// -------- PIN SETUP --------
#define BUTTON_PIN D8     // button input (INPUT_PULLDOWN)
#define LED_PIN D2        // yellow LED

// -------- TIMING CONFIG --------
const unsigned long debounceDelay = 50;

const unsigned long longPressTime = 1000;

const unsigned long doublePressGap = 400;

// -------- SYSTEM STATE --------
int totalAmount = 0;

int goal = 100;

bool milestone25 = false;
bool milestone50 = false;
bool milestone75 = false;
bool milestone100 = false;

// -------- BUTTON STATE --------
bool buttonState = LOW;
bool lastButtonReading = LOW;

unsigned long lastDebounceTime = 0;
unsigned long pressStartTime = 0;
unsigned long lastReleaseTime = 0;

int pressCount = 0;

// -------- SETUP --------
void setup() {
Serial.begin(115200);

pinMode(BUTTON_PIN, INPUT_PULLDOWN);
pinMode(LED_PIN, OUTPUT);

digitalWrite(LED_PIN, LOW); // LED OFF initially
}

// -------- LOOP --------
void loop() {

int reading = digitalRead(BUTTON_PIN);

// -------- DEBOUNCE --------
if (reading != lastButtonReading) {
lastDebounceTime = millis();
}

if ((millis() - lastDebounceTime) > debounceDelay) {

```
if (reading != buttonState) {
  buttonState = reading;

  // -------- BUTTON PRESSED --------
  if (buttonState == HIGH) {
    pressStartTime = millis();
  }

  // -------- BUTTON RELEASED --------
  else {
    unsigned long pressDuration = millis() - pressStartTime;

    // -------- LONG PRESS --------
    if (pressDuration >= longPressTime) {
      handleLongPress();
      pressCount = 0;
    }
    else {
      pressCount++;
      lastReleaseTime = millis();
    }
  }
}
```

}

// -------- SINGLE / DOUBLE --------
if (pressCount > 0 && (millis() - lastReleaseTime) > doublePressGap) {

```
if (pressCount == 1) {
  handleSinglePress();
}
else if (pressCount == 2) {
  handleDoublePress();
}

pressCount = 0;
```

}

lastButtonReading = reading;
}

// -------- ACTIONS --------

// Single press → ₹1
void handleSinglePress() {
addAmount(1);
blinkLED(1);
}

// Double press → ₹2
void handleDoublePress() {
addAmount(2);
blinkLED(2);
}

// Long press → ₹5
void handleLongPress() {
addAmount(5);

// longer glow
digitalWrite(LED_PIN, HIGH);
delay(400);
digitalWrite(LED_PIN, LOW);
}

// -------- CORE LOGIC --------

void addAmount(int value) {

// prevent adding after goal already reached
if (milestone100) return;

totalAmount += value;

// clamp to goal
if (totalAmount > goal) {
totalAmount = goal;
}

int percentage = (totalAmount * 100) / goal;

Serial.print("Added: ");
Serial.print(value);
Serial.print(" | Total: ");
Serial.print(totalAmount);
Serial.print(" | ");
Serial.print(percentage);
Serial.println("%");

checkMilestones(percentage);
}

// -------- LED HELPER --------

void blinkLED(int times) {
for (int i = 0; i < times; i++) {
digitalWrite(LED_PIN, HIGH);
delay(120);
digitalWrite(LED_PIN, LOW);
delay(120);
}
}

// -------- RESET SYSTEM --------

void resetSystem() {

totalAmount = 0;

milestone25 = false;
milestone50 = false;
milestone75 = false;
milestone100 = false;

Serial.println("System Reset → Back to 0%");
}

// -------- MILESTONE LOGIC --------

void checkMilestones(int percentage) {

if (!milestone25 && percentage >= 25) {
milestone25 = true;
Serial.println("Milestone: 25% reached");
}

if (!milestone50 && percentage >= 50) {
milestone50 = true;
Serial.println("Milestone: 50% reached");
}

if (!milestone75 && percentage >= 75) {
milestone75 = true;
Serial.println("Milestone: 75% reached");
}

if (!milestone100 && percentage >= 100) {
milestone100 = true;

```
Serial.println("Milestone: Goal reached!");

// -------- CELEBRATION --------
for (int i = 0; i < 3; i++) {
  digitalWrite(LED_PIN, HIGH);
  delay(150);
  digitalWrite(LED_PIN, LOW);
  delay(150);
}

delay(500); // pause before reset

resetSystem(); // restart cycle
```

}
}