diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index c9911d8..e02128c 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -1,15 +1,15 @@
 name: Builds the website (doesn't deploy - only used for checking syntax)
 
-on:
+on:  # yamllint disable-line rule:truthy
   push
 
 jobs:
   build-deploy:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
-    - name: Install the tutorial_web binary
-      run: /usr/bin/env python3 install.py linux
-    # Build the website
-    - name: Build
-      run: ./bin/tutorial_web build -i courses -s ./bin/static -o build -b /tutorial_web_content
+      - uses: actions/checkout@master
+      - name: Install the tutorial_web binary
+        run: /usr/bin/env python3 install.py linux
+      # Build the website
+      - name: Build
+        run: ./bin/tutorial_web build -i courses -s ./bin/static -o build -b /tutorial_web_content
diff --git a/.github/workflows/github_pages_deploy.yml b/.github/workflows/github_pages_deploy.yml
index 60fa61b..2d0560d 100644
--- a/.github/workflows/github_pages_deploy.yml
+++ b/.github/workflows/github_pages_deploy.yml
@@ -1,22 +1,22 @@
 name: Deploy to GH pages
 
-on:
+on:  # yamllint disable-line rule:truthy
   push:
     branches:
-    - master
+      - master
 
 jobs:
   build-deploy:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
-    - name: Install the tutorial_web binary
-      run: /usr/bin/env python3 install.py linux
-    # Build the website
-    - name: Build
-      run: ./bin/tutorial_web build -i courses -s ./bin/static -o build -b /tutorial_web_content
-    - name: Deploy
-      uses: JamesIves/github-pages-deploy-action@4.1.5
-      with:
-        branch: gh-pages
-        folder: build
+      - uses: actions/checkout@master
+      - name: Install the tutorial_web binary
+        run: /usr/bin/env python3 install.py linux
+      # Build the website
+      - name: Build
+        run: ./bin/tutorial_web build -i courses -s ./bin/static -o build -b /tutorial_web_content
+      - name: Deploy
+        uses: JamesIves/github-pages-deploy-action@4.1.5
+        with:
+          branch: gh-pages
+          folder: build
diff --git a/.github/workflows/yaml_lint.yaml b/.github/workflows/yaml_lint.yaml
new file mode 100644
index 0000000..a3cea23
--- /dev/null
+++ b/.github/workflows/yaml_lint.yaml
@@ -0,0 +1,17 @@
+name: YAML Lint
+
+on:  # yamllint disable-line rule:truthy
+  push
+
+jobs:
+  yamllint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: YAML Lint
+        uses: ibiqlik/action-yamllint@v3
+        with:
+          file_or_dir: .
+          config_file: .yamllint.yaml
diff --git a/.yamllint.yaml b/.yamllint.yaml
new file mode 100644
index 0000000..8d5386a
--- /dev/null
+++ b/.yamllint.yaml
@@ -0,0 +1,15 @@
+extends: default
+
+ignore: |
+  .git/**
+rules:
+  braces:
+    level: error
+    max-spaces-inside: 1
+  brackets:
+    level: error
+    max-spaces-inside: 1
+  document-start: disable
+  line-length: disable
+  new-line-at-end-of-file: enable
+  trailing-spaces: enable
diff --git a/courses/scratch/ghostcatcher.yml b/courses/scratch/ghostcatcher.yml
index 8f64449..33960cb 100644
--- a/courses/scratch/ghostcatcher.yml
+++ b/courses/scratch/ghostcatcher.yml
@@ -49,8 +49,8 @@ tutorials:
       Click on the Paint Tool, select a color you like and click on the checkered area to paint it.
 
       ![](assets/color_selector_paint_tool.png)
-      
-      Feel free to experiment with the other tools, but don't make it too crowded just yet! 
+
+      Feel free to experiment with the other tools, but don't make it too crowded just yet!
       You can come back later and improve the background, or select a completely new one.
 
   - subtitle: Drawing Pacman
@@ -115,7 +115,7 @@ tutorials:
     content: |
       Let's go to the "Code" tab and start animating Pacman!
       Click on the "Events" section on the left and find the block labelled
-      `When [green flag] pressed`. Click and drag the block from the left 
+      `When [green flag] pressed`. Click and drag the block from the left
       onto the right hand screen.
 
       ![](assets/pacman_green_flag.png)
@@ -165,7 +165,7 @@ tutorials:
       ![](assets/no_outline.png)
 
       Let's draw a circle and a square on top of it.
-      
+
       ![](assets/circle_and_square_for_ghost.png)
 
       You can draw the ghost's legs by erasing two triangles from the bottom
@@ -188,7 +188,7 @@ tutorials:
       Feel free to come to this section later if you want to go straight to continuing with the game.
 
       Let's make an animated ghost just like we did for pacman.
-      
+
       Duplicate the costume ghost.
 
       Click on the black ovan inside the eye.
diff --git a/courses/web/cookie_clicker.yml b/courses/web/cookie_clicker.yml
index e5d41fd..5247a14 100644
--- a/courses/web/cookie_clicker.yml
+++ b/courses/web/cookie_clicker.yml
@@ -64,7 +64,7 @@ tutorials:
 
       ## Tasks
 
-      Have a look at the line in the HTML that says: 
+      Have a look at the line in the HTML that says:
       ```html
       <!-- Task: replace this comment with an image take that displays an image a cookie -->
       ```
@@ -314,4 +314,3 @@ tutorials:
       - It would be nice to see how many factories/chefs/bakeries you have purchased and how many they
         produce per second.
       - Upgrades. You could create purchasable upgrades to improve the productivity of your cookie production.
-