int leds[5] = {13, 12, 11, 10, 9};
int buttons[5] = {8, 7, 6, 5, 4};
int niveau = 0;
int ledList[32];

void setup() {
    for(int i = 0; i<5;i++){
        pinMode(leds[i], OUTPUT);
        pinMode(buttons[i],INPUT); //Initializing button as input
        digitalWrite(buttons[i],HIGH); //Enabling the internal Arduino pullup-resistor
    }
}
void ledSequence()
{
    for(int i=0; i<=niveau; i++)
    {
        digitalWrite(ledList[i + 8],HIGH);
        delay(1000);
        digitalWrite(ledList[i + 8],LOW);
        delay(1000);
    }
}
void loop()
{
    ledList[niveau] = random(1 , 5);
    ledSequence();
    delay(2000);
    niveau++;
}