Water height

#include <TM1637Display.h>

const int trigPin = 2;       
const int echoPin = 3;       
const int clkPin = 4;         
const int dioPin = 5;        
const int greenLedPin = 6;    
const int redLedPin = 7;     
const int buzzerPin = 8;      

TM1637Display display(clkPin, dioPin); 

void setup() {
  Serial.begin(9600);          
  pinMode(trigPin, OUTPUT);    
  pinMode(echoPin, INPUT);     
  pinMode(greenLedPin, OUTPUT); 
  pinMode(redLedPin, OUTPUT);  
  pinMode(buzzerPin, OUTPUT);   

  display.setBrightness(0x0f);  
}

void loop() {
  long duration, distance;


  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  
  duration = pulseIn(echoPin, HIGH);

  
  distance = (duration * 0.034) / 2; 

 
  display.showNumberDec(distance, false); 


  if (distance < 20) {
    digitalWrite(greenLedPin, LOW);  
    digitalWrite(redLedPin, HIGH);    
    digitalWrite(buzzerPin, HIGH);    
  } else {
    digitalWrite(greenLedPin, HIGH);  
    digitalWrite(redLedPin, LOW);      
    digitalWrite(buzzerPin, LOW);      
  }

  delay(500); 
}