diff --git a/src/kaleidoscope/device/keyboardio/Atreus2.cpp b/src/kaleidoscope/device/keyboardio/Atreus2.cpp
index 1bf38642..d5eb707f 100644
--- a/src/kaleidoscope/device/keyboardio/Atreus2.cpp
+++ b/src/kaleidoscope/device/keyboardio/Atreus2.cpp
@@ -1,6 +1,6 @@
 /* -*- mode: c++ -*-
  * Keyboardio Atreus hardware support for Kaleidoscope
- * Copyright (C) 2019  Keyboard.io, Inc
+ * Copyright (C) 2019, 2020  Keyboard.io, Inc
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -22,8 +22,11 @@
 #include "kaleidoscope/Runtime.h"
 #include "kaleidoscope/driver/keyscanner/Base_Impl.h"
 
+// We're using the `kaleidoscope::device::keyboardio` namespace, and set up the
+// aliases here, so that they're in the global namespace, within the scope of
+// this file. We do that, because of how templates are resolved and evaluated,
+// see more just down below!
 using namespace kaleidoscope::device::keyboardio;
-
 using KeyScannerProps = typename AtreusProps::KeyScannerProps;
 using KeyScanner = typename AtreusProps::KeyScanner;
 
@@ -31,17 +34,34 @@ namespace kaleidoscope {
 namespace device {
 namespace keyboardio {
 
+// `KeyScannerProps` here refers to the alias set up above. We do not need to
+// prefix the `matrix_rows` and `matrix_columns` names within the array
+// declaration, because those are resolved within the context of the class, so
+// the `matrix_rows` in `KeyScannerProps::matrix_row_pins[matrix_rows]` gets
+// resolved as `KeyScannerProps::matrix_rows`.
 const uint8_t KeyScannerProps::matrix_rows;
 const uint8_t KeyScannerProps::matrix_columns;
-
 constexpr uint8_t KeyScannerProps::matrix_row_pins[matrix_rows];
 constexpr uint8_t KeyScannerProps::matrix_col_pins[matrix_columns];
 
+// Resolving is a bit different in case of templates, however: the name of the
+// array is resolved within the scope of the namespace and the class, but the
+// array size is not - because it is a template. Therefore, we need a fully
+// qualified name there - or an alias in the global scope, which we set up just
+// above.
 template<> uint16_t KeyScanner::previousKeyState_[KeyScannerProps::matrix_rows] = {};
 template<> uint16_t KeyScanner::keyState_[KeyScannerProps::matrix_rows] = {};
 template<> uint16_t KeyScanner::masks_[KeyScannerProps::matrix_rows] = {};
 template<> uint8_t KeyScanner::debounce_matrix_[KeyScannerProps::matrix_rows][KeyScannerProps::matrix_columns] = {};
 
+// We set up the TIMER1 interrupt vector here. Due to dependency reasons, this
+// cannot be in a header-only driver, and must be placed here.
+//
+// Timer1 is responsible for setting a property on the KeyScanner, which will
+// tell it to do a scan. We use this to make sure that scans happen at roughly
+// the intervals we want. We do the scan outside of the interrupt scope for
+// practical reasons: guarding every codepath against interrupts that can be
+// reached from the scan is far too tedious, for very little gain.
 ISR(TIMER1_OVF_vect) {
   Runtime.device().keyScanner().do_scan_ = true;
 }