diff --git a/include/EventManager.hpp b/include/EventManager.hpp
index 869282e..d68fdf6 100644
--- a/include/EventManager.hpp
+++ b/include/EventManager.hpp
@@ -32,6 +32,16 @@ class EventManager
         void CallbackHome();
         void CallbackHelp();
         void CallbackSort();
+        void CallbackUnits();
+
+        /// Computes the visibility of the selected line and scrolls the element list if needed.
+        void ScrollList();
+
+        /// Sorts the elements of the current node according to the sorting method currently selected.
+        void SortNodeElements();
+
+        /// Updates the screen based on the current state.
+        void UpdateScreen();
 
         void DebugPrintState();
     
@@ -43,6 +53,7 @@ class EventManager
         int currentLine;                //<! Currently selected line
         TreeNodeDiskUsage *currentNode; //<! Pointer to the currently displayed node.
         int sortType;                   //<! Entry sort type : 0 -> size descending, 1 -> name ascending
+        bool SI_units;                  //<! Indicates whether SI units should be used.
 };
 
 #endif
diff --git a/src/Display.cpp b/src/Display.cpp
index db551af..6444d10 100644
--- a/src/Display.cpp
+++ b/src/Display.cpp
@@ -57,15 +57,18 @@ void Display::UpdateScreenSize()
 
 void Display::HighlightLine(unsigned int i, bool highlight)
 {
-    if(highlight)
+    if(i < lines.size())
     {
-        if(lines[i].substr(0, 4) != C_INVERT_FG_BG)
-            lines[i] = C_INVERT_FG_BG + lines[i] + C_RESET;
-    }
-    else
-    {
-        if(lines[i].substr(0, 4) == C_INVERT_FG_BG)
-            lines[i] = lines[i].substr(4, lines[i].size()-4-4);
+        if(highlight)
+        {
+            if(lines[i].substr(0, 4) != C_INVERT_FG_BG)
+                lines[i] = C_INVERT_FG_BG + lines[i] + C_RESET;
+        }
+        else
+        {
+            if(lines[i].substr(0, 4) == C_INVERT_FG_BG)
+                lines[i] = lines[i].substr(4, lines[i].size()-4-4);
+        }
     }
 }
 
@@ -100,6 +103,9 @@ void Display::DisplayTreeNode(TreeNodeDiskUsage const& treeNode, size_t topLine,
         lines[i+2] = LeftJustify(lineStream.str(), screenCols);
     }
 
+    if(!treeNode.GetChildrenCount())
+        lines[2] = LeftJustify("   [Empty directory]", screenCols);
+
     // Write footer
     std::stringstream footerSstream; footerSstream << "Total disk usage:   " << Bytes2HumanReadable(treeNode.GetTotalSizeOnDisk(), SI_units)
                                                    << "   Apparent size:   " << Bytes2HumanReadable(treeNode.GetTotalSize(), SI_units)
diff --git a/src/EventManager.cpp b/src/EventManager.cpp
index 94c336d..c1d6e5c 100644
--- a/src/EventManager.cpp
+++ b/src/EventManager.cpp
@@ -15,8 +15,12 @@ EventManager::EventManager(Display & display_, TreeNodeDiskUsage & rootNode_)
    topLine(0),
    currentLine(0),
    currentNode(&rootNode),
-   sortType(0)
-{}
+   sortType(0),
+   SI_units(true)
+{
+    SortNodeElements();
+    UpdateScreen();
+}
 
 EventManager::~EventManager() {}
 
@@ -70,6 +74,8 @@ void EventManager::MainEventLoop()
                     CallbackHelp();
                 else if(c == 's' || c == 'S')
                     CallbackSort();
+                else if(c == 'u' || c == 'U')
+                    CallbackUnits();
             }
             else
             {
@@ -103,53 +109,50 @@ void EventManager::MainEventLoop()
 
 void EventManager::CallbackArrowUp()
 {
-    std::cout << "CallbackArrowUp\n";// DEBUG
     if(currentNode == NULL) return;
     if(currentNode->GetChildrenCount())
-        currentLine = (currentLine - 1) % currentNode->GetChildrenCount();
-    DebugPrintState();
+        currentLine = ((currentLine - 1) < 0) ? (currentNode->GetChildrenCount() - 1) : ((currentLine - 1) % currentNode->GetChildrenCount());
+    ScrollList();
+    UpdateScreen();
 }
 
 void EventManager::CallbackArrowDown()
 {
-    std::cout << "CallbackArrowDown\n";// DEBUG
     if(currentNode == NULL) return;
     if(currentNode->GetChildrenCount())
         currentLine = (currentLine + 1) % currentNode->GetChildrenCount();
-    DebugPrintState();
+    ScrollList();
+    UpdateScreen();
 }
 
 void EventManager::CallbackArrowLeft()
 {
-    std::cout << "CallbackArrowLeft\n";// DEBUG
     if(currentNode == NULL) return;
     CallbackBackspace();
 }
 
 void EventManager::CallbackArrowRight()
 {
-    std::cout << "CallbackArrowRight\n";// DEBUG
     if(currentNode == NULL) return;
     CallbackEnter();
 }
 
 void EventManager::CallbackEnter()
 {
-    std::cout << "CallbackEnter\n";// DEBUG
     if(currentNode == NULL) return;
     if((size_t)currentLine < currentNode->GetChildrenCount())
         if(currentNode->GetChild(currentLine).IsFolder())
         {
             currentNode = &currentNode->GetChild(currentLine);
+            SortNodeElements();
             topLine = 0;
             currentLine = 0;
         }
-    DebugPrintState();
+    UpdateScreen();
 }
 
 void EventManager::CallbackBackspace()
 {
-    std::cout << "CallbackBackspace\n";// DEBUG
     if(currentNode == NULL) return;
     // Go up one level
     if(currentNode->GetParent() != NULL)
@@ -158,38 +161,70 @@ void EventManager::CallbackBackspace()
         topLine = 0;
         currentLine = 0;
     }
-    DebugPrintState();
+    UpdateScreen();
 }
 
 void EventManager::CallbackHome()
 {
-    std::cout << "CallbackHome\n";// DEBUG
     if(currentNode == NULL) return;
     // Set the current node to be the root node (go back "home").
     currentNode = &rootNode;
     topLine = 0;
     currentLine = 0;
-    DebugPrintState();
+    UpdateScreen();
 }
 
 void EventManager::CallbackHelp()
 {
-    std::cout << "CallbackHelp\n";// DEBUG
     if(currentNode == NULL) return;
-
-    DebugPrintState();
+    
+    UpdateScreen();
 }
 
 void EventManager::CallbackSort()
 {
-    std::cout << "CallbackSort\n";// DEBUG
     if(currentNode == NULL) return;
     sortType = (sortType + 1) % 2;// Cycle through all the sort types.
+    SortNodeElements();
+    UpdateScreen();
+}
+
+void EventManager::CallbackUnits()
+{
+    if(currentNode == NULL) return;
+    SI_units ^= true;// Invert the SI_units flag.
+    UpdateScreen();
+}
+
+void EventManager::ScrollList()
+{
+    /*if(currentNode == NULL) return;
+    if(currentNode->GetChildrenCount())
+    {
+        // compute visibility of selected line and scroll if needed
+        PRINT_VAR(2 + currentLine - topLine);
+        PRINT_VAR(display.Rows()-1);
+        if((2 + currentLine - topLine) >= (display.Rows()-1))
+            topLine = currentLine - (display.Rows() - 2);// DOES NOT WORK. WORK IN PROGRESS.
+    }//*/
+}
+
+void EventManager::SortNodeElements()
+{
+    if(currentNode == NULL) return;
     if(sortType == 0)
         currentNode->SortBySizeDesc();
     else if(sortType == 1)
         currentNode->SortByNameAsc();
-    DebugPrintState();
+}
+
+void EventManager::UpdateScreen()
+{
+    //DebugPrintState(); return;// DEBUG
+    Display::ClearScreen();
+    display.DisplayTreeNode(*currentNode, topLine, SI_units);
+    display.HighlightLine(2 + topLine + currentLine, true);
+    display.DrawScreenLines();
 }
 
 void EventManager::DebugPrintState()
diff --git a/src/main.cpp b/src/main.cpp
index 51a84f5..019911d 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -8,7 +8,7 @@ using std::cout;
 using std::cerr;
 using std::endl;
 
-#define D_UNIT_TESTS
+//#define D_UNIT_TESTS
 
 #include <test.hpp>
 
@@ -82,7 +82,12 @@ int main(int argc, char *argv[])
 		tree.PrintTree(maxDepth, true);
 	
 	// Interactive mode : the user can navigate through the tree structure.
-	// else
+	else
+	{
+		tree.BuildParentLinks();
+		EventManager eventManager(display, tree);
+		eventManager.MainEventLoop();
+	}
 
 	return 0;
 }
diff --git a/src/test.cpp b/src/test.cpp
index 5feef46..fc99363 100644
--- a/src/test.cpp
+++ b/src/test.cpp
@@ -203,7 +203,7 @@ void runTests(int argc, char *argv[])
 		Display display;
 		TreeNodeDiskUsage tree(rootpath);
 		tree.BuildTree(false);
-		tree.SortBySizeDesc();
+		tree.SortBySizeDesc(true);
 		display.DisplayTreeNode(tree, 0, true);
 		//Display::ClearScreen();
 		display.DrawScreenLines();