3 files changed, 32 insertions, 1 deletions
diff --git a/README.md b/README.md
index 9bafdf2..ef15bbe 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # sqlite creative coding
 
-Generating some visuals with SQL because nobody stopped me
+Generating some visuals with SQL because nobody stopped me. With the magic of [recursive CTE](https://sqlite.org/lang_with.html).
 
 ### Dependencies
 - sqlite3
@@ -26,5 +26,12 @@ Generating some visuals with SQL because nobody stopped me
       <img src="media/mandelbrot.png" />
     </td>
   </tr>
+  <tr>
+    <td width="50%" valign="top">
+      <h3><a href="./src/polka.sql">Just some dots</a></h3>
+      <img src="media/polka.png" />
+    </td>
+    <td width="50%" valign="top"></td>
+  </tr>
 </table>
 
diff --git a/media/polka.png b/media/polka.png
new file mode 100644
index 0000000..c15804b
--- /dev/null
+++ b/media/polka.png
diff --git a/src/polka.sql b/src/polka.sql
new file mode 100644
index 0000000..3d72540
--- /dev/null
+++ b/src/polka.sql
@@ -0,0 +1,24 @@
+INSERT OR REPLACE INTO images (id, width, height) VALUES ('polka', 400, 400) RETURNING id;
+
+WITH RECURSIVE
+  image AS (SELECT *, width/10 AS gapx, height/10 AS gapy, 16.0 AS size FROM images WHERE id = 'polka'),
+  horizontal(x) AS
+    (SELECT width FROM image UNION ALL SELECT x - 1 FROM horizontal WHERE x > 1),
+  vertical(y) AS
+    (SELECT height FROM image UNION ALL SELECT y - 1 FROM vertical WHERE y > 1),
+  dotsx(dotx, column) AS (
+    SELECT 0, 0 UNION ALL
+    SELECT dotx + gapx, column + 1 FROM dotsx, image WHERE dotx < width
+  ),
+  dotsy(doty, row) AS (
+    SELECT 0, 0 UNION ALL
+    SELECT doty + gapy, row + 1 FROM dotsy, image WHERE doty < height
+  ),
+  _pixels(x, y, r, g, b) AS (
+    SELECT x, y,
+      IFNULL((SELECT 60 * abs((row % 5) - (column % 5)) FROM dotsx, dotsy
+        WHERE POW(x - dotx - gapx*(row%2)/2.0, 2) + POW(y - doty, 2) < size*size LIMIT 1), 0),
+      50, 70
+    FROM vertical, horizontal, image
+  )
+INSERT INTO pixels (image_id, x, y, r, g, b) SELECT 'polka', x, y, r, g, b FROM _pixels;