ionic-framework/scss/ionic/_button.scss

.button {
  position: relative;
  display: inline-block;
  margin: 0;
  padding: $button-padding;
  border-width: $button-border-width;
  border-style: solid;
  border-radius: $button-border-radius;
  color: $button-color;
  vertical-align: middle;
  text-align: center;
  font-size: $button-font-size;
  cursor: pointer;

  &.button-icon {
    border: none;
    background: none;
    padding: $button-clear-padding;
  }

  &.button-clear {
    border: none;
    background: none;
    box-shadow: none;

    // A nice iOS 7 style fade click
    @include transition(opacity .1s);

    &:active, &.active {
      opacity: 0.4;
    }
  }

  &.button-block {
    display: block;
    margin: $button-block-margin;
  }

  &.button-default {
    @include button-style($button-default-bg, $button-default-border, $button-default-active-bg, $button-default-active-border, $gray-dark);

    @include button-clear($gray-dark);
  }
  &.button-secondary {
    @include button-style($button-secondary-bg, $button-secondary-border, $button-secondary-active-bg, $button-secondary-active-border, $gray-dark);
    @include button-clear($gray-dark);
  }
  &.button-primary {
    @include button-style($button-primary-bg, $button-primary-border, $button-primary-active-bg, $button-primary-active-border, $white);
    @include button-clear($button-primary-bg);
  }
  &.button-info {
    @include button-style($button-info-bg, $button-info-border, $button-info-active-bg, $button-info-active-border, $white);
    @include button-clear($button-info-bg);
  }
  &.button-success {
    @include button-style($button-success-bg, $button-success-border, $button-success-active-bg, $button-success-active-border, $white);
    @include button-clear($button-success-bg);
  }
  &.button-warning {
    @include button-style($button-warning-bg, $button-warning-border, $button-warning-active-bg, $button-warning-active-border, $white);
    @include button-clear($button-warning-bg);
  }
  &.button-danger {
    @include button-style($button-danger-bg, $button-danger-border, $button-danger-active-bg, $button-danger-active-border, $white);
    @include button-clear($button-danger-bg);
  }
  &.button-dark {
    @include button-style($button-dark-bg, $button-dark-border, $button-dark-active-bg, $button-dark-active-border, $white);
    @include button-clear($button-dark-bg);
  }

  &.button-icon {
    border: none;
    background: none;
    &:active, &.active {
      text-shadow: 0px 0px 10px #fff;
      box-shadow: none;
      background: none;
    }
  }
}

a.button {
  text-decoration: none;
}

.button-transparent {
  background: transparent;
}

.button-clear [class^="icon-"] {
  font-size: 24px;  
}