#define led1 7
#define led2 6
#define led3 5

bool led1_Status = LOW;
bool led2_Status = LOW;
bool led3_Status = LOW;
unsigned long startTime = 0;

void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
}

void loop() {
  if (led1_Status == LOW) {
    led1_Status = HIGH;
    startTime = millis();  // record the start time
  }

  if (millis() - startTime >= 10000) {  // check if 10 seconds have passed
    led2_Status = HIGH;
  }

  if (millis() - startTime >= 5000) {  // check if 15 seconds have passed (10 + 5)
    led3_Status = HIGH;
  }

  digitalWrite(led1, led1_Status);   // Update LED1 state
  digitalWrite(led2, led2_Status);   // Update LED2 state
  digitalWrite(led3, led3_Status);   // Update LED3 state
}