Fix build

.gitignore

@@ -3,5 +3,4 @@
 _site/
 .sass-cache/
 .jekyll-metadata
-assets/
 

docs/assets/core.scss

@@ -0,0 +1,5 @@
+---
+# Front matter comment to ensure Jekyll properly reads file.
+---
+
+@import 'main';

docs/assets/main.js

@@ -0,0 +1,29 @@
+(function (document) {
+  document.addEventListener('DOMContentLoaded', function () {
+
+    var switcher = document.querySelector('#color-switcher')
+    var html = document.querySelector('html')
+    var images = document.querySelectorAll('.image-switchable')
+
+    switcher.addEventListener('click', function () {
+      // Reload images:
+      for (var i = 0; i < images.length; i++) {
+        var srcNext = images[i].getAttribute('data-src')
+        var srcCurrent = images[i].getAttribute('src')
+        images[i].setAttribute('src', srcNext)
+        images[i].setAttribute('data-src', srcCurrent)
+      }
+
+      // Toggle styles:
+      html.classList.toggle('dark-mode')
+      html.classList.toggle('white-mode')
+
+      // Set button text:
+      var textNext = switcher.getAttribute('data-text')
+      var textCurrent = switcher.innerText
+
+      switcher.innerText = textNext
+      switcher.setAttribute('data-text', textCurrent)
+    })
+  })
+})(document)