discourse/app/assets/stylesheets/common/components/buttons.scss

// --------------------------------------------------
// Buttons
// --------------------------------------------------

// Base
// --------------------------------------------------

.btn {
  display: inline-block;
  margin: 0;
  padding: 6px 12px;
  font-weight: 500;
  font-size: $font-0;
  line-height: $line-height-medium;
  text-align: center;
  cursor: pointer;
  transition: all .25s;

  &:active, &.btn-active {
    text-shadow: none;
  }
  &[disabled], &.disabled {
    cursor: default;
    opacity: 0.4;
  }
  .fa {
    margin-right: 7px;
  }
  &.no-text {
    .fa {
      margin-right: 0;
    }
  }
}

.btn.hidden {
  display: none;
}

// Default button
// --------------------------------------------------

.btn {
  border: none;
  color: $primary;
  font-weight: normal;
  background: $primary-low; 

  &[href] {
    color: $primary;
  }
  &:hover, &.btn-hover {
    background: $primary-medium; 
    color: $secondary;
  }
  &[disabled], &.disabled {
    background: $primary-low; 
    &:hover { color: dark-light-choose($primary-low-mid, $secondary-high); }
    cursor: not-allowed;
  }

  .d-icon {
    opacity: 0.7;
    line-height: $line-height-medium; // Match button text line-height 
  }
  &.btn-primary .d-icon {
    opacity: 1;
  }
}

// Primary button
// --------------------------------------------------

.btn-primary {
  border: none;
  font-weight: normal;
  color: $secondary;
  background: $tertiary;

  &[href] {
    color: $secondary;
  }
  &:hover, &.btn-hover {
    color: #fff;
    background: dark-light-choose($tertiary, $tertiary);
  }
  &:active, &.btn-active {
    @include linear-gradient($tertiary, $tertiary);
    color: $secondary;
  }
  &[disabled], &.disabled {
    background: $tertiary;
  }
}

// Danger button
// --------------------------------------------------

.btn-danger {
  color: $secondary;
  font-weight: normal;
  background: $danger;
  &[href] {
    color: $secondary;
  }
  &:hover, &.btn-hover {
    background: scale-color($danger, $lightness: -20%);
  }
  &:active, &.btn-active {
    @include linear-gradient(scale-color($danger, $lightness: -20%), $danger);
  }
  &[disabled], &.disabled {
    background: $danger;
  }
}

// Social buttons
// --------------------------------------------------

.btn-social {
  color: #fff;
  &:hover {
    color: #fff;
  }
  &[href] {
    color: $secondary;
  }
  &:before {
    margin-right: 9px;
    font-family: FontAwesome;
    font-size: $font-0;
  }
  &.google, &.google_oauth2 {
    background: $google;
    &:before {
      content: $fa-var-google;
    }
  }
  &.instagram {
    background: $instagram;
    &:before {
      content: $fa-var-instagram;
    }
  }
  &.facebook {
    background: $facebook;
    &:before {
      content: $fa-var-facebook;
    }
  }
  &.cas {
    background: $cas;
  }
  &.twitter {
    background: $twitter;
    &:before {
      content: $fa-var-twitter;
    }
  }
  &.yahoo {
    background: $yahoo;
    &:before {
      content: $fa-var-yahoo;
    }
  }
  &.github {
    background: $github;
    &:before {
      content: $fa-var-github;
    }
  }
}

// Button Sizes
// --------------------------------------------------

// Small

.btn-small {
  padding: 3px 6px;
  font-size: $font-down-1;
}

// Large

.btn-large {
  padding: 9px 18px;
  font-size: $font-up-1;
  line-height: $line-height-small;
}

.btn-flat {
  background: transparent;
  border: 0;
  outline: 0;
  line-height: $line-height-small;
  .d-icon {
    opacity: 0.7;
  }
}