diff --git a/matrix.hpp b/matrix.hpp
index 48a7d8f5..7a8b8b8f 100644
--- a/matrix.hpp
+++ b/matrix.hpp
@@ -14,8 +14,8 @@
  * Copyright 2011-2015 Danny Robson <danny@nerdcruft.net>
  */
 
-#ifndef __UTIL_MATRIX_HPP
-#define __UTIL_MATRIX_HPP
+#ifndef CRUFT_UTIL_MATRIX_HPP
+#define CRUFT_UTIL_MATRIX_HPP
 
 #include "point.hpp"
 #include "range.hpp"
@@ -26,6 +26,13 @@
 #include <ostream>
 
 namespace util {
+    ///////////////////////////////////////////////////////////////////////////
+    /// a row-major matrix with parameterised size and type
+    ///
+    /// while sizes and types are arbitrary the library is optimised for
+    /// dimensions up to ~4, and value types of float. though others _should_
+    /// work depending on what operations you pick and behaviours you expect
+    /// (eg, an int will round a little differently to floats...)
     template <
         std::size_t Rows,
         std::size_t Cols,