assets/css/less/extend/button.less
// Core
.button {
  .inline-block();
  padding: 4px 15px;
  margin-bottom: 0; // For input.button
  font-size: 14px;
  line-height: @baseLineHeight;
  font-weight:bold;
  color: @grayDark;
  text-align: center;
  text-shadow: 0 1px 1px rgba(255,255,255,.75);
  .buttonBackground(@btnBackground, @btnBackgroundHighlight);
  border: 1px solid @btnBorder;
  border-bottom-color: darken(@btnBorder, 10%);
  .border-radius(@radius);
  @shadow: inset 0 1px 0 rgba(255,255,255,.2), 0 1px 2px rgba(0,0,0,.05);
  .box-shadow(@shadow);
  cursor: pointer;

  // Give IE7 some love
  .ie7-restore-left-whitespace();
}

// Hover state
.button:hover{
  color: @grayDark;
  text-decoration: none;
  background-color: darken(@white, 10%);
  background-position: 0 -15px;

  // transition is only when going to hover, otherwise the background
  // behind the gradient (there for IE<=9 fallback) gets mismatched
  .transition(background-position .1s linear);
}


// Focus state for keyboard and accessibility
.button:focus {
  .tab-focus();
}

// Active state
.button.active,
.button:active {
  background-image: none;
  @shadow: inset 0 2px 4px rgba(0,0,0,.15), 0 1px 2px rgba(0,0,0,.05);
  .box-shadow(@shadow);
  background-color: darken(@white, 10%);
  background-color: darken(@white, 15%) e("\9");
  outline: 0;
}

// Disabled state
.button[disabled] {
  cursor: default;
  outline-width :0;
  background-image: none;
  background-color: darken(@white, 10%);
  .opacity(65);
  .box-shadow(none);
}

// Small
.button-small {
  padding: 2px 10px;
  font-size: 12px;
  font-weight:normal;
  line-height: @baseLineHeight - 2px;
}

// Alternate buttons
// --------------------------------------------------

// Set text color
// -------------------------
.button-primary,
.button-primary:hover {
  text-shadow: 0 -1px 0 rgba(0,0,0,.25);
  color: @white;
}
// Provide *some* extra contrast for those who can get it
.button-primary.active {
  color: rgba(255,255,255,.75);
}

// Set the backgrounds
// -------------------------
.button-primary {
  .buttonBackground(@btnPrimaryBackground, @btnPrimaryBackgroundHighlight);
}