const int buttonpin1=3;
const int buttonpin2=11;
const int ledpin=6;
unsigned int buttonval1;
unsigned int buttonval2;
unsigned int oldbuttonval1 = 1;
unsigned int oldbuttonval2=1;
unsigned int ledstate=0;
unsigned int low=63;
unsigned int med=127;
unsigned int led_percent;
void setup() {
  // put your setup code here, to run once:
pinMode(buttonpin1, INPUT_PULLUP);
pinMode(buttonpin2, INPUT_PULLUP);
pinMode(ledpin, OUTPUT);
Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
buttonval1=digitalRead(buttonpin1);//value of green button
buttonval2=digitalRead(buttonpin2);//value of black button
// execution on the input of green button 
// led brightness is increasing with each toogle of green button
if(oldbuttonval1==HIGH && buttonval1==LOW){ 
  delay(200); //debouncing time
  switch(ledstate){
    case 0:analogWrite(ledpin,low);
           Serial.println("the percentage of led brightness: ");
           Serial.println("25");
           ledstate=1;
           break;
    case 1:analogWrite(ledpin,med);
           Serial.println("the percentage of led brightness: " );
           Serial.println("50");
           ledstate=2;
           break;   
    case 2:analogWrite(ledpin,HIGH);
           Serial.println("the percentage of led brightness:");
           Serial.println("100");
           ledstate=3;
           break;
           
    default:analogWrite(ledpin,HIGH); 
            Serial.println("the percentage of led brightness:");
            Serial.println("100");
            ledstate=3;
            break;  
  }   

}
// execution on the input of black button 
// led brightness is decreasing with each toogle of black button
  if(oldbuttonval2==HIGH && buttonval2==LOW){
  delay(200);
  switch(ledstate){
    case 3:analogWrite(ledpin,med);
           Serial.println("the percentage of led brightness: ");
           Serial.println("50");
           ledstate=2;
           break;
    case 2:analogWrite(ledpin,low);
           Serial.println("the percentage of led brightness: " );
           Serial.println("25");
           ledstate=1;
           break;   
    case 1:analogWrite(ledpin,LOW);
           Serial.println("the percentage of led brightness:");
           Serial.println("0");

          ledstate=0;
           break;
    default:analogWrite(ledpin,LOW); 
            Serial.println("the percentage of led brightness:");
            Serial.println("0");
            ledstate=0;                  
            break;                
  }
 
  }
   oldbuttonval1=buttonval1;  
   
   oldbuttonval2=buttonval2;  
}