diff --git a/beginner/apps/.cargo/config.toml b/beginner/apps/.cargo/config.toml
index 7a1c918..4b518a8 100644
--- a/beginner/apps/.cargo/config.toml
+++ b/beginner/apps/.cargo/config.toml
@@ -6,6 +6,8 @@ rustflags = [
 ]
 
 [target.thumbv7em-none-eabihf]
+# set custom cargo runner to flash & run on embedded target when we call `cargo run`
+# for more information, check out https://github.com/knurling-rs/probe-run
 runner = "probe-run --chip nRF52840_xxAA"
 rustflags = [
   "-C", "link-arg=-Tlink.x",