diff --git a/doc/002.png b/doc/002.png
new file mode 100644
index 0000000..1812ba8
Binary files /dev/null and b/doc/002.png differ
diff --git a/tinyraycaster.cpp b/tinyraycaster.cpp
index 4d4e6d8..6d51bcd 100644
--- a/tinyraycaster.cpp
+++ b/tinyraycaster.cpp
@@ -29,11 +29,43 @@ void drop_ppm_image(const std::string filename, const std::vector<uint32_t> &ima
     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;
+            assert(cx<img_w && cy<img_h);
+            img[cx + cy*img_w] = color;
+        }
+    }
+}
+
 int main() {
     const size_t win_w = 512; // image width
     const size_t win_h = 512; // image height
     std::vector<uint32_t> framebuffer(win_w*win_h, 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   0   11100  0"\
+                       "0   0   0      0"\
+                       "0   0   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
+
     for (size_t j = 0; j<win_h; j++) { // fill the screen with color gradients
         for (size_t i = 0; i<win_w; i++) {
             uint8_t r = 255*j/float(win_h); // varies between 0 and 255 as j sweeps the vertical
@@ -43,6 +75,17 @@ int main() {
         }
     }
 
+    const size_t rect_w = win_w/map_w;
+    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;
+            draw_rectangle(framebuffer, win_w, win_h, rect_x, rect_y, rect_w, rect_h, pack_color(0, 255, 255));
+        }
+    }
+
     drop_ppm_image("./out.ppm", framebuffer, win_w, win_h);
 
     return 0;