diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..75f0164
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+# Ignore NPM dependencies
+node_modules/
+package-lock.json
+
+# Ignore build process output
+dist/
diff --git a/gulpfile.js b/gulpfile.js
new file mode 100644
index 0000000..71aaaae
--- /dev/null
+++ b/gulpfile.js
@@ -0,0 +1,60 @@
+/**
+ * The Gulpfile is the file that tells the task runner, Gulp, what to do.
+ *
+ * The file is split up into a series of tasks. The task named 'default' will
+ * be executed when the command 'gulp' is run on the command line. The NPM
+ * script 'build' (defined in package.json) will run gulp to build the project.
+ *
+ * Gulp.js: https://gulpjs.com/
+ */
+
+const gulp = require("gulp")
+const del = require("del")
+const postcss = require("gulp-postcss")
+
+/**
+ * Removes any previous builds from the distribution directory.
+ */
+gulp.task('clean', async done => {
+  await del("./dist/")
+  done()
+})
+
+/**
+ * Copies legacy pre-built CSS files from older versions of the codebase
+ * directly to the distribution directory.
+ */
+gulp.task('legacy', () => {
+  return gulp.src("./legacy/*.css").pipe(gulp.dest("./dist/css/min/"))
+})
+
+/**
+ * Takes CSS files, minifies them, and outputs them to dist/.
+ *
+ * This task uses PostCSS, which is a CSS plugin that can be configured to do
+ * many different things. PostCSS is configured in postcss.config.js.
+ *
+ * PostCSS: https://postcss.org/
+ * PostCSS plugins: https://www.postcss.parts/
+ */
+gulp.task('css', () => {
+  return gulp
+    .src("./src/**/*.css")
+    .pipe(postcss())
+    .pipe(gulp.dest("./dist/"))
+})
+
+/**
+ * Copies other files from src/ to dist/, which makes them available for
+ * deployment.
+ */
+gulp.task('files', () => {
+  return gulp
+    .src(["./src/**/*", "!./src/**/*.css"])
+    .pipe(gulp.dest("./dist/"))
+})
+
+/**
+ * Runs all tasks in order.
+ */
+gulp.task('default', gulp.series('clean', 'files', 'legacy', 'css'))
diff --git a/docs/css/min/Common-Theme-Dark-Mode-1.0.min.css b/legacy/Common-Theme-Dark-Mode-1.0.min.css
similarity index 100%
rename from docs/css/min/Common-Theme-Dark-Mode-1.0.min.css
rename to legacy/Common-Theme-Dark-Mode-1.0.min.css
diff --git a/docs/css/min/Common-Theme-Extension_BHL-Compatibilizer-1.0.min.css b/legacy/Common-Theme-Extension_BHL-Compatibilizer-1.0.min.css
similarity index 100%
rename from docs/css/min/Common-Theme-Extension_BHL-Compatibilizer-1.0.min.css
rename to legacy/Common-Theme-Extension_BHL-Compatibilizer-1.0.min.css
diff --git a/docs/css/min/Common-Theme-Extension_Forum-enhancements-1.0.min.css b/legacy/Common-Theme-Extension_Forum-enhancements-1.0.min.css
similarity index 100%
rename from docs/css/min/Common-Theme-Extension_Forum-enhancements-1.0.min.css
rename to legacy/Common-Theme-Extension_Forum-enhancements-1.0.min.css
diff --git a/docs/css/min/Sigma-9-Common-Sandbox-Theme-1.0.min.css b/legacy/Sigma-9-Common-Sandbox-Theme-1.0.min.css
similarity index 100%
rename from docs/css/min/Sigma-9-Common-Sandbox-Theme-1.0.min.css
rename to legacy/Sigma-9-Common-Sandbox-Theme-1.0.min.css
diff --git a/docs/css/min/Sigma-9-Common-Sandbox-Theme-1.1.min.css b/legacy/Sigma-9-Common-Sandbox-Theme-1.1.min.css
similarity index 100%
rename from docs/css/min/Sigma-9-Common-Sandbox-Theme-1.1.min.css
rename to legacy/Sigma-9-Common-Sandbox-Theme-1.1.min.css
diff --git a/docs/css/min/Sigma-9-Common-Theme-1.3.7.min.css b/legacy/Sigma-9-Common-Theme-1.3.7.min.css
similarity index 100%
rename from docs/css/min/Sigma-9-Common-Theme-1.3.7.min.css
rename to legacy/Sigma-9-Common-Theme-1.3.7.min.css
diff --git a/docs/css/min/Sigma-9-Common-Theme-1.3.8.min.css b/legacy/Sigma-9-Common-Theme-1.3.8.min.css
similarity index 100%
rename from docs/css/min/Sigma-9-Common-Theme-1.3.8.min.css
rename to legacy/Sigma-9-Common-Theme-1.3.8.min.css
diff --git a/docs/css/min/Sigma-9-Common-Theme-1.3.min.css b/legacy/Sigma-9-Common-Theme-1.3.min.css
similarity index 100%
rename from docs/css/min/Sigma-9-Common-Theme-1.3.min.css
rename to legacy/Sigma-9-Common-Theme-1.3.min.css
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..97c403b
--- /dev/null
+++ b/package.json
@@ -0,0 +1,12 @@
+{
+  "name": "common-theme",
+  "scripts": {
+    "build": "gulp"
+  },
+  "devDependencies": {
+    "del": "^6.0.0",
+    "gulp": "^4.0.2",
+    "gulp-postcss": "^9.0.0",
+    "postcss": "^8.2.4"
+  }
+}
diff --git a/postcss.config.js b/postcss.config.js
new file mode 100644
index 0000000..b5bc014
--- /dev/null
+++ b/postcss.config.js
@@ -0,0 +1,6 @@
+/**
+ * PostCSS configuration
+ */
+module.exports = {
+  plugins: []
+}
diff --git a/docs/css/Patch-CT-1.3-Hotfix.css b/src/css/Patch-CT-1.3-Hotfix.css
similarity index 100%
rename from docs/css/Patch-CT-1.3-Hotfix.css
rename to src/css/Patch-CT-1.3-Hotfix.css
diff --git a/docs/css/Sigma-9-Common-Theme-LATEST.css b/src/css/Sigma-9-Common-Theme-LATEST.css
similarity index 100%
rename from docs/css/Sigma-9-Common-Theme-LATEST.css
rename to src/css/Sigma-9-Common-Theme-LATEST.css
diff --git a/docs/css/Sigma-9-Common-Theme-STABLE.css b/src/css/Sigma-9-Common-Theme-STABLE.css
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rename from docs/css/Sigma-9-Common-Theme-STABLE.css
rename to src/css/Sigma-9-Common-Theme-STABLE.css
diff --git a/docs/css/de/Common-Theme-DE-Edition.css b/src/css/de/Common-Theme-DE-Edition.css
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rename from docs/css/de/Common-Theme-DE-Edition.css
rename to src/css/de/Common-Theme-DE-Edition.css
diff --git a/docs/css/de/Common-Theme-DE-O5-Edition.css b/src/css/de/Common-Theme-DE-O5-Edition.css
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rename from docs/css/de/Common-Theme-DE-O5-Edition.css
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diff --git a/docs/css/de/Common-Theme-DE-Sandbox-Edition.css b/src/css/de/Common-Theme-DE-Sandbox-Edition.css
similarity index 100%
rename from docs/css/de/Common-Theme-DE-Sandbox-Edition.css
rename to src/css/de/Common-Theme-DE-Sandbox-Edition.css
diff --git a/docs/css/int/Common-Theme-INT-Edition.css b/src/css/int/Common-Theme-INT-Edition.css
similarity index 100%
rename from docs/css/int/Common-Theme-INT-Edition.css
rename to src/css/int/Common-Theme-INT-Edition.css
diff --git a/docs/css/int/Common-Theme-INT-Sandbox-Edition.css b/src/css/int/Common-Theme-INT-Sandbox-Edition.css
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rename from docs/css/int/Common-Theme-INT-Sandbox-Edition.css
rename to src/css/int/Common-Theme-INT-Sandbox-Edition.css
diff --git a/docs/font/font-awesome.min.css b/src/font/font-awesome.min.css
similarity index 100%
rename from docs/font/font-awesome.min.css
rename to src/font/font-awesome.min.css
diff --git a/docs/font/font-bauhaus.css b/src/font/font-bauhaus.css
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rename from docs/font/font-bauhaus.css
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diff --git a/docs/font/fontawesome-webfont.eot b/src/font/fontawesome-webfont.eot
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diff --git a/docs/font/fontawesome-webfont.ttf b/src/font/fontawesome-webfont.ttf
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diff --git a/docs/font/fontawesome-webfont.woff b/src/font/fontawesome-webfont.woff
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diff --git a/docs/font/fontawesome-webfont.woff2 b/src/font/fontawesome-webfont.woff2
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diff --git a/docs/font/itc-bauhaus-lt-demi.eot b/src/font/itc-bauhaus-lt-demi.eot
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diff --git a/docs/img/body_bg.png b/src/img/body_bg.png
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diff --git a/docs/img/expand.png b/src/img/expand.png
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diff --git a/docs/img/home.png b/src/img/home.png
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diff --git a/docs/img/home_fff.png b/src/img/home_fff.png
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diff --git a/docs/img/int/body_bg_int.png b/src/img/int/body_bg_int.png
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diff --git a/docs/img/int/don't.delete b/src/img/int/don't.delete
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diff --git a/docs/img/open-menu-button.png b/src/img/open-menu-button.png
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diff --git a/docs/img/yuitabs.png b/src/img/yuitabs.png
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diff --git a/docs/svg/SVG-Notes.txt b/src/svg/SVG-Notes.txt
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