Add improvements

src/styles/index.scss

@@ -11,8 +11,7 @@ $breakpoint: 800px;
 }
 
 html,
-body,
-canvas#main {
+body {
   height: 100%;
   width: 100%;
   overflow: hidden;
@@ -50,7 +49,7 @@ body {
       padding-top: 2px;
     }
 
-    img {
+    .logo {
       @include square(64px);
       padding-left: 8px;
     }
@@ -58,12 +57,33 @@ body {
     @media (max-width: $breakpoint) {
       font-size: 2rem;
 
-      img {
+      .logo {
         @include square(40px);
       }
     }
   }
 
+  #canvas-container {
+    &,
+    canvas {
+      position: absolute;
+      top: 0;
+      left: 0;
+      width: 100%;
+      height: 100%;
+    }
+
+    .full-screen-control {
+      position: absolute;
+      right: 0;
+      bottom: 0;
+      box-sizing: content-box;
+      @include square(40px);
+      padding: 16px;
+      cursor: pointer;
+    }
+  }
+
   #overlay {
     right: 0;
     white-space: pre-wrap;