#include <EEPROM.h>

int leds[16] = {2,3,4,5,6,7,8,9,10,11,12,13,A0,A1,A2,A3};

#define BTN_PIN A4   // Push button

int speedStep = 1;   // 1 = slow, 5 = fast
bool lastBtn = HIGH;

// Fixed delays for speed levels (ms)
int speedDelay[5] = {400, 300, 200, 120, 60};

void setup() {
  for (int i = 0; i < 16; i++) pinMode(leds[i], OUTPUT);
  pinMode(BTN_PIN, INPUT_PULLUP);

  // Load saved speed
  speedStep = EEPROM.read(0);
  if (speedStep < 1 || speedStep > 5) speedStep = 1;
}

void loop() {

  // ---- BUTTON: CHANGE SPEED ----
  bool btn = digitalRead(BTN_PIN);

  if (btn == LOW && lastBtn == HIGH) {
    speedStep++;
    if (speedStep > 5) speedStep = 1;

    EEPROM.write(0, speedStep);  // Save speed
    delay(250);                  // Debounce
  }
  lastBtn = btn;

  // ---- LED RUNNING PATTERN ----
  for (int i = 0; i < 16; i++) {
    allOff();
    digitalWrite(leds[i], HIGH);
    delay(speedDelay[speedStep - 1]);
  }
}

// ---- TURN ALL LEDS OFF ----
void allOff() {
  for (int i = 0; i < 16; i++) digitalWrite(leds[i], LOW);
}