Add sass

sass/base/_base.sass

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+// -----------------------------------------------------------------------------
+// This file contains very basic styles.
+// -----------------------------------------------------------------------------
+
+/**
+ * Set up a decent box model on the root element
+ */
+html {
+  box-sizing: border-box;
+}
+
+/**
+ * Make all elements from the DOM inherit from the parent box-sizing
+ * Since `*` has a specificity of 0, it does not override the `html` value
+ * making all elements inheriting from the root box-sizing value
+ * See: https://css-tricks.com/inheriting-box-sizing-probably-slightly-better-best-practice/
+ */
+*,
+*::before,
+*::after {
+  box-sizing: inherit;
+}
+
+/**
+ * Basic styles for links
+ */
+a {
+  color: $brand-color;
+  text-decoration: none;
+
+  @include on-event {
+    color: $text-color;
+    text-decoration: underline;
+  }
+}

sass/base/_fonts.sass

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+// -----------------------------------------------------------------------------
+// This file contains all @font-face declarations, if any.
+// -----------------------------------------------------------------------------

sass/base/_helpers.sass

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+// -----------------------------------------------------------------------------
+// This file contains CSS helper classes.
+// -----------------------------------------------------------------------------
+
+/**
+ * Clear inner floats
+ */
+.clearfix::after {
+  clear: both;
+  content: '';
+  display: table;
+}
+
+/**
+ * Main content containers
+ * 1. Make the container full-width with a maximum width
+ * 2. Center it in the viewport
+ * 3. Leave some space on the edges, especially valuable on small screens
+ */
+.container {
+  max-width: $max-width; /* 1 */
+  margin-left: auto; /* 2 */
+  margin-right: auto; /* 2 */
+  padding-left: 20px; /* 3 */
+  padding-right: 20px; /* 3 */
+  width: 100%; /* 1 */
+ }
+
+/**
+ * Hide text while making it readable for screen readers
+ * 1. Needed in WebKit-based browsers because of an implementation bug;
+ *    See: https://code.google.com/p/chromium/issues/detail?id=457146
+ */
+.hide-text {
+  overflow: hidden;
+  padding: 0; /* 1 */
+  text-indent: 101%;
+  white-space: nowrap;
+}
+
+/**
+ * Hide element while making it readable for screen readers
+ * Shamelessly borrowed from HTML5Boilerplate:
+ * https://github.com/h5bp/html5-boilerplate/blob/master/src/css/main.css#L119-L133
+ */
+.visually-hidden {
+  border: 0;
+  clip: rect(0 0 0 0);
+  height: 1px;
+  margin: -1px;
+  overflow: hidden;
+  padding: 0;
+  position: absolute;
+  width: 1px;
+}

sass/base/_typography.sass

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+/**
+ * Basic typography style for copy text
+ */
+body {
+  color: $text-color;
+  font: normal 125% / 1.4 $text-font-stack;
+}