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

// 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) light=0;                  // on state 0 light is OFF
  if (state==1) light=32;                 // on state 1 light is dim
  if (state==2) light=255;                // on state 2 light is ON
 
  analogWrite(LED,light);     
  butt_old=butt;
  delay(50);                               // to avoid button rebounds
  
}