diff --git a/Slides/math_helper.py b/Slides/math_helper.py
index c96ff9c..e0131ec 100644
--- a/Slides/math_helper.py
+++ b/Slides/math_helper.py
@@ -1,116 +1,132 @@
 #!/usr/bin/env pyton
 ################################################################
 import numpy as np
 import presentation_helper as ph
 from sympy import latex
 from IPython.display import display, Math
 ################################################################
 
 
 def print_latex(sstr, *argv):
     args = []
     # print argv
     for a in argv:
         try:
             ff = a._repr_latex_()
             ff = ff[2:-2]
         except Exception:
             # print(e)
             ff = latex(a)
         args.append(ff)
     sstr = sstr.format(*args)
     # print (sstr)
     display(Math(latex(sstr)))
 
 ################################################################
 
 
 class ColoredMatrix:
 
     color_def = {
         'b': 'blue',
         'g': 'green',
         'r': 'red',
         'p': 'purple'
     }
 
     def __init__(self, mat):
 
         if isinstance(mat, ColoredMatrix):
             self.mat = mat.mat
         else:
             self.mat = mat
-        self.colors = np.zeros(self.mat.shape, dtype=str)
+        self.colors = np.zeros(self.mat.shape, dtype='S10')
+        self.alternative = np.zeros(self.mat.shape, dtype='S10')
         self.sym = False
 
     def __len__(self):
         return self.mat.__len__()
 
     def dot(self, mat):
         return self.mat.dot(mat)
 
+    def __mul__(self, n):
+        return self.mat.__mul__(n)
+
+    def __rmul__(self, n):
+        return n*self.mat
+
     def evalf(self, *args):
         mat_eval = self.mat.evalf(*args)
         new_mat = ColoredMatrix(mat_eval)
         new_mat.colors = self.colors.copy()
         return new_mat
 
     def __getitem__(self, index):
         return self.mat.__getitem__(index)
 
     def __setitem__(self, index, value):
         return self.mat.__setitem__(index, value)
 
+    def _get_coeff(self, i, j=0):
+        if self.alternative[i, j] != '':
+            return self.alternative[i, j]
+        else:
+            return latex(self.mat[i, j])
+
     def _colored_coeff(self, i, j=0):
 
         if self.sym is True:
             if i == self.mat.shape[0]-1 and j == 0:
                 return 'Sym.'
             elif i > j:
                 return ''
         if self.colors[i, j] in self.color_def:
             color = self.color_def[self.colors[i, j]]
         else:
             color = 'black'
-        return (r'{\color{' + color + '}{' +
-                latex(self.mat[i, j])
-                + '}}')
+
+        coeff = self._get_coeff(i, j)
+        if coeff == '':
+            return ''
+
+        return (r'{\color{' + color + '}{' + coeff + '}}')
 
     def _repr_latex_(self):
         m = self.mat.shape[0]
 
         if len(self.mat.shape) > 1 and self.mat.shape[1] > 1:
             n = self.mat.shape[1]
 
             result = ''
             for i in range(0, m):
                 row = []
                 for j in range(0, n):
                     row.append(self._colored_coeff(i, j))
 
                 result += ' & '.join(row)
                 if i < m-1:
                     result += r'\\'
             result = (r'\left[\begin{array}{' + 'c'*n + '}' +
                       result + r'\end{array}\right]')
 
         else:
             rows = []
             for i in range(0, m):
                 rows.append(self._colored_coeff(i))
             result = r'\\'.join(rows)
             result = (r'\left\{\begin{matrix}' +
                       result + r'\end{matrix}\right\}')
 
         return '$$' + result + '$$'
 
 ################################################################
 
 
 def init_printing():
     ph.registerFormatter(ColoredMatrix, 'image/png', ph._print_latex_png)
 
 ################################################################
 
 
 init_printing()
diff --git a/Slides/templates/reveal.tpl b/Slides/templates/reveal.tpl
index 41ecb11..9ac517a 100644
--- a/Slides/templates/reveal.tpl
+++ b/Slides/templates/reveal.tpl
@@ -1,100 +1,100 @@
 {% from 'mathjax.tpl' import mathjax %}
 
 {%- macro init_reveal(reveal_prefix) -%}
   <!-- Load and configure reveal -->
   <script src="js-markdown-extra.js"></script>
   <script src="https://cdnjs.cloudflare.com/ajax/libs/require.js/2.1.10/require.min.js"></script>
   <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script>
 
   <!-- General and theme style sheets -->
   <link rel="stylesheet" href="{{reveal_prefix}}/css/reveal.css">
   <link rel="stylesheet" href="{{reveal_prefix}}/css/theme/sky.css" id="theme">
 
   <!-- Loading the mathjax macro -->
   {{ mathjax() }}
   
   <!-- Get Font-awesome from cdn -->
   <link rel="stylesheet" href="//netdna.bootstrapcdn.com/font-awesome/4.1.0/css/font-awesome.css">
 
      
   <!-- End of reveal parts -->
 {%- endmacro %}
 
 
 
 {%- macro load_reveal(reveal_prefix) -%}
 
   <script>
     
     require(
     {
     // it makes sense to wait a little bit when you are loading
     // reveal from a cdn in a slow connection environment
     waitSeconds: 1
     },
     [
     "{{reveal_prefix}}/lib/js/head.min.js",
     "{{reveal_prefix}}/js/reveal.js"
     ],
     
     function(head, Reveal){
         
       Reveal.initialize({
       //width: '1200px',
       //height: '100%'
       //  margins: 0.1,
       controls: true,
       progress: true,
       history: true,
       transition: 'fade',
       margin: 0.02,
       progress: true,
-      //slideNumber: true,
+      slideNumber: true,
       // Optional libraries used to extend on reveal.js plugins
       dependencies: [
       { src: '{{reveal_prefix}}/lib/js/classList.js',
         condition: function() { return !document.body.classList; }
       },
       { src: '{{reveal_prefix}}/plugin/markdown/marked.js',
         condition: function() { return !!document.querySelector( '[data-markdown]' ); }
       },
       { src: '{{reveal_prefix}}/plugin/markdown/markdown.js',
         condition: function() { return !!document.querySelector( '[data-markdown]' ); } },
       { src: '{{reveal_prefix}}/plugin/highlight/highlight.js',
         async: true, callback: function() { hljs.initHighlightingOnLoad(); }
       },
       { src: '{{reveal_prefix}}/plugin/zoom-js/zoom.js', async: true },
       { src: '{{reveal_prefix}}/plugin/notes/notes.js',
         async: true, condition: function() { return !!document.body.classList; }
       }]});
     
       var update = function(event){
         if(MathJax.Hub.getAllJax(Reveal.getCurrentSlide())){
           MathJax.Hub.Rerender(Reveal.getCurrentSlide());
         }
       };
     
       Reveal.addEventListener('slidechanged', update);
     }
     );
     
     $(document).ready(function(){
     
     //$(".cell").css("width","90%");
     //$(".cell").css("margin","0 auto");
     //$(".output_area").css("text-align","center");
     //$(".output_png").css("margin","0 auto");
     //$("img").css("margin","0 auto");
     //$(".output_html").css("margin", "0 auto");
     //$(".output_latex").css("margin", "0 auto");
     //$(".output_subarea").css("flex", "None");
     
     $( "markdown" ).each(function( index ) {
     $( this ).html(Markdown($( this ).text()));
     });
     })
   </script>
 
 
 
 {%- endmacro %}