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@import "global";
@import "compass/utilities/general/hacks";
@import "compass/css3/images";
@import "compass/css3/text-shadow";
@import "compass/css3/box-sizing";

$include-html-button-with-gradient-classes: $include-html-classes !default;

$font-color-dark: #555 !default;
$font-color-light: #fff !default;

// btn gradient color definition.
$default-color-start: #f3f3f3 !default;
$primary-color-start: #3fbcb5 !default;


// We use these to control gradient stop color and hover effects.
$btn-bg-color-stop-factor: -10% !default;
$btn-bg-color-hover-factor: -5% !default;

// We use these to control gradient and border colors.
$btn-bg-color-start: $default-color-start !default;
$btn-bg-color-stop: scale-color($btn-bg-color-start, $lightness:$btn-bg-color-stop-factor) !default;
$btn-bg-color-start-hover: scale-color($btn-bg-color-start, $lightness:$btn-bg-color-hover-factor) !default;
$btn-bg-color-stop-hover: scale-color($btn-bg-color-start-hover, $lightness:$btn-bg-color-stop-factor) !default;
$btn-default-border-color: $btn-bg-color-start-hover !default;
$btn-default-border-color-hover: scale-color($btn-bg-color-stop-hover, $lightness:$btn-bg-color-hover-factor) !default;
$btn-default-text-shadow-color: $btn-bg-color-start-hover !default;

$btn-primary-bg-color-start: $primary-color-start;
$btn-primary-bg-color-stop: scale-color($btn-primary-bg-color-start, $lightness:$btn-bg-color-stop-factor) !default;
$btn-primary-bg-color-start-hover: scale-color($primary-color-start, $lightness:$btn-bg-color-hover-factor) !default;
$btn-primary-bg-color-stop-hover: scale-color($btn-primary-bg-color-start-hover, $lightness:$btn-bg-color-stop-factor) !default;
$btn-primary-border-color: $btn-primary-bg-color-start-hover !default;
$btn-primary-border-color-hover: scale-color($btn-primary-bg-color-stop-hover, $lightness:$btn-bg-color-hover-factor) !default;
$btn-primary-text-shadow-color: $btn-primary-bg-color-start-hover !default;

// @MIXIN

// We use this mixin for dynamic generate gradient btns.
// If you want disable this mixin, please set $color-start to false;

@mixin btn-gradinet-style($color-start:$btn-bg-color-start, $color-stop:null, $color-start-hover:null, $color-stop-hover:null, $border-color:null, $border-color-hover:null, $text-shadow-color:null) {

	@if $color-start {
		@if $color-stop == null {
			$color-stop: if($color-start == $btn-bg-color-start, $btn-bg-color-stop, scale-color($color-start, $lightness:$btn-bg-color-stop-factor));
		}
		@if $color-start-hover == null {
			$color-start-hover: if($color-start == $btn-bg-color-start, $btn-bg-color-start-hover, scale-color($color-start, $lightness:$btn-bg-color-hover-factor));
		}
		@if $color-stop-hover == null {
			$color-stop-hover: if($color-start == $btn-bg-color-start, $btn-bg-color-stop-hover, scale-color($color-start-hover, $lightness:$btn-bg-color-stop-factor));
		}
		@if $border-color == null {
			$border-color: if($color-start == $btn-bg-color-start, $btn-default-border-color, scale-color($color-start, $lightness:$btn-bg-color-hover-factor));
		}
		@if $border-color-hover == null {
			$border-color-hover: if($color-start == $btn-bg-color-start, $btn-default-border-color-hover, scale-color($color-start-hover, $lightness:$btn-bg-color-hover-factor));
		}
		@if $text-shadow-color == null {
			$text-shadow-color: if($color-start == $btn-bg-color-start, $btn-default-text-shadow-color, scale-color($color-start, $lightness:$btn-bg-color-hover-factor));
		}
	}

	$bg-lightness: lightness($color-start);
    	$bg-hover-lightness: lightness($color-start-hover);

	background-color: $color-start;
	@include background(linear-gradient($color-start, $color-stop));
	@include filter-gradient($color-start, $color-stop);
	@include single-text-shadow($hoff:-1px, $voff:-1px, $blur:0, $color:$text-shadow-color);
	border-width: 1px;
	border-style: solid;
	border-color: $border-color;
	color: if($bg-lightness > 70%, $font-color-dark, $font-color-light);

	@include single-transition(all);
	@include box-sizing(border-box);

	&:hover,
	&:focus {
		background-color: $color-start-hover;
		@include background(linear-gradient($color-start-hover, $color-stop-hover));
		@include filter-gradient($color-start, $color-stop-hover);
		border-color: $border-color-hover;
		color: if($bg-hover-lightness > 70%, $font-color-dark, $font-color-light);
	}

}

@mixin btn-gradient($color-start:$btn-bg-color-start, $color-stop:null, $color-start-hover:null, $color-stop-hover:null, $border-color:null, $border-color-hover:null, $text-shadow-color:null) {
  @include btn-gradinet-style($color-start, $color-stop, $color-start-hover, $color-stop-hover, $border-color, $border-color-hover, $text-shadow-color);

  @if $transition {
    @include single-transition(all);
  }
}

@include exports("gradient-btn") {
 	@if $include-html-button-with-gradient-classes {
 		.default-gradient-btn {
 			@include btn-gradinet-style;

 			@include single-transition(all);	
 		}
 		.primary-gradient-btn {
 			@include btn-gradinet-style($color-start:$btn-primary-bg-color-start, $color-stop:$btn-primary-bg-color-stop, $color-start-hover:$btn-primary-bg-color-start-hover, $color-stop-hover:$btn-primary-bg-color-stop-hover, $border-color:$btn-primary-border-color, $border-color-hover:$btn-primary-border-color-hover, $text-shadow-color:$btn-primary-text-shadow-color);

 			@include single-transition(all);
 		}
 		.button-test {
 			@include btn-gradinet-style(#9b59b6);
 		}
 	}
 }
	

HOW TO USE ?

Please add this file in to your Foundation 5 project.
You must to add this file in to path_to_your_project/bower_components/foundation/scss

Next add this @import path to your _foundation.scss file. 
@import "foundation/components/buttons-with-gradient";

Please create your custom button .class and @include btn-gradient-style @mixin in _buttons-with-gradient.scss file. 
Set your $color-start value for example #e74c3c.

.button-test {
 	@include btn-gradinet-style(#e74c3c);
 }
 
 Use your .class in html or haml file. Don't forgot about add .button class. 
 
 <a href="#" class="button button-test"></a>