#define LED 7
#define BUTTON A0
#define BLINK 8
#define DELAY 100

void setup() {
  pinMode(LED, OUTPUT);
  pinMode(BUTTON, INPUT);
  pinMode(BLINK, OUTPUT);
}

bool mode() {
  static bool last = HIGH;
  static bool m = HIGH;
  if (last && !digitalRead(BUTTON)) {
    m = !m;
  }
  last = digitalRead(BUTTON);
  return m;
}

void loop() {
  static unsigned long clk = 0;
  static bool blinkValue = HIGH;
  digitalWrite(LED, mode());
  if (millis() - clk > DELAY) {
     blinkValue = !blinkValue;
     clk = millis();
  }
  digitalWrite(BLINK, blinkValue);
  delay(1);
}