function setImage(index) {
  // clear all
  for (i=0; i<8; i++) {
    document.getElementById('dot'+i).setAttribute('class', 'none');
  }
  // set it to current
  document.getElementById('dot'+index).setAttribute('class', 'current');
  // hide all
  for (i=0; i<8; i++) {
    hideElement('iphone_screenshot'+(i+1));
  }
  // show current
  showElement('iphone_screenshot'+(index+1));
}

function getCurrent() {
  for (i=0; i<8; i++) {
    if (document.getElementById('dot'+i).getAttribute('class') == 'current') {
      return i;
    }
  }
  return 0;
}

function setImage2(index) {
  // clear all
  for (i=0; i<6; i++) {
    document.getElementById('dot2'+i).setAttribute('class', 'none');
  }
  // set it to current
  document.getElementById('dot2'+index).setAttribute('class', 'current');
  // hide all
  for (i=0; i<6; i++) {
    hideElement('ipad_screenshot'+(i+1));
  }
  // show current
  showElement('ipad_screenshot'+(index+1));
}

function getCurrent2() {
  for (i=0; i<6; i++) {
    if (document.getElementById('dot2'+i).getAttribute('class') == 'current') {
      return i;
    }
  }
  return 0;
}

function selectiPhoneButton() {
  img = new Image();
  img.src = 'iphone_sel.png';
  document['iphone_btn'].src = img.src;
  img2 = new Image();
  img2.src = 'ipad_btn.png';
  document['ipad_btn'].src = img2.src;
  showElement('iphone_screenshot');
  showElement('iphone_screenshot'+(getCurrent()+1));
  hideElement('ipad_screenshot');
  hideElement('ipad_screenshot'+(getCurrent2()+1));
}

function selectiPadButton() {
  img = new Image();
  img.src = 'iphone_btn.png';
  document['iphone_btn'].src = img.src;
  img2 = new Image();
  img2.src = 'ipad_sel.png';
  document['ipad_btn'].src = img2.src;
  hideElement('iphone_screenshot');
  hideElement('iphone_screenshot'+(getCurrent()+1));
  showElement('ipad_screenshot');
  showElement('ipad_screenshot'+(getCurrent2()+1));
}

function showElement(elem) {
  document.getElementById(elem).style.visibility = 'visible';
}

function hideElement(elem) {
  document.getElementById(elem).style.visibility = 'hidden';
}