.menu {
  z-index: 4;
  width: 100%;
  min-height: 2em;
  background-color:green;
  position: absolute;
  transition-property: opacity;
  transition-duration: 1s;
  text-align: center;
  color: white;
}

.menu:hover {
  /* Unhide the menu when the mouse hovers on it*/
  opacity: 1;
}

.menu.hidden_text {
  color: green;
}


/**
 * Positionning classes.
 */

.left {
  left: 0;
  text-align: left;
}

.right {
  right: 0;
  text-align: right;
}

.pull_left {
  float: left;
}

.pull_right {
  float: right;
}

.clearfloats {
  clear: both;
}

.top {
  position: absolute;
  top: 0;
  width: 100%;

  border-bottom-left-radius: 10px 7px;
  border-bottom-right-radius: 10px 7px;
}

.bottom {
  position: absolute;
  bottom: 0;
}

.menu_height {
  padding: .5em;
  width: 1em;
  height: 1em;
  cursor: pointer;
}

.padding_wrapper {
  padding: 10px 10px;
}

#menu_top_contents {
  font-weight: bold;
}

/**
 * Menu buttons
 */

.menu_button {
  /* Minimal size for a 1.33em icon. */
  min-height:2em;
  min-width: 2em;

  background: linear-gradient(to bottom, rgb(32, 164, 32), darkgreen);
  border: : 2px solid darkgreen;
  box-shadow: 0px 1px 2px rgb(34, 34, 34);
  border-radius: 5px 5px;
}

.menu_button:hover {
  background: linear-gradient(to bottom, darkgreen, rgb(32, 164, 32));
}

.menu_button:active {
  box-shadow: 0px 1px 2px rgba(34, 34, 34, 0.4) inset;
}

.menu_button > i {
  line-height: 40%;
  vertical-align: bottom;
}

/**
 * Drop down menu
 */

.drop_down_menu ul {
  background-color: green;
  border: 2px solid darkgreen;
  border-radius: 3px 3px;

  position: absolute;
  top: 40px; /* below minimal menu height bar + 5 pixels margin */
  right: 10px; /* same as menu padding */

  min-width: 20vw;
  max-width: 60vw;
  padding: 10px 0px;

  list-style: none;

  transition-property: height, opacity;
  transition-duration: 1s;
  overflow-y: hidden;

  font-family: sans-serif;
  font-size: 1.05em;
}

@media (max-width: 1000px) {
  .drop_down_menu ul {
    min-width: 30vw;
  }
}

@media (max-width: 700px) {
  .drop_down_menu ul {
    min-width: 60vw;
  }
}

.drop_down_menu li {
  min-height: 1.5em;
  display: block;
  text-align: right;
  padding: 1px 10px;
}

.drop_down_menu li:hover {
  background-color: darkgreen;
}

.menu_option_title {
  display: inline-block;
  float: left;
}

.drop_down_menu input {
  width: 2em;
  background-color: green;
  border: none;
  color: white;
  padding: 0;
  margin: 0;
  text-align: right;
}

.folded_up {
  height: 0;
  opacity: 0;
}

.unfolded_up {
  height: 3em;
  opacity: 1;
}

.right > .drop_down_menu ul {
  right: 0;
}

.top > .drop_down_menu ul {
  top: 1em;
}

.fade_inout {
  transition-property: opacity;
  transition-duration: 1s;
}

/**
 * Buttons
 */
span.button {
  box-shadow: 2px 2px darkgreen;
  transform: translate(-1px, -1px);
  width: 1.5em;
  height: 1.5em;
  padding: 0;
  margin: 0;
  text-align: center;
  vertical-align: middle;
  display: inline-block;
  background-color: rgb(0, 140, 0);
}

span.button.lowered {
  box-shadow: none;
  transform: translate(0, 0);
}

.passive_theme {
  opacity: .3;
}

.active_theme {

}