1000);
}

void loop() {
  if (!digitalRead(rightButton)){
    if(state == 5){
      state = 0;
    }
    else{
      state += 1;
    }
    delay(200);
    lcd.clear();
  }
  if (!digitalRead(leftButton) && state > 0 && state < 4){
    state -=1;
    delay(200);
    lcd.clear();
  }


  switch (state){
    case 0:
      homeScreen();
      break;
    case 1:
       chooseWireLength();
       break;
    case 2:
      chooseWireQuantity();
      break;
    case 3:
      confirm();
      break;
    case 4:
      currentlyCutting();
      break;
    case 5:
      finishedCutting();
      break;
  }

}


void homeScreen(){
  lcd.setCursor(0, 0);
  lcd.print("WIRE CUTTER");
  lcd.setCursor(11, 1);
  lcd.print("NEXT>");
  delay(100);
}


void chooseWireLength(){
  wireLength = changeValue(wireLength);

  //clear LCD if required
  if(previousWireLength != wireLength){
    lcd.clear();
    previousWireLength = wireLength;
  }

  //Display information on LCD
  lcd.setCursor(0, 0);
  lcd.print("LENGTH:" + (String)wireLength + "mm");
  displayNavigation();
}

void chooseWireQuantity(){
  wireQuantity = changeValue(wireQuantity);

  //clear LCD if required
  if(previousWireQuantity != wireQuantity){
    lcd.clear();
    previousWireQuantity = wireQuantity;
  }

  //Display information on LCD
  lcd.setCursor(0, 0);
  lcd.print("QUANTITY:" + (String)wireQuantity);
  displayNavigation();
}

void confirm(){
  lcd.setCursor(0, 0);
  lcd.print((String)wireLength + "mm x " + (String)wireQuantity + "pcs");
  lcd.setCursor(0, 1);
  lcd.print("<BACK");
  lcd.setCursor(10, 1);
  lcd.print("START>");
  delay(100);
}

void currentlyCutting(){
  lcd.setCursor(0, 0);
  lcd.print((String)0 + "/" + (String)wireQuantity);
  lcd.setCursor(0, 1);
  lcd.print("???s");
  int stepsToTake = (int)wireLength/mmPerStep;
  for(int i = 0; i < wireQuantity; i++){
    unsigned long timeForOneCycle = millis();
    digitalWrite(dirPin,HIGH);
    for(int x = 0; x < stepsToTake; x++) {
      digitalWrite(stepPin,HIGH);
      delayMicroseconds(500);
      digitalWrite(stepPin,LOW);
      delayMicroseconds(500);
    }

    lcd.setCursor(0, 0);
    lcd.print((String)(i+1) + "/" + (String)wireQuantity);

    snippers.write(closedAngle);
    delay(600);
    snippers.write(openAngle);
    delay(600);


    lcd.setCursor(0, 1);

    unsigned long timeRemaining = ((millis() - timeForOneCycle)*(wireQuantity - (i+1)))/1000;
    lcd.print((String)timeRemaining + "s    ");

  }
  wireLength = 0;
  wireQuantity = 0;
  state = 5;
}

void finishedCutting(){
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("CUTTING COMPLETE");
  lcd.setCursor(11, 1);
  lcd.print("NEXT>");
  delay(100);
}


int changeValue(int currentValue){
  if (!digitalRead(upButton)) {
    currentValue += incrementSpeed;
    incrementSpeed ++;
  }
  if (!digitalRead(downButton)) {
    if(currentValue - incrementSpeed >= 0){
      currentValue -= incrementSpeed;
      incrementSpeed ++;
    }
    else{
      currentValue = 0;
    }
  }
  if (digitalRead(downButton) && digitalRead(upButton)){
    incrementSpeed = 1;
  }
  return currentValue;
}

void displayNavigation(){
  lcd.setCursor(0, 1);
  lcd.print("<BACK");
  lcd.setCursor(11, 1);
  lcd.print("NEXT>");
  delay(100);
}