Clean up and reorganize css

_sass/markdown.scss

@@ -0,0 +1,17 @@
+.markdown-body {
+  h1 { @include alt-h1; }
+  h2 { @include alt-h2; }
+  h3 { @include alt-h3; }
+
+  h1, h2, h3 {
+    margin-top: $spacer-6;
+
+    &:first-child {
+      margin-top: 0;
+    }
+  }
+
+  p {
+    color: $text-gray;
+  }
+}

_sass/pages/home.scss

@@ -0,0 +1,21 @@
+.timeline-comment {
+  position: relative;
+}
+
+.timeline-comment:before {
+    border-width: 8px;
+    border-right-color: #d1d5da;
+}
+.timeline-comment:after {
+    position: absolute;
+    top: 11px;
+    right: 100%;
+    left: -16px;
+    display: block;
+    width: 0;
+    height: 0;
+    pointer-events: none;
+    content: " ";
+    border-color: transparent;
+    border-style: solid solid outset;
+}

_sass/switcher.scss

@@ -0,0 +1,31 @@
+.sixteen-by-nine {
+  position: relative;
+
+  &:before {
+    display: block;
+    content: "";
+    width: 100%;
+    padding-top: (9 / 16) * 100%;
+  }
+
+  > .content {
+    position: absolute;
+    top: 0;
+    left: 0;
+    right: 0;
+    bottom: 0;
+  }
+}
+
+.switcher-input {
+  display: none;
+}
+
+.switcher-item {
+  transition: opacity .15s ease-in-out;
+  opacity: 0;
+
+  input:checked + & {
+    opacity: 1;
+  }
+}