diff --git a/src/matrix.rs b/src/matrix.rs
index f6c1302..8d4b670 100644
--- a/src/matrix.rs
+++ b/src/matrix.rs
@@ -11,14 +11,15 @@ macro_rules! int {
 
 #[derive(Debug, PartialEq)]
 pub struct Matrix {
-    pub n: usize,
+    pub n: usize, //rows
+    pub m: usize, // columns
     values: Vec<Element>,
 }
 
 impl Matrix {
-    pub fn new(n: usize, values: Vec<Element>) -> Option<Self> {
-        if n.pow(2) == values.len() {
-            Some(Matrix { n, values })
+    pub fn new(n: usize, m: usize, values: Vec<Element>) -> Option<Self> {
+        if n*m == values.len() {
+            Some(Matrix { n, m, values })
         } else {
             None
         }
@@ -40,19 +41,25 @@ impl Matrix {
             values.extend(row);
         }
 
-        Matrix::new(n, values)
+        Matrix::new(n, n, values)
     }
 }
 
 impl Index<(usize, usize)> for Matrix {
     type Output = Element;
     fn index(&self, index: (usize, usize)) -> &Self::Output {
+        if index.0>=self.m || index.1 >= self.n {
+            panic!();
+        }
         &self.values[(self.n * index.0) + index.1]
     }
 }
 
 impl IndexMut<(usize, usize)> for Matrix {
     fn index_mut(&mut self, index: (usize, usize)) -> &mut Self::Output {
+        if index.0>=self.m || index.1 >= self.n {
+            panic!();
+        }
         &mut self.values[(self.n * index.0) + index.1]
     }
 }
@@ -65,22 +72,27 @@ mod tests {
         assert_eq!(
             Matrix {
                 n: 2,
+                m: 2,
                 values: vec![int!(1), int!(2), int!(3), int!(4)],
             },
-            Matrix::new(2, vec![int!(1), int!(2), int!(3), int!(4)]).unwrap()
+            Matrix::new(2, 2, vec![int!(1), int!(2), int!(3), int!(4)]).unwrap()
         );
-        assert!(Matrix::new(3, vec![int!(1), int!(2)]).is_none());
+        assert!(Matrix::new(2, 2, vec![int!(1), int!(2)]).is_none());
     }
 
     #[test]
     fn indexes() {
-        let mut m = Matrix::new(2, vec![int!(1), int!(2), int!(3), int!(4)]).unwrap();
+        let mut m = Matrix::new(2, 2, vec![int!(1), int!(2), int!(3), int!(4)]).unwrap();
 
         assert_eq!(m[(0, 0)], int!(1));
         assert_eq!(m[(1, 0)], int!(3));
 
         m[(1, 0)] = int!(5);
         assert_eq!(m[(1, 0)], int!(5));
+
+        let m2 = Matrix::new(3, 2, vec![int!(1), int!(2), int!(3), int!(4), int!(5), int!(6)]).unwrap();
+        assert_eq!(m2[(0, 2)], int!(3));
+        assert_eq!(m2[(1, 0)], int!(4));
     }
 
     #[test]