ionic-framework/ionic/components/button/button.scss

// Core Button Variables
// --------------------------------------------------

$button-font-size:                1.6rem !default;
$button-margin:                   0.4rem 0 !default;
$button-padding:                  0 2rem !default;
$button-height:                   4.4rem !default;
$button-border-width:             1px !default;
$button-border-radius:            4px !default;
$button-icon-size:                2.5rem !default;

$button-large-font-size:          2rem !default;
$button-large-height:             5.4rem !default;
$button-large-padding:            1.4rem !default;
$button-large-icon-size:          3.6rem !default;

$button-small-font-size:          1.3rem !default;
$button-small-height:             2.8rem !default;
$button-small-padding:            1.1rem !default;
$button-small-icon-size:          2.1rem !default;

$button-fab-size:                 56px;

$button-round-border-radius:      64px !default;
$button-round-padding:            0 2.6rem !default;


// Core Button
// --------------------------------------------------

button,
[button] {
  position: relative;
  display: inline-flex;
  flex-shrink: 0;
  flex-flow: row nowrap;
  align-items: center;
  justify-content: center;

  will-change: transform;

  margin: $button-margin;
  line-height: 1.1;

  @include appearance(none);

  vertical-align: top; // the better option for most scenarios
  vertical-align: -webkit-baseline-middle; // the best for those that support it

  font-family: inherit;
  font-variant: inherit;
  font-style: inherit;

  white-space: nowrap;
  text-overflow: ellipsis;
  overflow: hidden;

  cursor: pointer;
  user-select: none;

  border: 1px solid #ccc;
  padding: $button-padding;
  min-height: $button-height;
  // Default button has no background
  background: transparent;

  text-align: center;
  font-size: $button-font-size;
  border: transparent;
  border-radius: $button-border-radius;

  &[icon] {
    font-size: $button-icon-size;
    background: none;
    border: none;
  }

  &[large] {
    padding: 0 $button-large-padding;
    min-width: ($button-large-padding * 4);
    min-height: $button-large-height;
    font-size: $button-large-font-size;

    &[icon] {
      font-size: $button-large-icon-size;
    }
  }

  &[small] {
    padding: 0 $button-small-padding;
    min-width: ($button-small-padding * 3);
    min-height: $button-small-height;
    font-size: $button-small-font-size;

    &[icon] {
      font-size: $button-small-icon-size;
    }
  }


  // Core Button Types
  // --------------------------------------------------

  &[clear] {
    border-color: transparent;
    background: none;
  }

  &[outline] {
    background: none;

    &.activated {
      opacity: 0.3 !important;
    }
  }

  &[block] {
    display: flex;
    clear: both;
    margin-right: 0;
    margin-left: 0;
    width: 100%;

    &:after {
      clear: both;
    }
  }

  &[full] {
    width: 100%;
    border-radius: 0;
  }

  &.disabled,
  &[disabled] {
    opacity: .4;
    cursor: default !important;
    pointer-events: none;
  }

  &[round] {
    border-radius: $button-round-border-radius;
    padding: $button-round-padding;
  }

  // FABulous buttons (Floating action button from material)

  &[fab] {
    position: absolute;
    width: $button-fab-size;
    height: $button-fab-size;
    line-height: $button-fab-size;
    min-width: 0;
    vertical-align: middle;

    border-radius: 50%;
    background-clip: padding-box;

    overflow: hidden;

    transition: .2s linear;
    transition-property: background-color;

    font-size: 14px;

    &[fab-center] {
      left: 50%;
      margin-left: -$button-fab-size/2;
    }
    &[fab-top] {
      top: 16px;
    }
    &[fab-right] {
      right: 16px;
    }
    &[fab-bottom] {
      bottom: 16px;
    }
    &[fab-left] {
      left: 16px;
    }

    .icon {
      flex: 1;
    }
  }
}

[full],
[full] > button,
[full] > [button] {
  display: flex;
  margin-right: 0;
  margin-left: 0;
  width: 100%;
  border-radius: 0;

  &[outline][outline] {
    border-right-width: 0;
    border-left-width: 0;
  }
}

.padding > button[block]:first-child,
.padding > [button][block]:first-child {
  margin-top: 0;
}

.icon-left:before {
  font-size: 1.5em;
  margin-top: -0.1em;
  margin-right: 0.25em;
}

.icon-right:before {
  order: 2;
  font-size: 1.5em;
  margin-top: -0.1em;
  margin-left: 0.25em;
}


// Button Misc
// --------------------------------------------------

a[button] {
  color: inherit;
  text-decoration: none;
}


// Core Button Mixins
// --------------------------------------------------

@mixin button-default($bg-color, $fg-color) {
  background-color: $bg-color;
  color: $fg-color;
  transition: background-color,opacity 100ms linear;

  &:hover,
  &.hover {
    opacity: 0.88;
    color: $fg-color;
    text-decoration: none;
  }

  &.activated {
    opacity: 1;
    background-color: darken($bg-color, 12%);
  }
}

@mixin button-clear($fg-color) {
  &[clear] {
    color: $fg-color;
    background: none;
  }
}

@mixin button-outline($fg-color) {
  &[outline] {
    border: 1px solid $fg-color;
    background: transparent;
    color: $fg-color;

    &.activated {
      color: white;
      background-color: rgb(red($fg-color), green($fg-color), blue($fg-color));//, 0.15);
    }
  }
}


// Core Button Color Generation
// --------------------------------------------------

@each $color, $value in $colors {

  button[#{$color}],
  [button][#{$color}] {

    @if lightness(get-color($color, base)) > 90 {
      $fg-color: get-color($color, inverse);
    } @else {
      $fg-color: get-color($color, base);
    }

    @include button-default(get-color($color, base),
                            get-color($color, inverse));

    @include button-clear($fg-color);

    @include button-outline(get-color($color, light));
  }

}