diff --git a/doc/011.png b/doc/011.png
new file mode 100644
index 0000000..c864d2c
Binary files /dev/null and b/doc/011.png differ
diff --git a/doc/012.gif b/doc/012.gif
new file mode 100644
index 0000000..88a0dfe
Binary files /dev/null and b/doc/012.gif differ
diff --git a/doc/012.mkv b/doc/012.mkv
new file mode 100644
index 0000000..2a297ed
Binary files /dev/null and b/doc/012.mkv differ
diff --git a/framebuffer.cpp b/framebuffer.cpp
new file mode 100644
index 0000000..860679d
--- /dev/null
+++ b/framebuffer.cpp
@@ -0,0 +1,30 @@
+#include <iostream>
+#include <vector>
+#include <cstdint>
+#include <cassert>
+
+#include "framebuffer.h"
+#include "utils.h"
+
+void FrameBuffer::set_pixel(const size_t x, const size_t y, const uint32_t color) {
+    assert(img.size()==w*h && x<w && y<h);
+    img[x+y*w] = color;
+}
+
+void FrameBuffer::draw_rectangle(const size_t rect_x, const size_t rect_y, const size_t rect_w, const size_t rect_h, const uint32_t color) {
+    assert(img.size()==w*h);
+    for (size_t i=0; i<rect_w; i++) {
+        for (size_t j=0; j<rect_h; j++) {
+            size_t cx = rect_x+i;
+            size_t cy = rect_y+j;
+            if (cx<w && cy<h) // no need to check for negative values (unsigned variables)
+                set_pixel(cx, cy, color);
+        }
+    }
+}
+
+void FrameBuffer::clear(const uint32_t color) {
+    img = std::vector<uint32_t>(w*h, color);
+}
+
+
diff --git a/framebuffer.h b/framebuffer.h
new file mode 100644
index 0000000..6acf5fc
--- /dev/null
+++ b/framebuffer.h
@@ -0,0 +1,17 @@
+#ifndef FRAMEBUFFER_H
+#define FRAMEBUFFER_H
+
+#include <cstdlib>
+#include <vector>
+
+struct FrameBuffer {
+    size_t w, h; // image dimensions
+    std::vector<uint32_t> img; // storage container
+
+    void clear(const uint32_t color);
+    void set_pixel(const size_t x, const size_t y, const uint32_t color);
+    void draw_rectangle(const size_t x, const size_t y, const size_t w, const size_t h, const uint32_t color);
+};
+
+#endif // FRAMEBUFFER_H
+
diff --git a/map.cpp b/map.cpp
new file mode 100644
index 0000000..4d71a98
--- /dev/null
+++ b/map.cpp
@@ -0,0 +1,36 @@
+#include <cstdlib>
+#include <cassert>
+
+#include "map.h"
+
+static const char map[] = "0000222222220000"\
+                          "1              0"\
+                          "1      11111   0"\
+                          "1     0        0"\
+                          "0     0  1110000"\
+                          "0     3        0"\
+                          "0   10000      0"\
+                          "0   3   11100  0"\
+                          "5   4   0      0"\
+                          "5   4   1  00000"\
+                          "0       1      0"\
+                          "2       1      0"\
+                          "0       0      0"\
+                          "0 0000000      0"\
+                          "0              0"\
+                          "0002222222200000";
+
+Map::Map() : w(16), h(16) {
+    assert(sizeof(map) == w*h+1); // +1 for the null terminated string
+}
+
+int Map::get(const size_t i, const size_t j) {
+    assert(i<w && j<h && sizeof(map) == w*h+1);
+    return map[i+j*w] - '0';
+}
+
+bool Map::is_empty(const size_t i, const size_t j) {
+    assert(i<w && j<h && sizeof(map) == w*h+1);
+    return map[i+j*w] == ' ';
+}
+
diff --git a/map.h b/map.h
new file mode 100644
index 0000000..adcf65e
--- /dev/null
+++ b/map.h
@@ -0,0 +1,14 @@
+#ifndef MAP_H
+#define MAP_H
+
+#include <cstdlib>
+
+struct Map {
+    size_t w, h; // overall map dimensions
+    Map();
+    int get(const size_t i, const size_t j);
+    bool is_empty(const size_t i, const size_t j);
+};
+
+#endif // MAP_H
+
diff --git a/player.h b/player.h
new file mode 100644
index 0000000..cdf8870
--- /dev/null
+++ b/player.h
@@ -0,0 +1,11 @@
+#ifndef PLAYER_H
+#define PLAYER_H
+
+struct Player {
+    float x, y; // position
+    float a;    // view direction
+    float fov;  // field of view
+};
+
+#endif // PLAYER_H
+
diff --git a/textures.cpp b/textures.cpp
new file mode 100644
index 0000000..37504c8
--- /dev/null
+++ b/textures.cpp
@@ -0,0 +1,61 @@
+#include <iostream>
+#include <vector>
+#include <cstdint>
+#include <cassert>
+#define STB_IMAGE_IMPLEMENTATION
+#include "stb_image.h"
+
+#include "utils.h"
+#include "textures.h"
+
+Texture::Texture(const std::string filename) : img_w(0), img_h(0), count(0), size(0), img() {
+    int nchannels = -1, w, h;
+    unsigned char *pixmap = stbi_load(filename.c_str(), &w, &h, &nchannels, 0);
+    if (!pixmap) {
+        std::cerr << "Error: can not load the textures" << std::endl;
+        return;
+    }
+
+    if (4!=nchannels) {
+        std::cerr << "Error: the texture must be a 32 bit image" << std::endl;
+        stbi_image_free(pixmap);
+        return;
+    }
+
+    if (w!=h*int(w/h)) {
+        std::cerr << "Error: the texture file must contain N square textures packed horizontally" << std::endl;
+        stbi_image_free(pixmap);
+        return;
+    }
+    count = w/h;
+    size = w/count;
+    img_w = w;
+    img_h = h;
+
+    img = std::vector<uint32_t>(w*h);
+    for (int j=0; j<h; j++) {
+        for (int i=0; i<w; i++) {
+            uint8_t r = pixmap[(i+j*w)*4+0];
+            uint8_t g = pixmap[(i+j*w)*4+1];
+            uint8_t b = pixmap[(i+j*w)*4+2];
+            uint8_t a = pixmap[(i+j*w)*4+3];
+            img[i+j*w] = pack_color(r, g, b, a);
+        }
+    }
+    stbi_image_free(pixmap);
+}
+
+uint32_t &Texture::get(const size_t i, const size_t j, const size_t idx) {
+    assert(i<size && j<size && idx<count);
+    return img[i+idx*size+j*img_w];
+}
+
+std::vector<uint32_t> Texture::get_scaled_column(const size_t texture_id, const size_t tex_coord, const size_t column_height) {
+    assert(tex_coord<size && texture_id<count);
+    std::vector<uint32_t> column(column_height);
+    for (size_t y=0; y<column_height; y++) {
+        column[y] = get(tex_coord, (y*size)/column_height, texture_id);
+    }
+    return column;
+}
+
diff --git a/textures.h b/textures.h
new file mode 100644
index 0000000..a833bcb
--- /dev/null
+++ b/textures.h
@@ -0,0 +1,15 @@
+#ifndef TEXTURES_H
+#define TEXTURES_H
+
+struct Texture {
+    size_t img_w, img_h; // overall image dimensions
+    size_t count, size;  // number of textures and size in pixels
+    std::vector<uint32_t> img; // textures storage container
+
+    Texture(const std::string filename);
+    uint32_t &get(const size_t i, const size_t j, const size_t idx); // get the pixel (i,j) from the textrue idx
+    std::vector<uint32_t> get_scaled_column(const size_t texture_id, const size_t tex_coord, const size_t column_height); // retrieve one column (tex_coord) from the texture texture_id and scale it to the destination size
+};
+
+#endif // TEXTURES_H
+
diff --git a/tinyraycaster.cpp b/tinyraycaster.cpp
index 8ed98a2..d5ff79f 100644
--- a/tinyraycaster.cpp
+++ b/tinyraycaster.cpp
@@ -1,185 +1,91 @@
 #define _USE_MATH_DEFINES
 #include <cmath>
 #include <iostream>
-#include <fstream>
 #include <vector>
 #include <cstdint>
 #include <cassert>
-#define STB_IMAGE_IMPLEMENTATION
-#include "stb_image.h"
+#include <sstream>
+#include <iomanip>
 
-uint32_t pack_color(const uint8_t r, const uint8_t g, const uint8_t b, const uint8_t a=255) {
-    return (a<<24) + (b<<16) + (g<<8) + r;
+#include "map.h"
+#include "utils.h"
+#include "player.h"
+#include "framebuffer.h"
+#include "textures.h"
+
+int wall_x_texcoord(const float x, const float y, Texture &tex_walls) {
+    float hitx = x - floor(x+.5); // hitx and hity contain (signed) fractional parts of x and y,
+    float hity = y - floor(y+.5); // they vary between -0.5 and +0.5, and one of them is supposed to be very close to 0
+    int tex = hitx*tex_walls.size;
+    if (std::abs(hity)>std::abs(hitx)) // we need to determine whether we hit a "vertical" or a "horizontal" wall (w.r.t the map)
+        tex = hity*tex_walls.size;
+    if (tex<0) // do not forget x_texcoord can be negative, fix that
+        tex += tex_walls.size;
+    assert(tex>=0 && tex<(int)tex_walls.size);
+    return tex;
 }
 
-void unpack_color(const uint32_t &color, uint8_t &r, uint8_t &g, uint8_t &b, uint8_t &a) {
-    r = (color >>  0) & 255;
-    g = (color >>  8) & 255;
-    b = (color >> 16) & 255;
-    a = (color >> 24) & 255;
-}
+void render(FrameBuffer &fb, Map &map, Player &player, Texture &tex_walls) {
+    fb.clear(pack_color(255, 255, 255)); // clear the screen
 
-void drop_ppm_image(const std::string filename, const std::vector<uint32_t> &image, const size_t w, const size_t h) {
-    assert(image.size() == w*h);
-    std::ofstream ofs(filename);
-    ofs << "P6\n" << w << " " << h << "\n255\n";
-    for (size_t i = 0; i < h*w; ++i) {
-        uint8_t r, g, b, a;
-        unpack_color(image[i], r, g, b, a);
-        ofs << static_cast<char>(r) << static_cast<char>(g) << static_cast<char>(b);
-    }
-    ofs.close();
-}
-
-void draw_rectangle(std::vector<uint32_t> &img, const size_t img_w, const size_t img_h, const size_t x, const size_t y, const size_t w, const size_t h, const uint32_t color) {
-    assert(img.size()==img_w*img_h);
-    for (size_t i=0; i<w; i++) {
-        for (size_t j=0; j<h; j++) {
-            size_t cx = x+i;
-            size_t cy = y+j;
-            if (cx>=img_w || cy>=img_h) continue; // no need to check for negative values (unsigned variables)
-            img[cx + cy*img_w] = color;
+    const size_t rect_w = fb.w/(map.w*2); // size of one map cell on the screen
+    const size_t rect_h = fb.h/map.h;
+    for (size_t j=0; j<map.h; j++) {  // draw the map
+        for (size_t i=0; i<map.w; i++) {
+            if (map.is_empty(i, j)) continue; // skip empty spaces
+            size_t rect_x = i*rect_w;
+            size_t rect_y = j*rect_h;
+            size_t texid = map.get(i, j);
+            assert(texid<tex_walls.count);
+            fb.draw_rectangle(rect_x, rect_y, rect_w, rect_h, tex_walls.get(0, 0, texid)); // the color is taken from the upper left pixel of the texture #texid
         }
     }
-}
 
-bool load_texture(const std::string filename, std::vector<uint32_t> &texture, size_t &text_size, size_t &text_cnt) {
-    int nchannels = -1, w, h;
-    unsigned char *pixmap = stbi_load(filename.c_str(), &w, &h, &nchannels, 0);
-    if (!pixmap) {
-        std::cerr << "Error: can not load the textures" << std::endl;
-        return false;
-    }
+    for (size_t i=0; i<fb.w/2; i++) { // draw the visibility cone AND the "3D" view
+        float angle = player.a-player.fov/2 + player.fov*i/float(fb.w/2);
+        for (float t=0; t<20; t+=.01) { // ray marching loop
+            float x = player.x + t*cos(angle);
+            float y = player.y + t*sin(angle);
+            fb.set_pixel(x*rect_w, y*rect_h, pack_color(160, 160, 160)); // this draws the visibility cone
 
-    if (4!=nchannels) {
-        std::cerr << "Error: the texture must be a 32 bit image" << std::endl;
-        stbi_image_free(pixmap);
-        return false;
-    }
+            if (map.is_empty(x, y)) continue;
 
-    text_cnt = w/h;
-    text_size = w/text_cnt;
-    if (w!=h*int(text_cnt)) {
-        std::cerr << "Error: the texture file must contain N square textures packed horizontally" << std::endl;
-        stbi_image_free(pixmap);
-        return false;
-    }
-
-    texture = std::vector<uint32_t>(w*h);
-    for (int j=0; j<h; j++) {
-        for (int i=0; i<w; i++) {
-            uint8_t r = pixmap[(i+j*w)*4+0];
-            uint8_t g = pixmap[(i+j*w)*4+1];
-            uint8_t b = pixmap[(i+j*w)*4+2];
-            uint8_t a = pixmap[(i+j*w)*4+3];
-            texture[i+j*w] = pack_color(r, g, b, a);
-        }
-    }
-    stbi_image_free(pixmap);
-    return true;
-}
-
-std::vector<uint32_t> texture_column(const std::vector<uint32_t> &img, const size_t texsize, const size_t ntextures, const size_t texid, const size_t texcoord, const size_t column_height) {
-    const size_t img_w = texsize*ntextures;
-    const size_t img_h = texsize;
-    assert(img.size()==img_w*img_h && texcoord<texsize && texid<ntextures);
-    std::vector<uint32_t> column(column_height);
-    for (size_t y=0; y<column_height; y++) {
-        size_t pix_x = texid*texsize + texcoord;
-        size_t pix_y = (y*texsize)/column_height;
-        column[y] = img[pix_x + pix_y*img_w];
-    }
-    return column;
+            size_t texid = map.get(x, y); // our ray touches a wall, so draw the vertical column to create an illusion of 3D
+            assert(texid<tex_walls.count);
+            size_t column_height = fb.h/(t*cos(angle-player.a));
+            int x_texcoord = wall_x_texcoord(x, y, tex_walls);
+            std::vector<uint32_t> column = tex_walls.get_scaled_column(texid, x_texcoord, column_height);
+            int pix_x = i + fb.w/2; // we are drawing at the right half of the screen, thus +fb.w/2
+            for (size_t j=0; j<column_height; j++) { // copy the texture column to the framebuffer
+                int pix_y = j + fb.h/2 - column_height/2;
+                if (pix_y>=0 && pix_y<(int)fb.h) {
+                    fb.set_pixel(pix_x, pix_y, column[j]);
+                }
+            }
+            break;
+        } // ray marching loop
+    } // field of view ray sweeping
 }
 
 int main() {
-    const size_t win_w = 1024; // image width
-    const size_t win_h = 512;  // image height
-    std::vector<uint32_t> framebuffer(win_w*win_h, pack_color(255, 255, 255)); // the image itself, initialized to white
-
-    const size_t map_w = 16; // map width
-    const size_t map_h = 16; // map height
-    const char map[] = "0000222222220000"\
-                       "1              0"\
-                       "1      11111   0"\
-                       "1     0        0"\
-                       "0     0  1110000"\
-                       "0     3        0"\
-                       "0   10000      0"\
-                       "0   3   11100  0"\
-                       "5   4   0      0"\
-                       "5   4   1  00000"\
-                       "0       1      0"\
-                       "2       1      0"\
-                       "0       0      0"\
-                       "0 0000000      0"\
-                       "0              0"\
-                       "0002222222200000"; // our game map
-    assert(sizeof(map) == map_w*map_h+1); // +1 for the null terminated string
-    float player_x = 3.456; // player x position
-    float player_y = 2.345; // player y position
-    float player_a = 1.523; // player view direction
-    const float fov = M_PI/3.; // field of view
-
-    std::vector<uint32_t> walltext; // textures for the walls
-    size_t walltext_size;  // texture dimensions (it is a square)
-    size_t walltext_cnt;   // number of different textures in the image
-    if (!load_texture("../walltext.png", walltext, walltext_size, walltext_cnt)) {
+    FrameBuffer fb{1024, 512, std::vector<uint32_t>(1024*512, pack_color(255, 255, 255))};
+    Player player{3.456, 2.345, 1.523, M_PI/3.};
+    Map map;
+    Texture tex_walls("../walltext.png");
+    if (!tex_walls.count) {
         std::cerr << "Failed to load wall textures" << std::endl;
         return -1;
     }
 
-    const size_t rect_w = win_w/(map_w*2);
-    const size_t rect_h = win_h/map_h;
-    for (size_t j=0; j<map_h; j++) { // draw the map
-        for (size_t i=0; i<map_w; i++) {
-            if (map[i+j*map_w]==' ') continue; // skip empty spaces
-            size_t rect_x = i*rect_w;
-            size_t rect_y = j*rect_h;
-            size_t texid = map[i+j*map_w] - '0';
-            assert(texid<walltext_cnt);
-            draw_rectangle(framebuffer, win_w, win_h, rect_x, rect_y, rect_w, rect_h, walltext[texid*walltext_size]); // the color is taken from the upper left pixel of the texture #texid
-        }
+    for (size_t frame=0; frame<360; frame++) {
+        std::stringstream ss;
+        ss << std::setfill('0') << std::setw(5) << frame << ".ppm";
+        player.a += 2*M_PI/360;
+
+        render(fb, map, player, tex_walls);
+        drop_ppm_image(ss.str(), fb.img, fb.w, fb.h);
     }
 
-    for (size_t i=0; i<win_w/2; i++) { // draw the visibility cone AND the "3D" view
-        float angle = player_a-fov/2 + fov*i/float(win_w/2);
-        for (float t=0; t<20; t+=.01) {
-            float cx = player_x + t*cos(angle);
-            float cy = player_y + t*sin(angle);
-
-            int pix_x = cx*rect_w;
-            int pix_y = cy*rect_h;
-            framebuffer[pix_x + pix_y*win_w] = pack_color(160, 160, 160); // this draws the visibility cone
-
-            if (map[int(cx)+int(cy)*map_w]!=' ') { // our ray touches a wall, so draw the vertical column to create an illusion of 3D
-                size_t texid = map[int(cx)+int(cy)*map_w] - '0';
-                assert(texid<walltext_cnt);
-                size_t column_height = win_h/(t*cos(angle-player_a));
-
-                float hitx = cx - floor(cx+.5); // hitx and hity contain (signed) fractional parts of cx and cy,
-                float hity = cy - floor(cy+.5); // they vary between -0.5 and +0.5, and one of them is supposed to be very close to 0
-                int x_texcoord = hitx*walltext_size;
-                if (std::abs(hity)>std::abs(hitx)) { // we need to determine whether we hit a "vertical" or a "horizontal" wall (w.r.t the map)
-                    x_texcoord = hity*walltext_size;
-                }
-                if (x_texcoord<0) x_texcoord += walltext_size; // do not forget x_texcoord can be negative, fix that
-                assert(x_texcoord>=0 && x_texcoord<(int)walltext_size);
-
-                std::vector<uint32_t> column = texture_column(walltext, walltext_size, walltext_cnt, texid, x_texcoord, column_height);
-                pix_x = win_w/2+i;
-                for (size_t j=0; j<column_height; j++) {
-                    pix_y = j + win_h/2-column_height/2;
-                    if (pix_y<0 || pix_y>=(int)win_h) continue;
-                    framebuffer[pix_x + pix_y*win_w] = column[j];
-                }
-                break;
-            }
-        }
-    }
-
-    drop_ppm_image("./out.ppm", framebuffer, win_w, win_h);
-
     return 0;
 }
 
diff --git a/utils.cpp b/utils.cpp
new file mode 100644
index 0000000..2d49fb9
--- /dev/null
+++ b/utils.cpp
@@ -0,0 +1,31 @@
+#include <iostream>
+#include <fstream>
+#include <vector>
+#include <cstdint>
+#include <cassert>
+
+#include "utils.h"
+
+uint32_t pack_color(const uint8_t r, const uint8_t g, const uint8_t b, const uint8_t a) {
+    return (a<<24) + (b<<16) + (g<<8) + r;
+}
+
+void unpack_color(const uint32_t &color, uint8_t &r, uint8_t &g, uint8_t &b, uint8_t &a) {
+    r = (color >>  0) & 255;
+    g = (color >>  8) & 255;
+    b = (color >> 16) & 255;
+    a = (color >> 24) & 255;
+}
+
+void drop_ppm_image(const std::string filename, const std::vector<uint32_t> &image, const size_t w, const size_t h) {
+    assert(image.size() == w*h);
+    std::ofstream ofs(filename);
+    ofs << "P6\n" << w << " " << h << "\n255\n";
+    for (size_t i = 0; i < h*w; ++i) {
+        uint8_t r, g, b, a;
+        unpack_color(image[i], r, g, b, a);
+        ofs << static_cast<char>(r) << static_cast<char>(g) << static_cast<char>(b);
+    }
+    ofs.close();
+}
+
diff --git a/utils.h b/utils.h
new file mode 100644
index 0000000..6386189
--- /dev/null
+++ b/utils.h
@@ -0,0 +1,13 @@
+#ifndef UTILS_H
+#define UTILS_H
+
+#include <vector>
+#include <cstdint>
+#include <string>
+
+uint32_t pack_color(const uint8_t r, const uint8_t g, const uint8_t b, const uint8_t a=255);
+void unpack_color(const uint32_t &color, uint8_t &r, uint8_t &g, uint8_t &b, uint8_t &a);
+void drop_ppm_image(const std::string filename, const std::vector<uint32_t> &image, const size_t w, const size_t h);
+
+#endif // UTILS_H
+