diff --git a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Camera.cpp b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Camera.cpp
index 4bb0083ee9c..0b4b6fa40f1 100644
--- a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Camera.cpp
+++ b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Camera.cpp
@@ -17,7 +17,7 @@ Camera::Camera() :
 {}
 
 //! \brief
-void Camera::perspective(float fov, float aspect, float z_near, float z_far) {
+void Camera::perspective(qreal fov, qreal aspect, qreal z_near, qreal z_far) {
   m_z_near = z_near;
   m_z_far = z_far;
 
diff --git a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Camera.h b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Camera.h
index c1f014a535b..9d166a794b0 100644
--- a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Camera.h
+++ b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Camera.h
@@ -21,9 +21,9 @@ public:
   void set_pos(float x, float y, float z) { m_pos = QVector3D(x,y,z); }
   const QVector3D& get_pos() const { return m_pos; }
 
-  void perspective(float fov, float aspect_ratio, float z_near, float z_far);
+  void perspective(qreal fov, qreal aspect_ratio, qreal z_near, qreal z_far);
 
-  float get_z_near() const { return m_z_near; }
+  qreal get_z_near() const { return m_z_near; }
   QMatrix4x4 get_view_matrix() const;
   QMatrix4x4 get_projection_matrix() const { return m_projection; }
 
@@ -50,7 +50,7 @@ private:
   QVector3D m_saved_uy;
   QVector3D m_saved_uz;
 
-  float m_z_near, m_z_far;
+  qreal m_z_near, m_z_far;
 
   QMatrix4x4 m_projection;
 };
diff --git a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Line_strips.cpp b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Line_strips.cpp
index b6a21d639e7..93ab6cd5596 100644
--- a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Line_strips.cpp
+++ b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Line_strips.cpp
@@ -20,7 +20,7 @@ Line_strips::Line_strips(std::vector<QVector3D>& line_strip_points) {
   for (const auto& p : line_strip_points)
     vertex_data.push_back(p);
 
-  const auto end_of_current_arc_points = vertex_data.size();
+  const auto end_of_current_arc_points = static_cast<GLuint>(vertex_data.size());
   m_offsets.push_back(end_of_current_arc_points);
 
   // DEFINE OPENGL BUFFERS
@@ -56,7 +56,7 @@ Line_strips::Line_strips(std::vector<std::vector<QVector3D>>& arcs) {
   for (const auto& arc : arcs) {
     for(const auto& p : arc) vertex_data.push_back(p);
 
-    const auto end_of_current_arc_points = vertex_data.size();
+    const auto end_of_current_arc_points = static_cast<GLuint>(vertex_data.size());
     m_offsets.push_back(end_of_current_arc_points);
   }
 
diff --git a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Main_widget.cpp b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Main_widget.cpp
index 675e7af1c86..0511137f4ae 100644
--- a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Main_widget.cpp
+++ b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Main_widget.cpp
@@ -146,7 +146,7 @@ void Main_widget::initializeGL() {
   init_geometry();
   init_shader_programs();
 
-  m_current_approx_error = 0.001;
+  m_current_approx_error = 0.001f;
   init_country_borders(m_current_approx_error);
 
   glClearColor(0, 0, 0, 1);
diff --git a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Main_widget.h b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Main_widget.h
index 24db2401926..c2f69c2d087 100644
--- a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Main_widget.h
+++ b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Main_widget.h
@@ -84,7 +84,7 @@ private:
   std::unique_ptr<Line_strips> m_gr_all_country_borders;
 
   // used when dimming / highlighting selected countries
-  const float m_dimming_factor = 0.4;
+  const float m_dimming_factor = 0.4f;
 
   // GUI: event handler for picking with right mouse button
   std::unique_ptr<GUI_event_handler> m_pick_handler;
diff --git a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Sphere.cpp b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Sphere.cpp
index 8d83fd5a72c..8a24ae4c6b8 100644
--- a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Sphere.cpp
+++ b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Sphere.cpp
@@ -62,12 +62,12 @@ Sphere::Sphere(std::size_t num_slices, std::size_t num_stacks, float r) {
   std::vector<GLuint> indices;
 
   // NORTH CAP
-  const std::size_t north_vertex_index = 0;
+  const GLuint north_vertex_index = 0;
   const auto north_cap_vertex_index_start = starting_index_of_middle_vertices;
-  for (std::size_t i = 0; i < num_slices; i++) {
+  for (std::size_t i = 0; i < num_slices; ++i) {
     indices.push_back(north_vertex_index);
-    indices.push_back(north_cap_vertex_index_start + i);
-    indices.push_back(north_cap_vertex_index_start + (i + 1) % num_slices);
+    indices.push_back(static_cast<GLuint>(north_cap_vertex_index_start + i));
+    indices.push_back(static_cast<GLuint>(north_cap_vertex_index_start + (i + 1) % num_slices));
   }
 
   // 0 = NORTH VERTEX
@@ -81,13 +81,13 @@ Sphere::Sphere(std::size_t num_slices, std::size_t num_stacks, float r) {
   //                                                the last stack (# numStacks)
 
   // SOUTH CAP
-  const std::size_t south_vertex_index = 1;
+  const GLuint south_vertex_index = 1;
   const std::size_t south_cap_index_start = starting_index_of_middle_vertices +
     (num_stacks - 2) * num_slices;
   for (std::size_t i = 0; i < num_slices; ++i) {
     const auto vi0 = south_vertex_index;
-    const auto vi1 = south_cap_index_start + i;
-    const auto vi2 = south_cap_index_start + (i + 1) % num_slices;
+    const auto vi1 = static_cast<GLuint>(south_cap_index_start + i);
+    const auto vi2 = static_cast<GLuint>(south_cap_index_start + (i + 1) % num_slices);
     indices.push_back(vi2);
     indices.push_back(vi1);
     indices.push_back(vi0);
@@ -104,10 +104,10 @@ Sphere::Sphere(std::size_t num_slices, std::size_t num_stacks, float r) {
       //std::size_t vi1 = nextStackStartIndex + i;
       //std::size_t vi2 = nextStackStartIndex + (i + 1) % numSlices;
       //std::size_t vi3 = stackStartIndex + (i + 1) % numSlices;
-      std::size_t vi0 = stack_start_index + i;
-      std::size_t vi1 = stack_start_index + (i + 1) % num_slices;
-      std::size_t vi2 = next_stack_start_index + i;
-      std::size_t vi3 = next_stack_start_index + (i + 1) % num_slices;
+      auto vi0 = static_cast<GLuint>(stack_start_index + i);
+      auto vi1 = static_cast<GLuint>(stack_start_index + (i + 1) % num_slices);
+      auto vi2 = static_cast<GLuint>(next_stack_start_index + i);
+      auto vi3 = static_cast<GLuint>(next_stack_start_index + (i + 1) % num_slices);
 
       indices.push_back(vi0);
       indices.push_back(vi2);
@@ -118,7 +118,7 @@ Sphere::Sphere(std::size_t num_slices, std::size_t num_stacks, float r) {
       indices.push_back(vi1);
     }
   }
-  m_num_indices = indices.size();
+  m_num_indices = static_cast<GLuint>(indices.size());
 
   // DEFINE OPENGL BUFFERS
   glGenVertexArrays(1, &m_vao);
diff --git a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Triangles.cpp b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Triangles.cpp
index d924d4299fa..39eb89a7a5b 100644
--- a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Triangles.cpp
+++ b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Triangles.cpp
@@ -35,7 +35,7 @@ Triangles::Triangles(std::vector<QVector3D>& vertices) {
   // DEFINE OPENGL BUFFERS
   glGenVertexArrays(1, &m_vao);
   glBindVertexArray(m_vao);
-  m_num_vertices = vertices.size();
+  m_num_vertices = static_cast<GLsizei>(vertices.size());
 
   // Vertex Buffer
   glGenBuffers(1, &m_vbo);
diff --git a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Triangles.h b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Triangles.h
index 0cc21b73925..ce24fc55d6a 100644
--- a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Triangles.h
+++ b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Triangles.h
@@ -30,7 +30,7 @@ public:
 private:
   GLuint m_vao;
   GLuint m_vbo;
-  std::size_t m_num_vertices;
+  GLsizei m_num_vertices;
   QVector4D m_color;
 };
 
diff --git a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Vertices.cpp b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Vertices.cpp
index fa6fd3f1bd5..dc64111bf93 100644
--- a/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Vertices.cpp
+++ b/Arrangement_on_surface_2/demo/Arrangement_on_surface_2_earth/Vertices.cpp
@@ -14,7 +14,7 @@ Vertices::Vertices(const std::vector<QVector3D>& vertices) {
   initializeOpenGLFunctions();
 
   auto& vertex_data = vertices;
-  m_num_indices = vertices.size();
+  m_num_indices = static_cast<GLsizei>(vertices.size());
 
   // DEFINE OPENGL BUFFERS
   glGenVertexArrays(1, &m_vao);