implement tile movement

style/main.scss

@@ -14,6 +14,8 @@ $tile-color: #eee4da;
 $tile-gold-color: #edc22e;
 $tile-gold-glow-color: lighten($tile-gold-color, 15%);
 
+$transition-speed: 100ms;
+
 html, body {
   margin: 0;
   padding: 0;
@@ -132,7 +134,7 @@ hr {
   font-size: 55px;
   font-weight: bold;
 
-  @include transition(200ms ease);
+  @include transition($transition-speed ease-in-out);
   @include transition-property(top, left);
 
   // Build position classes
@@ -205,6 +207,23 @@ hr {
   }
 }
 
+@include keyframes(appear) {
+  0% {
+    -webkit-transform: scale(1.5);
+    opacity: 0;
+  }
+
+  100% {
+    -webkit-transform: scale(1);
+    opacity: 1;
+  }
+}
+
+.tile-new {
+  @include animation(appear 200ms ease $transition-speed);
+  @include animation-fill-mode(both);
+}
+
 .game-intro {
   margin-bottom: 0;
 }