diff --git a/_config.yml b/_config.yml
index 260c7fa..00879a9 100644
--- a/_config.yml
+++ b/_config.yml
@@ -42,6 +42,13 @@ url: "https://makeabilitylab.github.io" # the base hostname & protocol for your
 # For copy button on code
 enable_copy_code_button: true
 
+# Jekyll plugins. jekyll-sitemap generates /sitemap.xml (submittable to search
+# engines) to help indexing. It ships with the github-pages gem and is on the
+# GitHub Pages plugin whitelist, so it works under both the legacy build and the
+# GitHub Actions build (#98).
+plugins:
+  - jekyll-sitemap
+
 # custom site variables
 arduino_github_baseurl: "https://makeabilitylab.github.io/physcomp/"
 comments: false
diff --git a/advancedio/smoothing-input.md b/advancedio/smoothing-input.md
index c3cfa7c..76b6398 100644
--- a/advancedio/smoothing-input.md
+++ b/advancedio/smoothing-input.md
@@ -204,7 +204,7 @@ $$
 S_{i} =
 \begin{cases}
     X_{1} & \text{if i = 1}\\
-    \alpha \cdot X_{i} + (1 - \alpha) \cdot S_{i-1} & \text{if i $>$ 1}
+    \alpha \cdot X_{i} + (1 - \alpha) \cdot S_{i-1} & \text{if i > 1}
 \end{cases}
 $$
 
diff --git a/esp32/esp32-ide.md b/esp32/esp32-ide.md
index 345188d..c2bd86b 100644
--- a/esp32/esp32-ide.md
+++ b/esp32/esp32-ide.md
@@ -196,6 +196,9 @@ With your IDE set up, you're ready to start building ESP32 projects!
 
 Head back to [Lesson 1: Introduction to the ESP32](esp32.md) to learn about the hardware, or jump straight to [Lesson 2: Blinking an LED](led-blink.md) if you're ready to write code.
 
-<span class="fs-6">
-[Back to: Introduction to the ESP32](esp32.md){: .btn .btn-outline }
-</span>
\ No newline at end of file
+<nav class="lesson-nav" aria-label="Lesson navigation">
+  <a href="esp32.html" class="nav-prev">
+    <div class="nav-label">&larr; Previous Lesson</div>
+    <div class="nav-title">Introduction to the ESP32</div>
+  </a>
+</nav>
\ No newline at end of file
diff --git a/robots.txt b/robots.txt
new file mode 100644
index 0000000..872cd91
--- /dev/null
+++ b/robots.txt
@@ -0,0 +1,4 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://makeabilitylab.github.io/physcomp/sitemap.xml