function button_click(colr) {
  Hide('buttons');
  g_n++;
  if (g_cards[1]==g_cards[4]) {
    if (colr=='green') g_score++;
  } else {
    if (colr=='red') g_score++;
  }
  var image=document.getElementById(1);
  image.src='cards/'+g_cards[1]+'.png';
  var image=document.getElementById(4);
  image.src='cards/'+g_cards[4]+'.png';
  // wait two seconds

  for (var i=0;i<5;i++) {
    var image=document.getElementById(i);
    image.src='cards/back.png';
  }
  pick0();
  var image=document.getElementById(0);
  image.src='cards/'+g_cards[0]+'.png';
  // wait three seconds

  var image=document.getElementById(0);
  image.src='cards/back.png';
  move();
  for (var j=4; j>0; j--) g_cards[j]=g_cards[j-1];
  // when move finished

  Show('buttons');
}