// variable definition
const int LED = 9;
const int BUTTON = 7;
int butt,butt_old,state,light1,light2;

// Arduino init
void setup() {
pinMode(LED, OUTPUT);
pinMode(BUTTON, INPUT);
state=0;
}

// Arduino loop
void loop() {
  butt=digitalRead(BUTTON);
  if ((butt-butt_old)==1) state=state+1;  // state changes during the rising edge of "butt"
  if (state==3) state=0;                  // state cycle among 0, 1 or 2
  
  if (state==0) {light1=0;light2=0;}      // on state 0 both lights ar turned OFF
  if (state==1) {light1=1;light2=0;}      // on state 1 one light is ON and one is OFF
  if (state==2) {light1=1;light2=1;}      // on state 2 both lights ar turned ON
 
 // cycle between the two lights states
  digitalWrite(LED, light1);       
  delay(10);               
  digitalWrite(LED, light2);    
  delay(100);              
  
  butt_old=butt;                          // update butt_old variable
  
}