String filenames[] = {"nuclear1.png", "nuclear2.png", "nuclear3.png", "nuclear4.png", "nuclear5.png"};

PImage images[] = new PImage[filenames.length];
void setup() {
  for (int i = 0; i < filenames.length; i++) {
    images[i] = loadImage(filenames[i]);
  }
  size(800, 800);
  nextchange = second();
}

int picture = 0;
int nextchange;
void draw() {
  image(images[picture], 0, 0);
  if (second() == nextchange) {
    nextchange = second() + 2; // 2 is the delay
    if (nextchange >= 60)
      nextchange -= 60;
    picture++;
    if (picture >= filenames.length)
      picture = 0;
  }
}

void mouseClicked() {
  picture++;
  if (picture >= filenames.length)
    picture = 0;
}

void keyPressed() {
   //if(key == '4')
   //  println("You pressed 4");
   // (key - '0') is the number value of the digit that was pressed IF 
   // the user pushed a digit.  It's not if the user pushed a letter.
   if(key == '0'){
      nextchange = 61; 
   } else {
      nextchange = second() + 1; 
   }
}