diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index 17e339c..aeaaf0d 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -51,12 +51,18 @@ jobs:
 
     - name: build tools
       working-directory: ./tools
-      run: cargo build --verbose
+      run: |
+        cargo build --verbose
+        cargo fmt --all -- --check
 
-    - name: build beginner/apps
+    - name: build and fmt beginner/apps
       working-directory: ./beginner/apps
-      run: cargo build --verbose
+      run: |
+        cargo build --verbose
+        cargo fmt --all -- --check
 
-    - name: build advanced/firmware
+    - name: build and fmt advanced/firmware
       working-directory: ./advanced/firmware
-      run: cargo build --verbose
+      run: |
+        cargo build --verbose
+        cargo fmt --all -- --check
\ No newline at end of file
diff --git a/advanced/firmware/src/bin/usb-2-solution.rs b/advanced/firmware/src/bin/usb-2-solution.rs
index 3f8cfe4..342472a 100644
--- a/advanced/firmware/src/bin/usb-2-solution.rs
+++ b/advanced/firmware/src/bin/usb-2-solution.rs
@@ -44,7 +44,6 @@ fn on_event(usbd: &USBD, event: Event) {
         Event::UsbEp0DataDone => todo!(),
 
         Event::UsbEp0Setup => {
-
             // the BMREQUESTTYPE register contains information about data recipient, transfer type and direction
             let bmrequesttype = usbd.bmrequesttype.read().bits() as u8;
             // the BREQUEST register stores the type of the current request (e.g. SET_ADDRESS, GET_DESCRIPTOR, ...)
diff --git a/embedded-workshop-book/src/radio-puzzle-help.md b/embedded-workshop-book/src/radio-puzzle-help.md
index d4654ec..eba85a8 100644
--- a/embedded-workshop-book/src/radio-puzzle-help.md
+++ b/embedded-workshop-book/src/radio-puzzle-help.md
@@ -17,16 +17,18 @@ use heapless::consts::*;   // defines U16, U32, U64... etc. to set the size of t
 
 fn main() {
     // A hash map with a capacity of 16 key-value pairs allocated on the stack
+    // note that U16 is a heapless constant, not Rust's u16
     let mut my_map = FnvIndexMap::<_, _, U16>::new();
     my_map.insert(b'A', b'~').unwrap();
 
     // A vector with a fixed capacity of 8 elements allocated on the stack
+    // note that U8 is a heapless constant, not Rust's u8
     let mut my_vec = Vec::<_, U8>::new();
     my_vec.push(b'A').unwrap();
 }
 ```
 
-If you haven't used a stack-allocated collection before note that you'll need to specify the capacity of the collection as a type parameter using one of the "type-level values" in the `heapless::consts` module. The [`heapless::IndexMap` documentation][indexMap] of the `heapless` crate has some usage examples, as does the [`heapless::Vec` documentation][vec].
+If you haven't used a stack-allocated collection before note that you'll need to specify the capacity of the collection as a type parameter using one of the "type-level values" in the `heapless::consts` module (e.g. `U8`, `U64` etc.). The [`heapless::IndexMap` documentation][indexMap] of the `heapless` crate has some usage examples, as does the [`heapless::Vec` documentation][vec].
 
 [indexMap]: https://docs.rs/heapless/0.5.5/heapless/struct.IndexMap.html
 [vec]: https://docs.rs/heapless/0.5.5/heapless/struct.Vec.html