#define LED_L 10
#define DelayTime 200
#define LIGHT 0
#define DARK 1
const int Led[LED_L] = { 2,3,4,5,6,7,8,9,10,11 };
const int Speed[LED_L * 2] = { 1, 1, 1, 2, 2, 2, 4, 6, 8, 8, 12, 20, 30, 40, 50, 60, 70, 80, 90, 100 };

//int buffer[LED_L];
void setup() {
  for (int i = 0;i<LED_L;i++) {
    pinMode(Led[i], OUTPUT);
    digitalWrite(Led[i], DARK); 
  }
}
#define DB 4 //底線最高
#define DU 2 //最少長度
void loop() {
  int i,c,a,b,d;
  a =  random(DB+2);//0 出現機率為 3,其他為 1
  if(a>=DB) a=0;
  b = random(LED_L - a) + a + DU;
  if(b>=LED_L) b = LED_L - 1;
  for (i = c = 0; i <= a ; i++, c++) 
    digitalWrite(Led[i], LIGHT);
  for ( ; i <= b ; i++, c++) {
    digitalWrite(Led[i], LIGHT);  
    delay(Speed[c]);
  }
  c = (LED_L <<1) - b -2;
  d = random(DB);
  for (i = b; i >=d; i--, c++) {
    digitalWrite(Led[i], DARK);
    delay(Speed[c]);
  }
  if(i<=0) delay(DelayTime);
}