#define latchPin 1
#define clockPin 2
#define dataPin 0
#define buttonPin 4

const byte pattern[7] = {
  0b00000001,  // 0 blank
  0b00010000,  // 1
  0b00100010,  // 2
  0b00110010,  // 3
  0b10101010,  // 4
  0b10111010,  // 5
  0b11101110   // 6
};
void setup() {
  pinMode(latchPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP);
  randomSeed(analogRead(A3));  // Initializing the random generator
}

void displayDigit(byte d) {
  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, MSBFIRST, pattern[d]);
  digitalWrite(latchPin, HIGH);
}

void loop() {
  if (digitalRead(buttonPin) == LOW) {
    delay(20);
    displayDigit(random(1, 7));
    while(digitalRead(buttonPin) == LOW);
    delay(1500);
  } else {
    displayDigit(0);
  }
  //   for (byte d=0; d<7; d++) {
  //   displayDigit(d);
  //   delay(500);
  // }
}