#include <LiquidCrystal.h>              //lets you use the LCD


LiquidCrystal lcd(8, 9, 4, 5, 6, 7);     // The different pins the shield relies on.

const int a0 = a0;            //the pin that detects buttons
int val = 0;                  // when you’re finished inputting your first number
int number = 0;              //your first number
int number1 = 0;              // your second number
int val2 = 0;                //When you have input your second number
int total = 0;              //The Answer to your math
int op = 1023;              //Reading A0 to determine what function on the calculator you are using
char opc = 'NONE';          // This is what your function will be stored as

byte divide[8] = {          // this is the division symbol
  B00000,
  B00100,
  B00000,
  B11111,
  B00000,
  B00100,
  B00000,
};


void setup() {

    lcd.begin(16, 2);                      //sets up the lcd for use
    
    lcd.print("Calculator V3");            // this is my third update of the calculator
    delay(1000);  
        lcd.createChar(0, divide);          //this makes up the division symbol for whenever we use lcd.write(byte(0));
    lcd.clear();                            //clears the screen
    
}

void loop() {
  
  while(op > 1000){                      //the button labeled select has an output of 1023 and thats the highest one. So unless you press anything, this will show. These are your options. 
                                         //The LCD has a really interesting way of knowing which button you’re pressing with only using one pin. Tell me if you want me to explain it.
   

  lcd.print("x ");                      // multiplication
  lcd.setCursor(4, 0);                   //sets where the next print will be
    lcd.print("- ");                      //subtraction
  lcd.setCursor(0, 1);
   lcd.print("  + ");                    //addition
   lcd.setCursor(2, 0);
   lcd.write(byte(0));                    //this writes our division symbol



  
  delay(10);
  op = analogRead(a0);                    //reads analog pin 0, which is what the buttons are all connected to
  
 lcd.clear();
  }
  
  if (op == 722){                        // if it reads 722 (select), it prints the following message
  while(4){                                // this is an infinite loop, as 4 has no "true" or "false"
    lcd.clear();                          //
    lcd.print("L = x, U = ");            //
      lcd.write(byte(0));                  //
    lcd.setCursor(0, 1);                //  
    lcd.print("D = +, R = -");            //
    delay(100);                          //waits 1/10 of a second goes back to while in a loop
  }}  
    
  if (op == 309){                        // if you press down, youre formula will be addition
    opc = '+';
  }
  
  if (op == 0){                          //if you press right, your formula will be subtraction
    opc = '-';  
  }
  
  if (op == 480){                      //if you press left, your formula will be multiplication
    opc = 'x';
  }
  
  if (op == 132){                      //if you press up, your formula will be division
    opc = byte(0);
  }
  
  
  lcd.print(number);                 // this prints "Number", which, as of yet, is 0
  delay(10);                         // wait a hundredth of a second
  val = analogRead(a0);              // read analog pin 0
  lcd.clear();                        //clear number from the screen
  lcd.print(number);                  //print the new number, which is still 0 as nothing has been inputted
  


if (val == 132){                    // if you press up, number goes up by one
  number = number + 1;
}

if (val == 0){                      //if you press right, number goes up by 10
  number = number + 10;
}

if (val == 309){                      // if you press down, number goes down by 1
   number = number - 1;
}

if (val == 480){                      //if you press left, number goes down 10
  number = number - 10;
}


delay(100);                            //waits one tenth of a second

if (val == 722){                      // if you press select, the program continues, otherwise, it will go back to where you can change your number again. this all happens in under half a second.
  while(1){
    lcd.clear();                      //clears the screen
    lcd.print(number);                  //prints the number
    lcd.print(" ");                    //space
  lcd.print(opc);                      //prints the operation you chose
      lcd.print(" ");                  // prints a space again
      
  lcd.print(number1);                   //this is like when you chose your first number, only this is for the second number in your operation
  delay(100);
  val2 = analogRead(a0);
  lcd.clear();
  lcd.print(number);
      lcd.print(" ");
  lcd.print(opc);
      lcd.print(" ");
  lcd.print(number1);                    
  
  if (val2 == 132){                  
    number1 = number1 + 1;
  }
  
  if (val2 == 0){
    number1 = number1 + 10;
  }
      
      if (val2 == 480){
        number1 = number1 - 10;
      }  
  if (val2 == 309){
    number1 = number1 - 1;                  //These change your second number, by 1's and 10's, but the second number, not the first
  }
  
  if (val2 == 722){
    lcd.clear();
    

    if (op == 309){
    total = number + number1;
      }
      
      if (op == 0){
    total = number - number1;
      }
      
      if (op == 480){
    total = number * number1;
      }
      
      if (op == 132){
    total = number / number1;
      }
                                              //these combine your numbers via the operation you chose
    
    while(2){                                  //infinite loop displaying your answer
      
     
     
    lcd.print(number);            
        lcd.print(" ");
    lcd.print(opc);
        lcd.print(" ");
    lcd.print(number1);                    //prints your formula on the top line
    lcd.setCursor(0, 1);
    lcd.print(total);                      //prints the total on the second line
    
    if (op == 132){
      lcd.print(" R:");                    //if its division, these lines print the remainder
      lcd.print(number % number1);
    }

    delay(100);
    lcd.clear();
    

    }}
  
  }}
lcd.clear();


  }
  
  
//Press reset to make another calculation