diff --git a/src/matrix/mat.rs b/src/matrix/mat.rs
index a951c05..82acb38 100644
--- a/src/matrix/mat.rs
+++ b/src/matrix/mat.rs
@@ -16,7 +16,7 @@ impl<T: Clone> Matrix<T> {
         let cols = cols_data.len();
         assert!(cols > 0, "need at least one column");
         // Handle empty cols_data
-        let rows = cols_data.get(0).map_or(0, |c| c.len()); 
+        let rows = cols_data.get(0).map_or(0, |c| c.len());
         // Allow 0-row matrices if columns are empty, but not 0-col matrices if rows > 0
         assert!(
             rows > 0 || cols == 0,
@@ -89,9 +89,12 @@ impl<T: Clone> Matrix<T> {
         self.cols
     }
 
+    /// Get element reference (immutable). Panics on out-of-bounds.
     pub fn get(&self, r: usize, c: usize) -> &T {
         &self[(r, c)]
     }
+
+    /// Get element reference (mutable). Panics on out-of-bounds.
     pub fn get_mut(&mut self, r: usize, c: usize) -> &mut T {
         &mut self[(r, c)]
     }
@@ -107,6 +110,7 @@ impl<T: Clone> Matrix<T> {
         let start = c * self.rows;
         &self.data[start..start + self.rows]
     }
+
     #[inline]
     pub fn column_mut(&mut self, c: usize) -> &mut [T] {
         assert!(
@@ -130,7 +134,7 @@ impl<T: Clone> Matrix<T> {
         })
     }
 
-    /// Swaps two columns in the matrix.
+    /// Swaps two columns in the matrix. Panics on out-of-bounds.
     pub fn swap_columns(&mut self, c1: usize, c2: usize) {
         assert!(
             c1 < self.cols,
@@ -183,7 +187,7 @@ impl<T: Clone> Matrix<T> {
 impl<T: Clone> Matrix<T> {
     /// Adds a column to the matrix at the specified index.
     pub fn add_column(&mut self, index: usize, column: Vec<T>) {
-        assert!(index <= self.cols, "add_column index {} out of bounds for {} columns", index, self.cols);
+        assert!(index <= self.cols,"add_column index {} out of bounds for {} columns",index,self.cols);
         assert_eq!(column.len(), self.rows, "column length mismatch");
 
         for (r, value) in column.into_iter().enumerate() {
@@ -194,8 +198,8 @@ impl<T: Clone> Matrix<T> {
 
     /// Adds a row to the matrix at the specified index.
     pub fn add_row(&mut self, index: usize, row: Vec<T>) {
-        assert!(index <= self.rows, "add_row index {} out of bounds for {} rows", index, self.rows);
-        assert_eq!(row.len(), self.cols, "row length mismatch");
+        assert!(index <= self.rows,"add_row index {} out of bounds for {} rows",index,self.rows);
+        assert_eq!(row.len(),self.cols,"row length mismatch: expected {} (cols), got {}",self.cols,row.len());
 
         for (c, value) in row.into_iter().enumerate() {
             self.data.insert(c * (self.rows + 1) + index, value);
@@ -261,14 +265,16 @@ impl<'a, T> MatrixRow<'a, T> {
 /// Specifies the axis along which to perform a reduction operation.
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum Axis {
-    /// Apply reduction along columns (vertical axis).
+    /// Apply reduction along columns (vertical axis). Result has 1 row.
     Col,
-    /// Apply reduction along rows (horizontal axis).
+    /// Apply reduction along rows (horizontal axis). Result has 1 column.
     Row,
 }
 
+// --- Broadcasting ---
+
 /// A trait to turn either a `Matrix<T>` or a scalar T into a `Vec<T>` of
-/// length `rows*cols` (broadcasting the scalar).
+/// length `rows*cols` (broadcasting the scalar). Used for comparisons.
 pub trait Broadcastable<T> {
     fn to_vec(&self, rows: usize, cols: usize) -> Vec<T>;
 }